Farmall Super C Crank question

Hi, I'm new to the forum and would appreciate any feedback. I'm rebuilding my 1953 Super C and am unsure what to do about rod bearings. I do not want to pull the crank and thus am having a hard time getting an accurate measurement on the crank....I'm seeing anywhere from 1.735-1.736 on the crank where the rods go. I have not measured the mains. This doesn't make much sense to me. I know that factory was 1.749-1.751, does this mean at some time this crank was turned down .010 and now has wore another .004"? I don't know how or why that would happen. You wouldn't normally see that much wear ?? Suggestions/Thoughts?

A crank will wear out of round. So it might be just the part of the journal you are using for the measurement. Another words if you happen to be reading on the side that is where the rod rides, when coming up on the compression stroke, and down on the power stroke it will be smaller than the other quadrant of the crankpin. This would make it appear to be woren more than it really is. Some manufactures will make .015 under bearings also. Not often

You had better pull the crank and get it ground. If the rods are wore chances are the mains are too. They should be able to go to .020 and get bearings to fit. Then it will have good oil pressure if the pump is good. Take the pump apart and make sure the plate is good.

You need to pull the crankshaft and have your local auto machine shop measure it for wear and determine how much it needs to be ground undersize. They can supply the correct undersize bearings too. If the block is sludged up you need to have it cleaned and all the oil passages cleaned too. That area where the sleeve seal is installed needs to be thoroughly cleaned so there's no coolant leakage. Hal

One thing is are you real experienced reading a Micrometer?It could be off a little and you reading it could be off a little.The best thing would be to ask a machinist or somebody what they thought.4 thousandths you can have 2 thousandths for clearance,mic off 1,you off 1 and be in tolerance.

What are you using to measure with? Being just a whisker out of square will distort your measurement if you're using a caliper. the wider anvils of a .0001 micrometer will give you better and more consistent measurements. Are you doing this in-frame from under the tractor? That might be another factor. You want to be real good with a mic to be taking measurements in a tight space like that while working upside down. Awkward positions don't lend themselves well to consistent measurements.

caterpillar guy is right on the money. You need to be measuring at two or three points on each and at least two directions. If the crank is worn down that much, you might find them out of round, too, at which point you should probably pull the motor and have the crank turned down to .020 under.

I don't know how you'd be able to get a reliable measurement on your mains without pulling the motor and crank.

Being out of square will give a bigger reading than it actually is. It may be worn more than .004. To do the job right it should be pulled.

Exactly, and agreed, on both counts.

If he is using a caliper, he could be measuring too much. Allow another .005 for that, and another one or two thousandths for the caliper slipping when it's pulled away to read it, and another .001 for the limit of the accuracy of the caliper, and it COULD turn out that he's actually measuring a perfectly good pin that's been turned to .020 under.

I've taken measurements like that early on in a project just for the purpose of sizing up what might need to be done, but the final measurements that lead to a decision are made with the crank out. As far as the crank pins, I could be comfortable with measurements taken on some cranks with the motor on a stand and upside down, so that everything is in reach and lighted well and room to move the mic, but if he thinks he's got issues with wear, then the mains need checking, too, and the only way to do that right is to pull the motor and get the crank out.

I'm a little vague (memory--the second thing to go) but I seem to recall that any crank I ever had turned, the shop stamped right into the crank somewhere either the new measurements or how much they had turned it down.

The back of the old bearing should have a part # and usually will be stamped std oe .010 if oversize

Thanks for the feedback. Pretty much everything that everyone has said...just confirms what I knew I should do (pull the crank). I am experienced with reading mics and calipers, but the biggest thing is the "trying to stand on my head getting an accurate measurement". I'm going to scrub clean a rod bearing tonight and try to find a number on it. To this point I've only found a Fm (Federal Mogul) and a 12 (which I've been told is merely the month in which it was manufactured. I also found an p/n 1795 CA which appears to be stamped using an ink. A local shop swears that if I clean it up, I will indeed find a number on it which will tell me if it is std, .010" or .020" oversized compensating for a ground crank. Thanks for input.

Yes, I used to grind cranks too & I stamped the size of them.

(quoted from post at 08:24:31 01/06/09)

......... I don't know how you'd be able to get a reliable measurement on your mains without pulling the motor and crank.

Click to expand...

By using a micrometer designed to measure main journals while installed. It is a V shaped block with the micrometer located through the angle of the V. Place the V on the shaft and run the micrometer up to touch and get a direct reading of size. Works on any size shaft that fits in the V.

this is not uncommon on a C if they missed a fit when originally grinding the crankshaft they would take .010 off all the throws and install .010 under bearings IH shows bearings off .010 and even .020 plus standard this was done at original assembly found this out when i had to replce bearings in my c 20 years sgo thanks to a son in law that ran it with it leaking oil