I've been trying to rebuild my 1948 8N. I decided I didn't need to turn the crank as the bearings and crank looked fine. I bought new bearings anyway and just stayed with the same size as the old ones.010 After ordering everything I have now noticed a couple of the old bearing have shims. To top it off the shims are made of news paper. Looks as if the farmer that had this before new what he was doing but didn't have the money to buy real shims. Maybe this was common practice back in the day. Well here's my question....what do I do now? I'm thinking just cut some news paper, soak the strips in motor oil and slap them in there like paper mache? Bolt the thing back together and get ready for hay season.
- Thread starter GOLDPAN6
- Start date
Ultradog MN
Well-known Member
- Location
- Twin Cities
I would not just arbitrarily add shims.
I would use plastigage to check your bearing clearance. You may or may not need shims as the crank could have worn slightly since those old bearings were installed and you want them a bit tighter now.
I don't know if you are familiar with using plastigage but would start by torquing your caps down with no shims and see what the plastigage says.
I have never heard of using paper for shims but have installed rod bearings that included brass shims to get the correct clearance.
If you do need shims I think I would use brass shim stock. Find out what thickness/s you need and ask for some shim stock at your local machine shop.
I think I would also ask about using paper shims over on tractor talk board where the knowledge base is vastly greater than here.
See what they say about paper. My thought is paper might crush but maybe it wouldn't.
Tractor Talk
I would use plastigage to check your bearing clearance. You may or may not need shims as the crank could have worn slightly since those old bearings were installed and you want them a bit tighter now.
I don't know if you are familiar with using plastigage but would start by torquing your caps down with no shims and see what the plastigage says.
I have never heard of using paper for shims but have installed rod bearings that included brass shims to get the correct clearance.
If you do need shims I think I would use brass shim stock. Find out what thickness/s you need and ask for some shim stock at your local machine shop.
I think I would also ask about using paper shims over on tractor talk board where the knowledge base is vastly greater than here.
See what they say about paper. My thought is paper might crush but maybe it wouldn't.
Tractor Talk
Richard G.
Well-known Member
I used layers of aluminum foil many years ago on one bearing of a MH 101SR.
Pulled my sawmill for years like that. Had the Continental F226 engine in it.
Richard in NW SC
Pulled my sawmill for years like that. Had the Continental F226 engine in it.
Richard in NW SC
Ultradog MN
Well-known Member
- Location
- Twin Cities
The aluminum foil is a good idea.
Hadn't thought of that.
Hadn't thought of that.
Roger in Iowa
Well-known Member
If the crank has worn, you may need more shims, not less. No experience. Use plastigage.
Tall T
Well-known Member
All the main bearings in my 235 Chev were meant to be shimmed but the brass shims are between cap and block not behind the bearing shells so good luck with that.
Like UD said, use plastigage first before adding any brass shim stock or aluminum and strips which would have to be added to both halves of the bearing shell -- and you should know what the thickness of your shim stock is.
In my case I would add say, three .001 brass shims to each of the cap mating faces, plastigage, remove .001 from both sides and plastigage again. After that intense procedure my main clearances ended up at .0017 each.
Like UD said, use plastigage first before adding any brass shim stock or aluminum and strips which would have to be added to both halves of the bearing shell -- and you should know what the thickness of your shim stock is.
In my case I would add say, three .001 brass shims to each of the cap mating faces, plastigage, remove .001 from both sides and plastigage again. After that intense procedure my main clearances ended up at .0017 each.
Everything has been bought for this tractor rebuild last year. I don't want to start buying more parts when I don't need to. With the main bearings being of clamshell design and finding news paper shim only under one half, I would conclude the installer was trying to center the bearings more evenly around the shaft. I don’t think this would tighten up tolerance or change the tolerance. With the clamshell bearing tightened down the area of space is what it is. I don’t see how doing this gives you tighter tolerance, only more even tolerance.
Am I correct with my assessment?
Am I correct with my assessment?
I find it amazing that so many people jump to turning down the shaft every time they open up an engine. Let me fill you in on last years progress. The tractor dropped a sleeve and after inspection it was found that a plugged galley was to blame. The tolerance of the crank was consistent with being turned down .010 and was in good shape. The bearings that were in it didn’t even show signs of wear. The plastiguage worked as it should and the tolerances were in spec +-.002. A decision was made at that time to clean out the oil galleys and rebuild the tractor as is. Turning the crank and buying new bearings again does not change anything except a crank that’s now .020 with a shorter life.
It is quite possible that the two of the bearing seats in the block are a bit lower and was shimmed to center the bearings to the shaft. A newly turned shaft and bearing won’t center itself no matter how many times you turn it.
It is quite possible that the two of the bearing seats in the block are a bit lower and was shimmed to center the bearings to the shaft. A newly turned shaft and bearing won’t center itself no matter how many times you turn it.
TheOldHokie
Well-known Member
- Location
- Myersville, MD
Here is what I think. Insert journal bearings are designed to be a precise precision fit inside a [b:1a35a30108]ROUND[/b:1a35a30108] bore. When torqued to specification they are, by design, crushed and form an out of round oil clearance. That out of round shape is critical in the development of the hydrodynamic pressure differential that keeps a heavily loaded crankshaft running on an oil film.
Automotive machine shops make well deserved money measuring accurately and getting that geometry right. Tinkering with paper shims and nebulous plastigage measurements is a recipe for early bearing failure.
TOH
I went to the mechanist and talked to him about this. He told me that newspaper shims was an old timer trick to quite knocking. Often used to sell an old tractor to some nitwit like me.
He said the crank has only been turned once so the best option is to turn it to .020 and put in new bearings.
After that it?s just bolting everything to spec. No plastiguage, No shims and No guessing. Cost is $175 to turn the crank plus $80 for another set of bearings. Guess I will try and sell the complete set of .010 brand new bearings. I don?t know why I am so stubborn about wanting to do things cheap. Poor people have poor ways I guess. Thank you all for the advice.
He said the crank has only been turned once so the best option is to turn it to .020 and put in new bearings.
