I have a late 50's International 340 that loses oil pressure to the point of rod knock when it warms up. I pulled the pan to have a peek and discovered the rod bearings and the crank to be in very good shape. I measured the rod journals and found them to be a few thousandths under, but smooth as silk and very shiny. IH makes a .002 undersize bearing for this beast, but they are hard to find and cost around $20 EACH. Since this is a low rpm (2000 MAX) motor, I would like to shim these bearings instead of replacing them. What are your thoughts? Can I simply plastigauge them and shim accordingly to get the right oil clearance? Should I take a bit off of the ends to compensate for the smaller ID? Should I give in and buy the correct bearings?

I know the correct answer is split the tractor and do a complete rebuild, but that's not a viable option at this time. I need cheap, quick, and, hopefully, effective. Share your thoughts, experiences, knowledge, etc. I'm open to suggestions.

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1986 SE 350 V8

I am wondering if it would even be possible to shim, and maintain a circle?
seems to me, a shim would create an oval/egg shape

How are you planning on shimming ? If you want to put a shim between the bearing and the block or rod you won't really fix the problem, and you will probably spin a bearin in very short order. The bearings transfer heat to the block/ rod and with a shim this would become less efficient. Put in the oversize bearing as this is the correct method. Also you may want to replace the oil pump as this may increase the volume of oil and help out with excessive clearence.

[This message has been edited by Fiero STS (edited 11-02-2009).]

I would cut a shim to fit perfectly under the bearing. They have deep tangs to prevent them from spinning. I rebuilt the oil pump a few months ago (had a warped cover), but that didn't help. I have outstanding pressure when cold, and only need to shim a couple of thousandths. Old timers have done this successfully for years and I'm hoping to carry on the tradition. I did find a complete set of .010 under bearings on ebay for $40 (plus $19!!!! shipping). Gonna call and see if they have the .002 undersize.

Engine rebuilding usually uses over sized bearings to take up excess clearances. The crank would have to be turned to the correct specs for a bearing.

TopNotch bought an 88 Duke in Texas and drove it back to Georgia with a rod knock. He pulled the pan, mic'ed the crank and bearings and inserted a piece of Reynolds Aluminum Foil between the insert and the rod and cap. He's driven the crap out of the car for the past 2 or 3 years, making probably nearly a dozen passes in our Run For The Hills courses. It's still his daily driver.

[This message has been edited by fierofool (edited 11-02-2009).]

quote Originally posted by fierofool: TopNotch bought an 88 Duke in Texas and drove it back to Georgia with a rod knock. He pulled the pan, mic'ed the crank and bearings and inserted a piece of Reynolds Aluminum Foil between the insert and the rod and cap. He's driven the crap out of the car for the past 2 or 3 years, making probably nearly a dozen passes in our Run For The Hills courses. It's still his daily driver.

For every success story ther are a hundred failures that you don't hear about. If it were an engine that was a dime a dozen I might give it a whirl. But the tractor parts are less abondant and much costlier. I would hate to ruin a 500 dollar block for the cost of a set of bearings.

Oh these kids nowadays.

Shimming used to be common. You can plastigage and shim them with brass shim stock. Cut the strips so that they fit perfectly. You want to shim the CAP, not the rod. No, you're not going to have a perfect circle, but you also don't want the brass taking the pounding of the compression stroke. If you can't get enough to tighten it with a .001 or .002 shim under the bearing on the cap, then you're probably looking at undersized bearings.

One of our custom cutting crews back in the sixties had an IHC bus with a 304 V8 they used for a bunkhouse. Every time they stopped at a town they would drop the pan and lay a strip of cardboard under the bearing on the cap. It was running when it got here, and it was running when it left. Probably made it all the way to Canada and back.

Next thing you know, these kids will say they don't even know how to pour babbit bearings.



John Stricker

Personally I'd go to a machine shop and get their recommendations. Chances are the bearing manufacturers make aftermarket bearings that would work and not cost $20 a rod for them.

First off, I assume you have an oil pressure gauge on it? And that an .002 undersize bearing would bring the clearance to within spec? If you say yes to both...

Have you tried just upgrading to VERY heavy multi-viscosity oil? I don't know if your tractor uses straight (i.e. SAE 30), or multi-viscosity ( 10W-40 ). If it's just straight, try multi weight, like 20W-50, it doesn't thin out as much when it warms up. Every other clearance in that motor is probably oversize, too, so I would'nt worry about it being too thick.

I used that method in my '90 Olds wagon, starting at about 250,000 miles. It went to 336,000 before dying from other causes.

Straight 50 weight keeps the pressure up, but the knock is still present. STP helped the pressure a little more, but did nothing for the knock. Going to plastigage the rods tonight and see how much clearance I have.

Listen to JStricker.
And I guess you kids would have a cow if you were told you could make your own bearings from babbit stock--which was also common on Ford flatheads.
Shimming was extremely common back in the 50s and before and I've shimmed N series Ford tractors more times than I can count.
Before the days of 'precision' bearings, you could actually buy shim kits from the manufactorer..
You can't do it with much success on a high rpm engine, but with a tractor, it should be no problem, but if it takes more than one shim, do NOT fold the shim double to increase the thickness---cut 2 separate shims.
Shim each rod & cap separately, tightening the cap bolts down and checking that they are not too tight.
Keep in mind, that even tho the crank journal is smooth and appears to be evenly worn, it doesn't mean the bearing mate surface isn't egg shaped.

You also need to check your mains--a worn main bearing will bleed off a lot of pressure.

Tin foil?? I have a hard time believing that---------too soft--but then again, I've heard old timers talk of using leather instaed of babbit on very low rpm engines----waaay before my time tho.

Yeah, he said he used tin foil. I wouldn't recommend it, and I wouldn't do it on my engine. Even though the tractor engine is a low rpm engine, it's a high torque engine and that puts extreme stress on the crank journals.

I do remember my father using leather in some of the farm equipment, but I don't remember what it was--tractor motor or one of the small motors that ran some of the other equipment. Today, the young folks wouldn't believe that it would ever work. Heck, my Dad even had an old Hudson that had a cork clutch.