tight fitting pistons

Bob in Tennessee · Jul 2, 2015

Just got my 172 gas block back from machine shop. Installed crank,cam, flyweel, and clutch. Put on tractor then tried to install
pistons. The pistons are marked STD but they are so tight in the bores that I can't push in. Took rings off and tried every bore
upside down. Pistons drop in easy until reaching the skirt which stops entrance. Kit came from this site so I trusted it's worth.
Is my only recourse to take block to machine shop to enlarge bore? After all i've done and paid, it kind of gets me grouchy to
undo so much. Is it possible to hone out a fit this tight? Has anyone gotten sleeves too tight for the pistons?
Durn!!!

gears · Jul 2, 2015

did the shop have the pistons in hand when they bored the block? Have you mic'd the pistons and compared clearance mathematically?

It sounds to me like something is tapered.

RodinNS · Jul 2, 2015

If the machine shop didn't have the pistons then they likely didn't know what diameter to put the bores to for the final finish... so it would be up to you to do that with the hone. I would first mic the pistons as stated in the service manual and verify their OD's then mic the bores at 4 points or as stated in the manual to check their ID's and compare against spec. Then... if you determine that the bores are straight and undersize... then you hone them out.

Rod

john in la · Jul 2, 2015

Do not get upset. This site only re-sells parts.
If the parts were manufactured wrong it would not be this sites fault.

Now about your problem.
It sounds like you bought piston and sleeves.
Did you or a machine shop install the sleeves?

First you install the sleeves.
Then you fit the sleeves to the pistons using feller gauge hooked to a pull gauge.
You stick the feller gauge between the piston and the sleeve and measure how many pounds of pull it takes to pull the feller gauge out.
You hone the sleeves to you get the proper pull tension.
Once you have the bore correct
You fit the rings to the bore.
If the ring end gap is to small you file the end of the ring with a special fixture.

All of this is outlined in the Ford shop manual.
If you had the sleeves installed by a machine shop you should have took the pistons; rings; and rods; to them to have all this fitting done.

David G · Jul 2, 2015

You always want to take the pistons to the machine shop so they can bore to fit.

Bob in Tennessee · Jul 3, 2015

Machine shop installed sleeves and had pistons. Why is it that Tisco can manufacture a piston kit and not have pistons properly fit sleeves? If sleeves have to be bored to fit pistons then sleeves have to be re-honed for ring seat. All pistons are tight in all bores therefore a universal problem.

Bern · Jul 3, 2015

Any good machine shop should have caught this issue if they had the pistons in hand. I'm guessing the pistons are fine and that it's the sleeves that are the issue here. More specifically, the thin wall sleeves have distorted somewhat upon installation. Myself, I would be running a bore gauge through each and every hole to see if they are tapered and/or out-of-round. If they are, I'd pack everything up and send it back to the machine shop. It would then be their problem.

RodinNS · Jul 3, 2015

Well, from what you just said... it's not Tisco that goofed... it's the machine shop that screwed up. Take it back and have them fix it. There's no bloody excuse for that if they had all the parts.

Rod

David G · Jul 3, 2015

Filing the rings to fit leaves a little burr on the end of the rings, make sure and clean that off when done, BTDT.

Bob in Tennessee · Jul 3, 2015

Totally agree with you guys the machine shop should have caught this BUT how in the .....does Tisco ship a kit that does not fit? I've only done a dozen or two of these and this is the 1st time i've have had to have sleeves bored to fit pistons that came in a kit!!!! Very poor of the manufacturer. It wasn't a thin wall collapse, it was endemic of all sleeves. I had this block assembled on the tractor now it's in the back of my truck to go back to town. Sorry to vent! Hope you guys have a great fourth and isn't it great to live in the USA!

john in la · Jul 3, 2015

"Why is it that Tisco can manufacture a piston kit and not have pistons properly fit sleeves?"

So you are expecting Tisco to make a sleeve that is such a tight fit into the block that it has to be pressed in yet once installed if it is 0.0005 to big it is trash or 0.0005 to small the piston does not fit correctly.
We are dealing with such tight tolerances here that the pistons are even numbered. The #1 piston goes in the #1 hole. It will not work in the #2 or #3 hole only the #1.