After that it?s just bolting everything to spec. No plastiguage, No shims and No guessing. Cost is $175 to turn the crank plus $80 for another set of bearings. Guess I will try and sell the complete set of .010 brand new bearings. I don?t know why I am so stubborn about wanting to do things cheap. Poor people have poor ways I guess. Thank you all for the advice.
TheOldHokie
Well-known Member
- Location
- Myersville, MD
If he didn't actually measure the crankshaft, rods, and the block he is guessing and would be off my list of machinists.
Take block, rods, and crankshaft to a machinist/shop that will measure before machining. Ask for journal AND bore measurements of diameter, taper and out of round for [u:7a38275668]all[/u:7a38275668] journals and bores. Not just an opinion of what needs to be done but measurements to back it up. No one can reliably decide what needs to be done without that data and if he has it he should share it with the customer. Grinding the crankshaft and bolting new bearings into an unknown block and connecting rods is pure guesswork. Personally I do not pay for guesswork because all to often it turns out badly = more cost and aggravation than paying to have it done right the first time.
TOH
Ultradog MN
Well-known Member
- Location
- Twin Cities
Ok. We have more and better info this
evening.
When I posted this morning I did not realize
we were talking about main bearings.
I thought we were talking about rod bearings
as those are the ones that were most often
shimmed back in the day. And I did not
realize we had shimmed the bearing. I
thought we were shimming the cap.
So disregard what I posted below.
The newspaper may have been installed to
compensate for too big of a bearing or too
small of a journal. If you filed about .0005
off the ends of both bearing shells and
added a .002 shim between the bearing and
cap or block you would tighten up that
bearing.
A guy could measure the journals to see what
size they actually are.
He could also measure the the mains with
bearing installed and caps torqued to spec.
That's IF he has the measuring tools and the
skill to use them accurately.
Some people want to trash talk plastigage.
Let them.
There are millions of engines that have been
assembled using that stuff as an indicator
of clearance and they are running just fine.
I agree that too many people just don't know
what they are doing and cart their engine
off to the machine shop for a reman.
A guy who does understand engines and is
willing to tinker can make one of these low
reving engines last a long time on the
cheap.
I would have no qualms about shimming a
bearing on one of these engines. Dunno about
using newspaper but whoever did that was
right in that it worked.
evening.
When I posted this morning I did not realize
we were talking about main bearings.
I thought we were talking about rod bearings
as those are the ones that were most often
shimmed back in the day. And I did not
realize we had shimmed the bearing. I
thought we were shimming the cap.
So disregard what I posted below.
The newspaper may have been installed to
compensate for too big of a bearing or too
small of a journal. If you filed about .0005
off the ends of both bearing shells and
added a .002 shim between the bearing and
cap or block you would tighten up that
bearing.
A guy could measure the journals to see what
size they actually are.
He could also measure the the mains with
bearing installed and caps torqued to spec.
That's IF he has the measuring tools and the
skill to use them accurately.
Some people want to trash talk plastigage.
Let them.
There are millions of engines that have been
assembled using that stuff as an indicator
of clearance and they are running just fine.
I agree that too many people just don't know
what they are doing and cart their engine
off to the machine shop for a reman.
A guy who does understand engines and is
willing to tinker can make one of these low
reving engines last a long time on the
cheap.
I would have no qualms about shimming a
bearing on one of these engines. Dunno about
using newspaper but whoever did that was
right in that it worked.
Ultradog MN
Well-known Member
- Location
- Twin Cities
That's good advice for an expensive engine
TOH. But for a cheap N engine it's overkill.
I'll bet not one in twenty of these engines
that go to the machine shop get that kind of
white glove treatment.
It's too expensive. They were made to be
overhauled in the field by farmers - slap
bearing shells in them and get another
couple of seasons out of it. If someone
wishes to treat them so daintily, have at
it. But they will still do a lot of work for
a long time with the crudest of overhauls.
TOH. But for a cheap N engine it's overkill.
I'll bet not one in twenty of these engines
that go to the machine shop get that kind of
white glove treatment.
It's too expensive. They were made to be
overhauled in the field by farmers - slap
bearing shells in them and get another
couple of seasons out of it. If someone
wishes to treat them so daintily, have at
it. But they will still do a lot of work for
a long time with the crudest of overhauls.
Hobo,NC
Well-known Member
- Location
- Sanford, NC
I think you are forgetting these engines are 70 years old and well pass a shim job... What got them this far wuzzzzzz the original white glove treatment. I don't care how he does it I do care he knows the correct way what he does after that is his call...
What I get out of this the original were in great condition well put'em back in it they have proved they were good and probably better than a guess at what it needs..
As far as turning the shaft you can turn it till you run out of replacement sizes .040 seams to be the stopping point for replacements.
if you could get 100 I would have no problem going .100....
What I get out of this the original were in great condition well put'em back in it they have proved they were good and probably better than a guess at what it needs..
As far as turning the shaft you can turn it till you run out of replacement sizes .040 seams to be the stopping point for replacements.
if you could get 100 I would have no problem going .100....
TheOldHokie
Well-known Member
- Location
- Myersville, MD
Nonsense - good engine shops don't guess or take things for granted.
I don't build engines for a living but if you walked through the door of my shop with an 8N crankshaft I could give you complete crankshaft journal dimensions, including taper and out of round in 15-20 minutes. If you are already dead set on regrinding the crank that would be a waste of time since those measurements are part of the QC on the finished crank.
Block main bearing housing and con rod big end bore measurements would take a bit longer because while I do have a decent bore gauge unlike a professional engine shop I am not setup to do that sort of measurement at the drop of a hat.
Any commercial engine shop should be able to measure everything in an 8N lower end for no more than the cost of an hour's labor. Around here that would be about a $100 and likely would be "forgiven" if you let the shop do all of the needed machine work.
Here we have an engine that has been farmerized to death. There is no way of knowing what is wrong in that lower end without taking some good measurements - measurements you simply cannot get with plastigage. Maybe the PO decided to put an engine together with caps borrowed from another engine and tried to "fix" the ensuing problems with newspaper shims. There may be nothing wrong or there may be all sorts of things wrong and just because you get a good plastigage oil clearance measurement when reassembled with a freshly ground crank and new bearings doesn't mean everything in that journal is good to go. Spend the money and measure. Or save yourself $100 and just hope 80 years of hard wear and crude farmerization has left the original dimensions intact.....
