My daughter and I are still working on the 1950 JD A and are working on the pistons and rods. I noticed there wasn't any connecting rod bearings and just used shims. Do they make connecting rod bearings or do I just used "trial and error" with the shims until I get the correct clearance and torque?
- Thread starter Devon B
- Start date
susandiane
Member
You've got babbit bearnings which are adjusted by removing/adding shims. If the rods are within or close to specs after adjusting, I'd not worry about it. Actually, if nothing's kocking I'd get it as close as you can
and forgetaboutit. If you've going to work the tractor that's different--and expensive. Things can be returned to factory specs but the crank has to be welded up and ground down and the rods rebabitted and sized to
the crank. The mains might need it too. Babbit during WW2 and Korea was of lower quality as it had more lead and less tin in the alloy. I'm not sure if the quality was reduced during the Police Action but it sure
was in WWII. Korea fired up in 6/50.
Anyone know about that?
and forgetaboutit. If you've going to work the tractor that's different--and expensive. Things can be returned to factory specs but the crank has to be welded up and ground down and the rods rebabitted and sized to
the crank. The mains might need it too. Babbit during WW2 and Korea was of lower quality as it had more lead and less tin in the alloy. I'm not sure if the quality was reduced during the Police Action but it sure
was in WWII. Korea fired up in 6/50.
Anyone know about that?
Mike(NEOhio)
Well-known Member
- Location
- Newbury, Ohio
I have the rods out of my 51 and there was almost no wear in the babbitt and maybe .0005 on the journals. Haven't gotten into the mains yet. You
should adjust to .002-.003 clearance in the rod bearings.
should adjust to .002-.003 clearance in the rod bearings.
Loosehandle
Well-known Member
- Location
- Wisconsin
Plastagauge
John Deere D
Well-known Member
The most common way to measure bearing clearances is using a product called Plastigauge. Plastigauge is a thin waxy string used for measuring engine bearing clearances. The concept is so simple, yet critical, you'll never build another engine without it.
The thin wax string is placed between the journal and bearing, and then the bearing cap is torqued to specification. The Plastigauge flattens out to the exact distance between the two surfaces. The flattened wax is then measured using the supplied ruler.
Using Plastigauge is a cheap and easy way to check main and rod bearing journal clearances, and can save you the heartache inflicted by spinning or overheating a bearing because of insufficient clearance. Follow along as we show you the simple process.
The thin wax string is placed between the journal and bearing, and then the bearing cap is torqued to specification. The Plastigauge flattens out to the exact distance between the two surfaces. The flattened wax is then measured using the supplied ruler.
Using Plastigauge is a cheap and easy way to check main and rod bearing journal clearances, and can save you the heartache inflicted by spinning or overheating a bearing because of insufficient clearance. Follow along as we show you the simple process.
Mike(NEOhio)
Well-known Member
- Location
- Newbury, Ohio
Just an FYI if you go with Plastigauge. I had a hard time getting the cap on the rod without the strip falling out. I tried a dab of grease to hold
it in place and that sorta worked on one. Easy on a conventional engine with the caps coming off from the bottom. Another way is to put a small
piece o, .002 feeler gauge in and tighten the nuts. If it won't move you're OK. I ended up taking the pistons and rods out. I miced the crank in the block and measured the rods on the bench.
it in place and that sorta worked on one. Easy on a conventional engine with the caps coming off from the bottom. Another way is to put a small
piece o, .002 feeler gauge in and tighten the nuts. If it won't move you're OK. I ended up taking the pistons and rods out. I miced the crank in the block and measured the rods on the bench.
If it was running when you got it, it is probably close. If you have the piston and rod assembly out of the tractor I would mic the rod and the crank. If you can find someone with a bore gauge, I mic the crank and then zero the bore gauge to the mic and gauge the rod, the gauge reads the oil clearance. I have seen it done by eye and ear, if when assembled if you can see visual movement between the rod and crank or it has a slight knock when running remove cap and remove a shim leaf from each side, reinstall cap and if the crank rolls over good remove another leaf. Remove Leafs until the crank doesn't roll smoothly, at that point add a shim leaf to each side and you are good to go. I believe that the original operator manual discussed this method, keep in mind I am older than dirt and the memory wasn't always the best to start with.
HFP
Member
In my experience plastigage is pretty tough to use reliably on those babbit bearings, especially if there is any wear. Hopefully when you took it
apart you kept all the shim packs where they were. The thin shims in the stack are 0.003 inches. If you want to check clearance pull one 0.003
shim from each side of the rod cap and then torque the cap on the crank. It should be snug, if it is add the 0.003 shims back in and you are
done with 0.003 clearance (or pretty close). If it is still pretty loose after removing one set, repeat the process again. This is how the shim
packs were designed to be used.
apart you kept all the shim packs where they were. The thin shims in the stack are 0.003 inches. If you want to check clearance pull one 0.003
shim from each side of the rod cap and then torque the cap on the crank. It should be snug, if it is add the 0.003 shims back in and you are
done with 0.003 clearance (or pretty close). If it is still pretty loose after removing one set, repeat the process again. This is how the shim
packs were designed to be used.
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