Once again I will say....
You take everything to the machine shop or do your self.
Install the sleeves.
Hones the sleeves to fit the piston.
Files the rings to fit the new bore.
Puts the piston on the proper #'erd rod in the right orientation.
Checks the clearance of the rod bearing to the crank journal and the main bearing to the crank journal.
(To tell if the crank needs to be turned down.

Once all this is done you will have sets for each cylinder.
You tell what set goes in the #1 hole by the #1 marked on the rod.
You also do not mix up the rod caps. They will also be marked to match the rod they go with.
If everything is properly done the notch in the piston will face forward.
The rod oil squirt hole will be to the right.
and the rod numbers will be to the left.

When all the above is done make sure you understand "Piston Ring Orientation" before installing the pistons in the bore.

Bern · Jul 3, 2015

This post has really intrigued me, so I did some research in the service and parts manuals.

According to the factory repair manual, even though the block uses sleeves, pistons are to be fitted to the sleeves after they are in the block. If they're too tight, the instructions say to hone to fit. If they're too loose, a person is supposed to order oversize pistons. I just checked the parts book, which lists oversized pistons as if it were a parent bore block.

This is pretty much unheard of in today's world. When you buy pistons and sleeves, most manufacturers don't even recommend checking piston-to-bore clearance, because it will be automatically correct. Some manufacturers even go so far as to package the pistons and sleeves together and ask you to install it as a unit.

I suspect that the folks who did the machine work have the same mindset, which could be why they didn't check it.

john in la · Jul 3, 2015

Bern I have to agree with everything you said.
It should be a plug and play system but often is not.

You could look at it several ways....
If every bore and piston are the same size down to 0.0005 then why are sleeves and pistons sold in matching sets; or why do the even stamp numbers on the rods so you can put it in the correct bore.

Also lets assume the block is 0.0005 off. You stick the sleeve in the freezer to shrink it and get it in the block. When it warms back up is it going to expand to the proper size; or is it going to expand to the size the block will allow it to.

I would much rather be in the situation the original poster is in where I had to hone the sleeve so the piston will fit rather than the sleeve being to big.
I also wonder how many people have put together a motor using the plug and play concept and the sleeves were really to big.

I take the same point on rear main seals.
How often have you seen people post here that they changed the rear main seal and it still leaks. Often doing it several times over trying to get the leak to stop.
Well duh!!!! After 50 years of wear do you think the leak may have been caused because the crank is worn from the seal constantly rubbing on it.

Robert Major · Jul 4, 2015

Hi
You'd be real impressed with the visit to the Basildon, Ford tractor factory I went on in the U.K in 1991, for an Agricultural engineering course trip.
We toured the whole factory including the motor machining and assembly line. The guide was explaining the machining tolerance. Every piston/ bore in a block was assigned a letter from the dimensions right off the boring machine.

The pistons/rods then went in a basket in order to fit the block on the assembly line. we watched the process for a 6 cyl. every single piston and bore was a different size. we watched our guide pick up pistons show us and then dump them back in the wrong slots. That motor either failed inspection or went out wrong. In 1991 if Ford couldn't get pistons and bores all the same do you ever wonder why made in China parts don't fit L.O.L.

Later in life I met up with an acquaintance of a guy picking up reject parts from ford in the U.k. They got a 6cyl tractor motor never run, right from the factory. it would turn both ways to a point then not go over compression. They pulled the head and found a tobacco tin sitting on top of a piston. i guess somebody dropped it in while the head was being put on . Their pulling tractor had a brand new never run very cheap motor!. Ford lost a great deal of money that day, I bet then that was a $7000 plus motor, ever wonder why some cheap machines from a very foreign country don't go so well with a lack of attention to detail on assembly!!!!!..

David G · Jul 4, 2015

I bought a piston sleeve set a while back, and the machine shop guy told me that they find inconsistencies, so always check fit. As an engineer, this surprises me that they are not plug and play.

Bern · Jul 4, 2015

They weren't plug and play back in the 50's. The factory repair manual specifically states that piston-to-bore clearance must be checked and adjusted if necessary.

David G · Jul 4, 2015

I would not expect it then, but now with computer controlled equipment it should be.