TOH
Ultradog MN
Well-known Member
- Location
- Twin Cities
Nonsense?
As you wish TOH.
But your ipse dixit statements do not make
it so.
This board is for the free exchange of
information.
Opinions may vary. They might be opposed to
one another.
That's ok.
Let the people read both sides and then
choose what's best for them and their
wallet.
As you wish TOH.
But your ipse dixit statements do not make
it so.
This board is for the free exchange of
information.
Opinions may vary. They might be opposed to
one another.
That's ok.
Let the people read both sides and then
choose what's best for them and their
wallet.
Mic the crank, if it's .010 under and not scratched or scored you're not gaining anything by turning it to .020. Since the crank is out of the block lay a straightedge across the main bearing journals and see if they all touch the straightedge. If they don't you can buy a brand new standard crank and you'll still have the same problem. If you don't have someone that can Measure the inside diameter of the bearings while installed in block then use platigauge. Clearances are clearances, don't guess.
I'd like to know how an oil galley caused a dropped sleeve.
Tall T
Well-known Member
Goldfinger,
There was a very long standing machine shop in Victoria, R. Angus with machinists who were the age we are now, that were mentors to me.
When I told Bill that my first ever total rebuild 235 came with shimmed main caps from the factory he says, "Hang on a sec!"
He goes up the old blackened wooden stairs to the machine shop upper deck and comes down with 1940's and 50ès pre cut brass shims cut to fit Main Bearing Caps !!
Actually, they didn't all fit. . . I still had to make some thinner ones too and making number 4 with the locating dowels was fun I'm not sure what the best backing would be to punch holes in thin brass . . . a brass block? Hardwood isn't enough to make a one or two shot clean cut. Doh!
Had to body hammer them shims flat afterwards.
Luckily for y'all this was the way before the digital jpeg era
so I have no circles and arrows, and no paragraph on each TIFF, describing what each one was,
to be used as evidence against us.
name that tune*
clue: Arlo
There was a very long standing machine shop in Victoria, R. Angus with machinists who were the age we are now, that were mentors to me.
When I told Bill that my first ever total rebuild 235 came with shimmed main caps from the factory he says, "Hang on a sec!"
He goes up the old blackened wooden stairs to the machine shop upper deck and comes down with 1940's and 50ès pre cut brass shims cut to fit Main Bearing Caps !!
Actually, they didn't all fit. . . I still had to make some thinner ones too and making number 4 with the locating dowels was fun I'm not sure what the best backing would be to punch holes in thin brass . . . a brass block? Hardwood isn't enough to make a one or two shot clean cut. Doh!
Had to body hammer them shims flat afterwards.
Luckily for y'all this was the way before the digital jpeg era
so I have no circles and arrows, and no paragraph on each TIFF, describing what each one was,
to be used as evidence against us.
name that tune*
clue: Arlo
deanostoybox
Member
You can get anything you want... excepting Alice
Ultradog MN
Well-known Member
- Location
- Twin Cities
Well Mr. Kettle,
Do you have some advice for Goldpan or are
you just here to do your usual stirring the
pot?
Do you have some advice for Goldpan or are
you just here to do your usual stirring the
pot?
Don't overanalyze it. Machine shop guy has seen a thousand of them if he has seen one. He will measure before he grinds, no doubt. As a side note. My John Deere A has main bearing shims. And my AC model B has rod bearing shims. . But for rhis application, have the machinist grind it is best. You on the right track
When I was in high school, I worked at the airport in town. The guy overhauled aircraft engines and airframes. Real precise and serious work. The man was a stickler for doing it right. He used plastigage as an initial indicator of bearing clearances. This was 50 years ago. I don't see why some e would loose their shirt over using it in an automotive application.
TheOldHokie
Well-known Member
- Location
- Myersville, MD
Depends. If you are shimming behind the shells as the PO of this tractor did you need more. If shimming the parting line of the block and cap as some older engine designs did you need less.
In either case shimming modern two piece insert bearings adversely effects all the expensive engineering and design work that went into their geometry. They are generally designed to fit a [b:6f9b308264][u:6f9b308264]dead round[/u:6f9b308264][/b:6f9b308264] block or rod bore with a diameter tolerance of +/-.0005 and a carefully controlled clamping load. Putting shims anywhere detrimentally alters their installed geometry with a decrease in the effectiveness of the hydro-dynamic oil film that geometry produces. In plain words - they don't work nearly as well. But hey - what makes the bearing engineers at places like Clevite, Mahle, Federal Mogul, Sealed Power, etc. think they know more about engine bearings than old farmers or engine designers back in the 40's :roll:
TOH
Tall T
Well-known Member
TOH,
Not disagreeing at all but just saying that in the case of my 1976 235 rebuild with the shimmed main caps, I [b:64b6f154ae]first[/b:64b6f154ae] had the crank ground to the correct undersize and bought the appropriate bearings . . . THEN I used Plastigage.
As i said, I wound up with .0017 clearances on each of my mains and my engine today still has 48 psi factory oil pressure.
T
Not disagreeing at all but just saying that in the case of my 1976 235 rebuild with the shimmed main caps, I [b:64b6f154ae]first[/b:64b6f154ae] had the crank ground to the correct undersize and bought the appropriate bearings . . . THEN I used Plastigage.
As i said, I wound up with .0017 clearances on each of my mains and my engine today still has 48 psi factory oil pressure.
T
TheOldHokie
Well-known Member
- Location
- Myersville, MD
(quoted from post at 15:29:40 05/12/18) TOH,
Not disagreeing at all but just saying that in the case of my 1976 235 rebuild with the shimmed main caps, I [b:49fa149f8a]first[/b:49fa149f8a] had the crank ground to the correct undersize and bought the appropriate bearings . . . THEN I used Plastigage.
