General Question about Rod Bearings/Shims/Torque

Hi Everyone,

As some of you may remember from posts awhile back, I have a 1938 Farmall F-20 I bought that spun the rod bearings. Over the past few weeks I have been cleaning up the crankshaft and working on properly shimming the rod caps. The crankshaft is clean now and has been properly sanded and is smooth. I got all the shims to where I think is about right, and this last time going through checking I did plastiguage it to make sure they are at least somewhat near the proper clearance. If I remember correctly 3 of them are around .005-.006 and one is around .004 which I think is pretty good.

My problem right now is when I torque down the nuts, I get them to about 45-50 lbs (according to a post from a few years ago is what most here people go by for torque) and some of the holes to put the cotter pins through don't line up.

In the past I was always told just tighten it to the next time the hole lines up which usually works without increasing torque too much. For some reason in that little amount of space to line it up, I am going from 45-50 lbs to 60-70ish pounds, if not a little more. This, to me, seems way too high of a torque to comfortably leave it at, especially since the original problem was spun bearings, and the cause of which is still unknown.

My question is pretty much what do I do in this situation? Is it okay for the torque to be that much higher as long as I still have the clearance between the bearings and the crankshaft?
Right now I can move 3 of them back and forth just fine on the crankshaft so I know there is enough space that they are still moving freely. The only one that I cant shift forward/back a little is #4 which was the worst one when it spun and it has a clearance of .006 ish on the plastiguage. I can still turn the engine over by had just fine with them all torqued down.

So what would you guys do/have you done on these older tractors in this situation? And is it okay that they shift back and forth easily or that the #4 doesn't but still turns fine? (I would assume its fine since it means they aren't too tight on the crank and they aren't too loose). My apologies for the long winded explanation and questions, just trying to figure out everything I need to get this wrapped up without having to tear into it again due to not torquing it right.

Thanks in advance,

FarmallCT

I believe on those you don't use cotter pins, they had a wire ran through in such a manner that the wire kept them from backing out. one wire on each rod cap

I can't confirm or deny that. I know on the letter series I have often seen wire used, though the two rods that still had caps on when I got them had cotter pins, and the same was the case with my 1937 F-12 when I rebuilt the engine in that. Not sure how much it matters, though maybe someone else will know or have some sort of reasoning for one vs the other.

Either way, I still need to get the holes to line up enough to put the wire or cotter pins through.

you can always remove some of the material on the backside of your nut so you can tighten the nut to proper torque and insert the cotter key. Most shimmed bearing like that you remove shims until the bearing is tight, then install 1 for proper clearance.

First I'd use a common bolt torque chart and look up the size of bolt you are working with and see how the torque specs. match up. When I feel like it takes too much to get to the next cotter pin hole I first try switch a few of the nuts around. Then if still not comfy with it I turn some off the back side of the nut in the lathe.

I would use a combination or compromise between the two solutions already mentioned. See what torque the bolts will take and if needed remove a bit off the nut or better yet use a washer if it will fit.

One quick way. If the nuts have washers underneath them, try swapping some around. Or as someone else suggested, swap the nuts. You'll be surprised how often that makes a difference.
And if you use lock wire, make sure you twist it tight so it can't move around and fret itself to become worn or loose.
All the best with it.
Rx

Thanks! I actually just remembered I have pretty much all the internal parts for another complete F-20 engine and I think I have all the nuts so between all those I should be able to make something work. Sounds good, thanks for the advice!

FarmallCT

That makes sense. Since I have another set of nuts I can try using those and see if they make any difference. As far as shims go I think pistons #1-4 is 10, 12, 12, and 14 shims on each side and that is about proper clearance from what the measurements say

Follow Marks advice. Do not over torque.
There are several ways to obtain the correct torque.

I am not familiar with the characteristics of that particular engine, but .005" to .006" sounds a bit too loose to me. Most modern engines require no more than .003" for rod bearing clearance. Since this is an older engine, they may tolerate such a large clearance, but I suspect that working it hard under a load might make it get a lot looser in a big hurry with that much clearance.
I may be wrong on this, but it just seems BIG to me.

How do the journals mike out? If they are egg shaped you may need that much clearance on the worn side to clear the high side.

You're making this too hard. There are no torque specs for the F series, nobody had torque wrenches. Turn the nut tighter and put the cotter pin in. They were not wired from the factory they had cotters. There are also no spec for clearance on these babbit bearings. The IH book recommends (as suggested by another reply) to remove a pair of shims until they feel tight and then put one pair back in. Did it actually spin the bearing shell or just ruin the babbit? The heavy bearing keepers the shims are between should make it impossible to "spin" the shells. It is more likely you have a plugged up port on the oil bar, the one that fills the dipper tray for the ruined bearing. Neighbor guy has a freshly overhauled 20 block in his shed on a pallet, has a nice big hole in the block where his rod came through because the oil port for #2 was plugged with a piece of crud missed in the cleaning process

Thanks, that makes a lot more sense since everyone I've talked to seems to have a different opinion on torque specs and I went on the most common ones I heard. Just trying to get it as
close to "right" as I can so I don't have any more problems with it in the near future.

You are correct, it just ruined the babbit, it didn't actually spin the shells. #3 and #4 were the worst and almost completely destroyed. #1 was fine except for a tiny grove down the
middle on both halfs and a little material build up. #2 just had a rough bearing surface. I replaced all 4 sets so I know they are all good now.

That's the one things the previous owner suggested, and it makes the most sense since #3 and #4 are farthest from where the oil bar feed comes in. Is there a easy way to take it out to
clean it or clean it in place? I was thinking blow air through each hole while plugging the rest to make sure they are all clear, though I don't want to cut any corners on this so if there
is a better way to clean it I'd be open to suggestions. I know I will be towing it and making sure everything is getting oil before trying to start it to be safe.

I did manage to get all the holes to line up for the pins by switching around the nuts and all the torques are around 50-60lbs. The head is now back on and will be torqued at 90lbs. I have
2 of the 4 pinned in and doing a final check and finishing the other 2 later today.

The only other question I have is I am slightly worried about the #4 rod, as it was the worst one to spin and needed a bit of work on the crank. All the others (#1-3) I can wiggle back and
forth very easily. #4 however, it still turns easily on the crank and I can't feel it dragging any as the engine turns smoothly and easily, but I can't wiggle it back and forth (front to
back) like the rest. Is this going to be a problem? I did get it to wiggle after turning the crank over for a few minutes, though then I took the cap off to do a final check before putting
the pins in and now it won't wiggle again. Not sure if it just needs to break in or if it's too tight or something so any advice on that is appreciated.

Thanks for all the help and advice, it really is greatly appreciated.

FarmallCT

Tighten them up and put the cotter pin in,also I don't think plastic gague was around then either.
jimmy

I would think .006 may be on the loose side, but may be ok. I make sure the cap surfaces are smooth, and no nicks, by rubbing them over a piece of sand paper glued to a piece of granite. Stan

make sure the oil trays are all filling up you may have a plugged oil nozzle. Just a few revolutions cranking should fill them up. If not your new bearings won't last long.