Bern · Jul 4, 2015

I would agree with you about today's machining capabilities. However, maybe the 3rd world manufacturer of the parts has the same mindset of those in the 1950s. Or at least, uses the factory recommendations as an out for parts that are not machined to tolerance.

Bob in Tennessee · Jul 4, 2015

Thank you John for taking the time to respond. Thanks you also for outlining process. I have done many engines over the years and I know the drill. Mopar, Chevy, and of course, Antique Fords. Sleeved engines, non-sleeved, dry sleeved, wet sleeved ect. All engines i've ever done had to have some attention shown to each cylinder, and ring before assembly, But in your defense of Tisco you are missing the point. The pistons do not come close to fitting the sleeves. They have to be shoved in with effort. It's more than a simple hone. Modern technology should allow an easier assembly. Perhaps not "plug and play", but certainly not machine shop cylinder bore. Best wishes to all responders and thanks for the insight.

Monday morning it's off to the machine shop and hopefully no problems getting the sleeves fitted. Looking forward to working this 841 instead of it working me.

Bern · Jul 4, 2015

I've seen many Ford blocks that have an A,B,C, or D painted on the side of the block for each bore. Same thing for many pistons, these are typically stamped in the crown. Most of the time, you'll see a B or C (middle of the range). I think the idea at the time was to match an "A" bore with an "A" piston, "B" with "B", etc.

Whenever I rebuild a Ford using new pistons, I always mic my pistons and bores. I mix and match as needed to get large pistons in large holes, and small pistons in small holes. The difference between "large" and "small" could be as little as .0005" (1/2 of a thousandth of an inch).

This is especially critical with a 401 6-cylinder, as the #6 hole needs a bit more running clearance than the rest. I'll purposely put the largest diameter piston closest to the front, and smallest in the back on those engines. If clearance is too tight, back to the machine shop it goes!

greg gg · Jul 4, 2015

Similar issue with piston sleeve rebuild kit for a 134 red tiger. After pressing sleeves in, the pistons felt tight. Too tight to pull feeler gage. I didn't want to hone (new sleeves had a nice finish and measered concentric and true). Old pistons measured .001 smaller and ring lands in good shape so I used them. Two years of plowing, discing and bush hogging at hunting camp and still runs like new.

john in la · Jul 4, 2015

Thanks Bob.
Yes I'm thinking running a hone threw the bore should clean it up.
My bad.
If the sleeves need "boring" then that is a different animal.
I guess I just assumed you dry fitted the pistons to the sleeves before having the sleeves installed to make sure you had correct parts.

Before I went to "boring" I would give YT parts a call and ask for their advise.

It would be interesting to know if the pistons or the sleeves are to blame.

George by Geneva, NY · Jul 5, 2015

Take block and pistons to a engine shop that knows how and what to do. Even IT manual says have to hone new sleeves. Any press in / tight fit part one would expect to have to do the final sizing after installation. All the dry sleeves I ever saw installed had to be bored to fit piston after installed.

Bob in Tennessee · Jul 6, 2015

Well I took the block back to machine shop and owner acted dumbfounded like he had never seen this. Said he would charge me 60.00 to bore sleeves. At this point I'm not concerned with who's to blame. He said he'd have to take several thousandth's off each cylinder. Boy Tisco messed this one up. Anyway i'll pay to have it right. I'll be driving to a new machine shop for my '44 2N this winter.
On a happier note, 4th of July in our piece of Tennessee went like this, our 24 yr old son came by to light fireworks so the old man could relax in a chair and watch. The little woman bought a great big-a&& rocket that was supposed to explode into all the colors of the rainbow. Son lit the fuse and rocket never left the launching pad. It exploded all right!!! I'm still hearing ringing in my ears! Don't know about the rainbow colors but when I got up off my butt, my 120 lb German Shepard had dove into my garage closet and all my stacked 841 parts came crashing down. Got the dog out, can't find the two cats, and my son has never moved that fast. Altogether a great day. Lots of rain on the pastures, fresh green beans on the table.
Bob

john in la · Jul 6, 2015

So did anyone mic the pistons.
Are the pistons to big or the sleeve to small.
Was thinking the sleeves may be right but while the pistons may be marked standard are really oversized.

tight fitting pistons

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