As i said, I wound up with .0017 clearances on each of my mains and my engine today still has 48 psi factory oil pressure.
T
Your engine is somewhat unique in that it was built with caps designed to be shimmed. That is not the norm but what the OEM decided to do. The vast majority of engines were not designed that way and will benefit from proper fitment without shimming - the L-head being just one of many.
My point from the start has been that Plastigage is not a substitute for proper inspection of the block main and rod big end bores and will not reveal real problems there that a proper inspection with good instruments will.
Plastigage is not as reliable or accurate at measuring oil clearances as measurement with a bore gage and micrometer. But absent those instruments Plastigage is a perfectly acceptable way to perform a [u:49fa149f8a][b:49fa149f8a]final[/b:49fa149f8a][/u:49fa149f8a] check of oil clearance after all of the other issues have been dealt with.
TOH
Ultradog MN
Well-known Member
- Location
- Twin Cities
These engines are not complicated.
One need not be a highly skilled machinest
to understand their concept.
I worked in a big engine shop for about 9
months back in the 1980s. Was their welder.
I left because they didn't pay enough.
I watched a lot of engines come through that
place. Watched them get line bored, decked,
cylinders bored, cranks ground, cams
reshaped, rods reconditioned, etc, etc.
It did not take long to understand the
rather simple machine functions that were
being done to these engines.
Do I have the skills to perform these
functions on those machines? Of course not.
That takes skill and skill takes time and
experience.
But the concepts were not complicated.
The idea of a lathe or mill, a line boring
mill or a crank welder is rather simple.
To the uninitiated this stuff may all seem
like wizardry. To the guy who hasn't been
exposed to close tolerances it may seem like
magic. But it is not magic or wizardry.
Intellectually it is all very simple stuff.
An intelligent butcher, baker or even a
carpenter can understand the concepts of
machining or engines just as well as a
highly skilled machinist.
This board has a tendancy to elevate to god
like status those who can tell them how to
polerize a generator because they have no
understanding of the concept.
Likewise they seem to elevate those who can
answer machining questions.
But you yourself know that understanding how
and why to polarize does not make a guy
special or brilliant. Nor does having a
lathe and mill make a guy smarter than
everyone else here.
The skills to do things accurately and
efficiently may take years to develop. But
the ideas - the concepts - are rather simple
after all.
One need not be a highly skilled machinest
to understand their concept.
I worked in a big engine shop for about 9
months back in the 1980s. Was their welder.
I left because they didn't pay enough.
I watched a lot of engines come through that
place. Watched them get line bored, decked,
cylinders bored, cranks ground, cams
reshaped, rods reconditioned, etc, etc.
It did not take long to understand the
rather simple machine functions that were
being done to these engines.
Do I have the skills to perform these
functions on those machines? Of course not.
That takes skill and skill takes time and
experience.
But the concepts were not complicated.
The idea of a lathe or mill, a line boring
mill or a crank welder is rather simple.
To the uninitiated this stuff may all seem
like wizardry. To the guy who hasn't been
exposed to close tolerances it may seem like
magic. But it is not magic or wizardry.
Intellectually it is all very simple stuff.
An intelligent butcher, baker or even a
carpenter can understand the concepts of
machining or engines just as well as a
highly skilled machinist.
This board has a tendancy to elevate to god
like status those who can tell them how to
polerize a generator because they have no
understanding of the concept.
Likewise they seem to elevate those who can
answer machining questions.
But you yourself know that understanding how
and why to polarize does not make a guy
special or brilliant. Nor does having a
lathe and mill make a guy smarter than
everyone else here.
The skills to do things accurately and
efficiently may take years to develop. But
the ideas - the concepts - are rather simple
after all.
I hate coming to this site. Every time I come here I find enough testosterone to make my tractor run all by itself. I stopped in last fall to talk about this rebuild and found the advice all over the map as arguing ensued so the tractor just sits.
When I started this project I went to the mechanist in my area and was quoted $1500 to rebuild the engine. Simply put it was over my budget.
As a former machinist mate in the navy and a long history of turning wrenches for a living I decided to rebuild the little engine myself. It can’t be that difficult, with all kinds of father and son 8N rebuilds on youtube.
Seems to me there are two groups of people on this site, those that make profit professionally rebuilding tractors for people and those that have the can do attitude and willing to get dirty themselves. I am of poor means so that puts me in the later category.
I bought this tractor from an auction and didn’t know it had engine damage. When I took this tractor apart I found it had dropped the number one sleeve and destroyed the piston. Upon further inspection I found that all the oilier holes in the connecting rods were plugged up with crud. The pan had two inches of crud in it and I cleaned out a lot of crud in the oil galleys. (Note to self, drop the oil pan from time to time for cleaning and inspection) My assessment was the piston was starved of oil leading to its demise.
Now from my inspection of the crank I found it to be in very good shape. Measurements of the main journals were 2.238 +-.002. Keep in mind I am using your everyday standard calipers so the +-.002 might just be me. Pretty sure this crank is fine. I did shine up journals with 2000 grit wet and dry and shoelace. Now right there, I know some on this site are swinging from the chandeliers shaking their fist in protest…let me assure you, it will be ok. It’s not a 69 Camaro.
Because I went through all this last fall and since that time was when I found two bearings with news paper shims I will do the measurements again.
1 I assume I will be using plastiguage on dry bearings and shaft.
2 Is there a reason to use the plasiguage under the bearing between the block?
3 Do I need to put in the front and rear seals while doing this?
There was mention of taking the block, crank, connecting rods, all bearings and a tire to the mechanist. Problem is this start getting into him rebuilding this tractor. He already quoted me for that job and I was unwilling to do that.
OldHokie, I believe I bought the sleeve tools from you. I’ve already installed the new sleeves. I’ve bought a solvent tank and done all the necessary cleaning of the parts, internal engine areas and purchased way more replacement parts for this tractor then I ever wanted too. I’m just trying to get through it and be done with it. I have a farm to run and need my garage and barn back. Simple instructions and advice works best
When I started this project I went to the mechanist in my area and was quoted $1500 to rebuild the engine. Simply put it was over my budget.
As a former machinist mate in the navy and a long history of turning wrenches for a living I decided to rebuild the little engine myself. It can’t be that difficult, with all kinds of father and son 8N rebuilds on youtube.
Seems to me there are two groups of people on this site, those that make profit professionally rebuilding tractors for people and those that have the can do attitude and willing to get dirty themselves. I am of poor means so that puts me in the later category.
I bought this tractor from an auction and didn’t know it had engine damage. When I took this tractor apart I found it had dropped the number one sleeve and destroyed the piston. Upon further inspection I found that all the oilier holes in the connecting rods were plugged up with crud. The pan had two inches of crud in it and I cleaned out a lot of crud in the oil galleys. (Note to self, drop the oil pan from time to time for cleaning and inspection) My assessment was the piston was starved of oil leading to its demise.
Now from my inspection of the crank I found it to be in very good shape. Measurements of the main journals were 2.238 +-.002. Keep in mind I am using your everyday standard calipers so the +-.002 might just be me. Pretty sure this crank is fine. I did shine up journals with 2000 grit wet and dry and shoelace. Now right there, I know some on this site are swinging from the chandeliers shaking their fist in protest…let me assure you, it will be ok. It’s not a 69 Camaro.
Because I went through all this last fall and since that time was when I found two bearings with news paper shims I will do the measurements again.
1 I assume I will be using plastiguage on dry bearings and shaft.
2 Is there a reason to use the plasiguage under the bearing between the block?
3 Do I need to put in the front and rear seals while doing this?
There was mention of taking the block, crank, connecting rods, all bearings and a tire to the mechanist. Problem is this start getting into him rebuilding this tractor. He already quoted me for that job and I was unwilling to do that.
OldHokie, I believe I bought the sleeve tools from you. I’ve already installed the new sleeves. I’ve bought a solvent tank and done all the necessary cleaning of the parts, internal engine areas and purchased way more replacement parts for this tractor then I ever wanted too. I’m just trying to get through it and be done with it. I have a farm to run and need my garage and barn back. Simple instructions and advice works best
For this type of measuring, calipers are not your best choice, Outside mics are needed. When I did one of mine 6 years ago I found some mics on craigslist. not only do you need size of the journals but you need to make sure they are round, .
your questions:
#1 I did mine dry
2: since that is where your paper shims were, I would say yes.
#3 I would do it all without the oil seals, put them in when you get the bearings all figured out.
My opinions only! some on here will probably have different ideas, but that is what you get on forums.
I have watched how to videos on youtube that were totally wrong and some that were good.
Ultradog MN
Well-known Member
- Location
- Twin Cities
You are correct jmor.
It is all very easy. All of it.
I have about 5 years of machine shop experience counting the Navy so not that much.
But it did teach me enough of the basics so I could go on to do what I do now.
It is all very easy. All of it.
I have about 5 years of machine shop experience counting the Navy so not that much.
But it did teach me enough of the basics so I could go on to do what I do now.
TheOldHokie
Well-known Member
- Location
- Myersville, MD
Here is simple advice - about as simple as it gets:
If the journal diameters vary +/- .002 it would mean the main journals measure 2.236 to 2.240 which is way out of factory specification (2.2380/2.2390) and needs to be reground. Is that really what you meant and if not what did you mean? And as Mr. Geiger says you need a micrometer not calipers to get reliably accurate measurements.
Engine shops generally don't like doing piece work and you don't always get the finest of service when they do. If you do have the crankshaft reground measure it when you get it back.
Your mains are currently .010 under and .020 under should measure 2.2280/2.2290, with a max of .001 taper and out of round.
Assuming the crankpins are also reground .020 under they should measure 2.0735/2.0745 with the same taper and out of round limits.
Plastigauge is used to measure vertical oil clearance and should be laid across the middle of each journal at 90* to the parting line. The bearing cap with insert installed is then bolted up and torqued to specification, then removed, and the width of the smashed plastigage is compared to the reference scale on the plastigage package to determine the oil clearance indicated.
Connecting rod vertical oil clearance should be .0009/.0030
Main bearing vertical oil clearance should be .0005/.0029
TOH
Hobo,NC
Well-known Member
- Location
- Sanford, NC
I can tell ya it hurts real bad with things go wrong. Even worst when it could have been avoided...
Just encase no one thanks ya for the lessons "Thank ya thank ya very much"
The FO-4 that I have states the diameter from factory is 2.248-2.249. This crank was taken down .010 and all bearing taken out of it were .010 bearings. Now the way I see it is .010 from 2.248 = 2.238. Which is what I come up with. The manual gives a range of .005 so I think .002 qualifies as being in spec. Don’t know where you’re getting those numbers as I am looking at the manual right now. I am rechecking my measurements now with plasiguage. I’m am trying to figure out why the previous owner used some news print under two bearings on one side. It might be that there was no reason for it in the first place.
TheOldHokie
Well-known Member
- Location
- Myersville, MD
My numbers are from the Clevite catalog but they match the FO-4 numbers. You are a little confused on how linear tolerances are specified:
- [*:c577a114a2]The FO-4 factory tolerance of 2.248-2.249 would be the same as 2.2485 +/- .0005[*:c577a114a2]Your tolerance of 2.238 +/- .002 is is the same as 2.236-2.240 - probably not what you meant or what you measured.[*:c577a114a2]The .005 number in the FO-4 is the wear limit (maximum acceptable oil clearance) for a any main journal. I don't know about you but I would never assemble an engine where the oil clearance of any jornal was already at or even near the wear limit.[/list:c577a114a2]So remeasure your crankshaft journals and tell us the largest and smallest diameter you get. Taper and out of round for each journal are also important numbers.
Keep in mind a typical dial or digital caliper has an accuracy of +/- .001 so it isn't accurate enough to reliably measure a 2.238/2.239 specification. The potential measurement error is greater than the allowable tolerance. If you want to evaluate crankshaft journals you really should spend $25-$30 for an inexpensive 2-3" outside micrometer that has a tenths vernier.
TOH
I do appreciate your input and I’m not going to reassemble before I know it’s right. I might be a slow learner but I’m not foolish. Still working the problem.
I don’t think the mechanist was steering me wrong. I know he is a good mechanist and has work lined up to no end. I think his approach of bringing him the crank and having him turn it to .020, buy all new .020 bearings and put it back together was not bad advice. He understands I am poor and can’t bring him the tractor engine to rebuild. He has rebuilt many 8N’s over the 40 years he has been there and realizes this is not NASA engineering. He does have the appropriate measuring tools. He said if it didn’t need to be turned down he would charge me $25 for his assessment. Other wise it’s $175 to make the crank right. His personal note was forget shims and start with factory measurements and go from there. After that, bolt everything back together and free myself from this headache.
I don’t think the mechanist was steering me wrong. I know he is a good mechanist and has work lined up to no end. I think his approach of bringing him the crank and having him turn it to .020, buy all new .020 bearings and put it back together was not bad advice. He understands I am poor and can’t bring him the tractor engine to rebuild. He has rebuilt many 8N’s over the 40 years he has been there and realizes this is not NASA engineering. He does have the appropriate measuring tools. He said if it didn’t need to be turned down he would charge me $25 for his assessment. Other wise it’s $175 to make the crank right. His personal note was forget shims and start with factory measurements and go from there. After that, bolt everything back together and free myself from this headache.
I've taken apart more than one engine that had leather shims.
Never seen newspaper ones though. These are low compression,
low RPM engines so it apparently worked fine. Hard to believe
they didn't disintegrate with the moisture, heat and pressure.
I rebuilt my 8N engine over this past winter.
I paid my local machinist to handle the block work as well as grinding the crank.
He also did the entire valve train. Ground the valves, seats, seals, etc.
He and I have a 10 year or more successful history on engines from 10
to 600+ HP so I trust him, but I still check all the clearances when
I reassemble them. With that kind of history, Plastigauge is enough for me.
If, and I do mean if, you could trust your local machinist to do the kind
of work that my machinist and I did on my 8N engine, a $1500 rebuild
would be cheap. And it would be far less frustration all the way around.
Sometimes, the frugal man spends the most.
Never seen newspaper ones though. These are low compression,
low RPM engines so it apparently worked fine. Hard to believe
they didn't disintegrate with the moisture, heat and pressure.
I rebuilt my 8N engine over this past winter.
I paid my local machinist to handle the block work as well as grinding the crank.
He also did the entire valve train. Ground the valves, seats, seals, etc.
He and I have a 10 year or more successful history on engines from 10
to 600+ HP so I trust him, but I still check all the clearances when
I reassemble them. With that kind of history, Plastigauge is enough for me.
If, and I do mean if, you could trust your local machinist to do the kind
of work that my machinist and I did on my 8N engine, a $1500 rebuild
would be cheap. And it would be far less frustration all the way around.
Sometimes, the frugal man spends the most.
TheOldHokie
Well-known Member
- Location
- Myersville, MD
OK - there you go. Take the crank to the machinist and have him measure it. That way you will "know" half the equation and can hope for the best on the other half. When you get the crank back from the machinist and you reassemble the mains if your plastigaged clearances come out in the .0005/.002 range you can be reasonably confident everything is fine. If the come out larger or smaller something is still wrong. Either the crank (reground or not) is off, the block bore is off, and/or your plastigaged measurements are off.
TOH
TheOldHokie
Well-known Member
- Location
- Myersville, MD
Over the years I have been as frugal as they come but I have never flinched at buying tools when the job at hand made financial sense. You can't turn your crank but what you can do is purchase and learn how to use a micrometer for the same cost your machinist is going to charge you for a one off crankshaft evaluation.
These are not the finest measuring instruments in the world but based on my experience if cared for and kept calibrated these ubiquitous Taiwanese micrometers will reliably split a thou and tell you everything you need to know about those journals. Ten plus years ago I bought a boxed set of 4 (0-4") for something like $60 and three of them are still in my tool chest alongside some higher end Starretts and Mitutoyos. I had to scrap the 3-4" one because I dropped it and chipped the carbide anvil on the thimble. That was on me not the tool :evil:
2-3" Outside Micrometer ($25)
TOH
Hobo,NC
Well-known Member
- Location
- Sanford, NC
They were made to be
overhauled in the field by farmers
You have been hang'N out on the N board to long...
That is a made up statement and you know it. If that were true they would have put a zipper on the engine are made ware parts adjustable. The fact that they are of a low RPM engine also has nuttin to do with it they can turn double the RPM and live just as long a life. The RPM is governed because it would be a run away train if it were not.
overhauled in the field by farmers
You have been hang'N out on the N board to long...
That is a made up statement and you know it. If that were true they would have put a zipper on the engine are made ware parts adjustable. The fact that they are of a low RPM engine also has nuttin to do with it they can turn double the RPM and live just as long a life. The RPM is governed because it would be a run away train if it were not.
TheOldHokie
Well-known Member
- Location
- Myersville, MD
Low RPM and heavy loads are some of the most severe conditions journal bearings typically see. It is RPM and narrow oil clearances that build the thousands of pounds per inch oil film pressure that keeps the load on the crankshaft supported and clear of the bearings. At low RPM the oil film pressure falls and the load starts to force the crankshaft journals into contact with the bearing surface. That shortens bearing and journal life quickly and is why oil clearances need to be kept close to specification.
TOH
Ultradog MN
Well-known Member
- Location
- Twin Cities
And so,
It looks like these guys have talked you into another $1500 engine job.
It seems that's about all they are capable of doing here. Especially when it is your money they're spending.
On a tractor that's probably worth $2K when you are done.
To each his own I guess.
By the way, how long did you run it the way it was? I suspect if not for the piston problem you had it would probably would have run a long time as it was.
It looks like these guys have talked you into another $1500 engine job.
It seems that's about all they are capable of doing here. Especially when it is your money they're spending.
On a tractor that's probably worth $2K when you are done.
To each his own I guess.
By the way, how long did you run it the way it was? I suspect if not for the piston problem you had it would probably would have run a long time as it was.
Tall T
Well-known Member
I wrote this on Saturday and wasn't going to post it, but on second thought.
UD,
You might have to eat crow.
You wrote:
That's good advice for an expensive engine
TOH. But for a cheap N engine it's overkill.
I'll bet not one in twenty of these engines
that go to the machine shop get that kind of
white glove treatment.
It's too expensive. They were made to be
overhauled in the field by farmers - slap
bearing shells in them and get another
couple of seasons out of it. If someone
wishes to treat them so daintily, have at
it. But they will still do a lot of work for
a long time with the crudest of overhauls.
I think this is where your advice fell short and where the adversity ensued:
That fact that a farmer could take a stab at his own fix and partially succeed isn't even close to a testimony that an N engine is cheap; but on the contrary, it is the proof that as Hobo said, these engines initially got the critical-to-performance-and-longevity "white glove treatment" at the factory in terms of design, tolerances and balance. There's no way the engines could have had the snot worked out of them for so many years without having had the best of engine machine specs at play right out of the gate.
"If one wished to treat them so daintily" is also a total mischaracterization, of sensibly approaching rebuilds or refurbs judiciously, fastidiously, with all due respect for machine shop tolerances. Anything less is going to amount to good money after bad, wasted time and a disappointing, oil burning, knocking engine down the road with the owner never sure when the machine will let him down.
Terry
BOB SAID “Also have the main bearing areas checked for size and "out of round, and have the "line bore" checked”
Where exactly is that in the FO-4 manual or the 3730-47J Service manual or the 3729-50-M Operator’s manual?
I also have the book “How to restore Ford Tractors” by Tharran Gaines and although it’s been a year sine I last read it I cant remember seeing what your talking about. Wonder why that is?
Line bore…. Don’t remember reading about this either.
Of the six or eight owners, mechanics and the mechanist I talked to about this tractor, all have expressed to me this is a simple job. Simply installing a complete engine rebuild kit is more care then most of these tractors have ever seen.
They all stated the crank and bearing are important but after that they all just put in the new kit and started driving the tractor. Over thinking, over spending and stressing out over a $1200 tractor is ridiculous and I concur. My JD lawnmower cost more then this 8N.
To TheOldHokie, Thank you for the link to the micrometer. I have used micrometers a lot over the years working on tool and dies and have a nice set of Mitutoyo but they only go out to one inch, that’s why I went to the calipers. I don’t normally work on things bigger then an inch and when I did calipers were used.
You have me perplexed with your “linear tolerances” comment.
Twice you have brought this term into the conversation, once last fall and again the other day. While I am not an auto mechanic I find it hard to believe your talking about bearing tolerances in the ten-thousandths.
Where exactly is that in the FO-4 manual or the 3730-47J Service manual or the 3729-50-M Operator’s manual?
I also have the book “How to restore Ford Tractors” by Tharran Gaines and although it’s been a year sine I last read it I cant remember seeing what your talking about. Wonder why that is?
Line bore…. Don’t remember reading about this either.
Of the six or eight owners, mechanics and the mechanist I talked to about this tractor, all have expressed to me this is a simple job. Simply installing a complete engine rebuild kit is more care then most of these tractors have ever seen.
They all stated the crank and bearing are important but after that they all just put in the new kit and started driving the tractor. Over thinking, over spending and stressing out over a $1200 tractor is ridiculous and I concur. My JD lawnmower cost more then this 8N.
To TheOldHokie, Thank you for the link to the micrometer. I have used micrometers a lot over the years working on tool and dies and have a nice set of Mitutoyo but they only go out to one inch, that’s why I went to the calipers. I don’t normally work on things bigger then an inch and when I did calipers were used.
You have me perplexed with your “linear tolerances” comment.
Twice you have brought this term into the conversation, once last fall and again the other day. While I am not an auto mechanic I find it hard to believe your talking about bearing tolerances in the ten-thousandths.
Hobo,NC
Well-known Member
- Location
- Sanford, NC
No No No old dawg how he are anyone else hacks it up is there call Whut the ell is wrong with knowing the correct way to do it. What kind of metal do folks on the N board get for all there hack tricks....
I can glue tile to a wall it will stick at least till the check clears I am sure you would have something to say about my hack job :wink:
I did think that paper shim was interesting that's why I said if they looked good put'em back in when he said he did not want to spend the money to get it back to OEM spec's... I have BTDT and caused myself more trouble than it was worth I should have put it back just like I found it. It had ran 50K with a shimmed bearing the crank and bearing looked as good as new no oil pressure issues are noise. I made the call to put a haft thousand bearing in it, it ran about 100 miles and spun it
...I got to tow it 100 miles pull the engine and put a crank in it on my dime... Actually I rebuilt the hole dam engine at that time my plan I was not gonna eat it again...
On another note WHY I and others have got away from time consuming jobs like engine work there is not enoufh profit in it. The first though folks would say damm you getting 20 hr to do it. Well I can do small jobs in that 20 hr. and end up with 30 to 80% more total profit with out the liability.
TheOldHokie
Well-known Member
- Location
- Myersville, MD
Your journal tolerance is .001. Your caliper has an accuracy of +/- .001. To measure to within a thousandth you need an instrument with sub-thoisandth accuracy. For this application that would typically be a micrometer with .0001 resolution and sub-thousandth accuracy. Notice i did NOT say .0001 accuracy. And yes, automotive bearing clearances often span a thousandth and will be specified to four decimal places.
TheOldHokie
Well-known Member
- Location
- Myersville, MD
Your journal tolerance is .001. Your caliper has an accuracy of +/- .001. To measure to within a thousandth you need an instrument with sub-thoisandth accuracy. For this application that would typically be a micrometer with .0001 resolution and sub-thousandth accuracy. Notice i did NOT say .0001 accuracy. And yes, automotive bearing clearances often span a thousandth and will be specified to four decimal places.
It’s all about my confusion. I understood the tolerance to be .005 but your saying .001. When you placed the 5 at the end of my measurement of 2.238 being .010 under I was a bit taken back when you wrote 2.2385 you jumped from the thousandths to the ten-thousandths place. If this is correct I can’t possibly measure accurately with calipers. I guess I have a mental block with the tolerances being so small on a 65-year-old tractor. I’m strapped for cash until next week but I will run the crank over to the mechanist for accurate measurements.
TheOldHokie
Well-known Member
- Location
- Myersville, MD
Keep in mind the FO-4 is a pretty minimal manual and lacks a lot of engine specifications and often rounds numbers to three decimal points. Consider that the FO-4 oil clearance specification is .000/.003. If you think about it the FO-4 specification cannot be taken at face value because .000 oil clearance will self destruct in very short order.
IMO a better source for this sort of data is the Ford Tractor Service Specifications manual which was intended for use by Ford dealer service mechanics. If you look there you will find they give:
[b:08a05a5c31]MAIN BEARING OIL CLEARANCE - ALL ENGINES : 0007/.0023[/b:08a05a5c31]
If I look at the Clevite catalog I find yet another number - .0005/.0029. That probably reflects the specific design characteristics of their bearings
Even as far back as 1940 crankshaft grinding was done to tenths accuracy and Ford factory prints are replete with sub thousandth tolerances. They were not striving for .0001 accuracy in their manufacturing processes because it would have been prohibitively expensive. Probably more like +/- .0005 which is enough to manufacture to .001 fits without interference problems from tolerance stack-up.
TheOldHokie
Well-known Member
- Location
- Myersville, MD
You are struggling with a basic concept of measurement science and it's application to manufacturing that is difficult to grasp for many people. Let me try again.
The tolerance in the FO-4 is not .005. That is a oil clearance wear limit for a used engine and at that point it needs to be rebuilt. It is only used to evalute the amount of wear on the journal bearing assembly. It is not a manufacturing tolerance for the crankshaft so forget it.
When building a NEW engine the tolerance on a .010 under crankshaft main journal diameter is 2.238/2.329. That is a manufacturing/grinding/.machining tolerance of .001. If you use calipers that have an ACCURACY of +/- .001 to measure the journal you have potential measurement error of .003. Assume the caliper measurement comes out at 3.238. You don't know if the REAL LIFE physical dimension you measured is 3.237, 3.238, 3.239 or someplace in between. To ensure that your measurement is [b:4b9d4a9506]accurate[/b:4b9d4a9506] to within .001 you need an instrument that can split a thou. So the proper instrument to use is a micrometer with an [b:4b9d4a9506]accuracy[/b:4b9d4a9506] of +/- .0001
TOH
Can't find a date on them but I knew it was news print when I saw page 3 on one. They are as thin as rice paper. Much thinner then bible paper. The threw a couple of the bearings in the trash last fall when I took this apart. Wish I had looked closer then. I wasn't focused on the old bearings as much as I was looking at the crank.
To TheOldHokie,
Thank you for the school lesson. I took the crank to the machinist. He measured it and found that for the most part the crank was ok but did find that one of the rod journals was out .003 with the rest being out .001-,002. He stated this was on the outside tolerances. He also found the same with the main journals. One was out .003 and the others were out .001. In a pinch I could put the crank back in but said this was why the previous owner used paper shims trying to compensate by adding .002. We discussed it and he explained it was time to bring the crank back into tolerance with .020 bearing. He understood I had bought a whole set of .010 bearing with the kit but sometimes you just have to take the hit and start over. So now I'm moving in the right direction and look forward to being done with this job. I'm really starting to not like this tractor but hey, it's only money right? Thank you again for the explanation of linear measurements.
Thank you for the school lesson. I took the crank to the machinist. He measured it and found that for the most part the crank was ok but did find that one of the rod journals was out .003 with the rest being out .001-,002. He stated this was on the outside tolerances. He also found the same with the main journals. One was out .003 and the others were out .001. In a pinch I could put the crank back in but said this was why the previous owner used paper shims trying to compensate by adding .002. We discussed it and he explained it was time to bring the crank back into tolerance with .020 bearing. He understood I had bought a whole set of .010 bearing with the kit but sometimes you just have to take the hit and start over. So now I'm moving in the right direction and look forward to being done with this job. I'm really starting to not like this tractor but hey, it's only money right? Thank you again for the explanation of linear measurements.
TheOldHokie
Well-known Member
- Location
- Myersville, MD
Thanks for the update. FWIW I think I agree with your machinist but it is hard to tell exactly what he found from your description. Simple absolute measurements are the best way to describe the situation because it eliminates all ambiguity. Does "out .001"-.002" mean it was .001-.002 smaller than the minimum factory tolerance of 2.0935"? If so I would not describe that as "on the outside of tolerances" - it is simply out of tolerance by that amount. No matter how you do the arithmetic the .003" number indicates a significantly worn journal that is undersize by at least .002 and regrinding the crankshaft is a good call if you expect to get decent oil clearances with new bearings.
TOH
Well it's not real clear to me either. When I talked to him about the +-005 he simply said it's a half. (same thing you said) After that he said the rod journal was 3 out and that's on the outside. I would have low oil pressure. He had seen people put much worse cranks back in there tractors but the right thing to do was turn the crank and do it right. I don't speak machinist but I think his reference of "Half" was the linear concept you were talking about. At any rate he said he wanted to check the crank to make sure it's not bent first which surprised me. I find it hard to believe you could bend a crank so short and that thick but I just nodded my head as if agreeing. Then he told me not to buy parts until he was finished with it....and have a good day. At that point I just wrapped my head around the idea that this is all good and that spending the $175 was the right thing to do.
TheOldHokie
Well-known Member
- Location
- Myersville, MD
His advice about buying parts prior to thorough engine inspection is dead on. Crankshafts get bent and broken all of the time and checking them for straightness and cracks is standard operating procedure during a rebuild as is inspecting block main bearing bores and checking connecting rods for twist, bend, and big ends out of round. But we have already been there. FWIW I am gaining confidence in your machinist.
TOH
While that information might not be in any of those books, it's "Engine Rebuilding 101".
There's probably a book by that title out there somewhere!
GOOD to hear you are having the crank professionally checked,
HOPE you are doing the same with the block and conn rods, as well!
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