Farmall F-20 Rod Bearing Installation

Hi guys,

I just got in the new/used set of rod bearings that I need to fix the F-20 I recently got. I have done rod bearings before, but the thing with this tractor is there is rust on the crank since two sets were removed when they spun.

Question 1, whats a good way to clean the crank/get it nice and shiny again so I can install the new bearings? I think someone mentioned Emery cloth would work to get rust off without scratching the crank? I just can remember if that's the right name of it.

Question 2, what are the torque specs for the rod bearings?

Also what is the measurement for plastiguage (i think that's what its called)? I've never used it before when putting in rod bearings and haven't had any problems, but since bearings for this tractor are hard to come by I just want to double check. If anyone can explain how to best use it/what size to get too that would be great.

Any other advice/things to look for and check are always greatly appreciated

Thanks,

~FarmallCT

A really fine emery cloth, 320 grit or finer should work well to clean up the crank. Using plasti gauge may give you mixed results without first using a micrometer to determine if journal is out of round. Being out of round from spinning bearing not the end of the world on these motors. Adjust the rod bearing with the shims until you can get slight sideways movement at the tightest spot during rotation. I recommend doing one bearing at a time and continue checking for full engine rotation as you work to catch tight spots. Check the dipper troughs in the pan for pin holes that may be letting oil drip out of pan or possibly plugged oil nozzles that fill the troughs for cause of spun bearing failure. Good luck, Mike

if the crank has rust on it you need to get that taken care of first. and if your talking about brgs. turning on the journal then it will need to be sent to a machine shop for repair. all depends on the journal condition. but just a bit of rust should be ok to remove with about a 600 grit emery cloth. you have to polish in direction of rotation, not scratch across the journal.cranks are polished and you will never get this back by hand.you can finish it off with a finer grit like 800 or 1000. i dont think these old engines are too picky and run slow. as using emery ... you are scratching the crank. and these old engines dont have much oil pressure to suspend the crank in oil. as normally the crank is suspeneded in oil when running and does not touch the brg. should be ok with a rod clearance of .004 as your talking used stuff. as in an auto engine the clearance would be .0015. and .004 would be classed worn out. i also believe that engine uses shims for clearance adjust ment. as the W30 does and this is the same engine. you would need the green plastigage as that one is for those clearances. there is red and blue also. as for the torque i think its like 70-75 lbs. but remember you have cotter pins to line up with the holes. go to the nearest hole. in the 1920's and 30's i dont think torque was crutial.you need to lay the plastige in the bottom of cap then install and torque to spec. remove cap and measure clearance with the guage provided. many times i will use 3 pieces and put one each side also. as with used stuff things are not round anymore. put together lots of used stuff and know what will work and what wont work. and never had an engine fly apart yet. its not like building a racing engine. you need to start from snug then remove shims as required till your happy.

Thanks! I will get that when I go to the auto store. I don't have a micrometer and usually don't use one, but I might look into it.

I will be sure to check and clean all the lines and dipper troughs while I'm at it.

Do you happen to know what the torque specs would be for the F-20 Rod Bearings? I found on an old post a guy who did them to 45-50 ft lbs and .003-.005 clearance but he was not going off the book.

Thanks for all the advice,

~FarmallCT

ooh, and many times i will mix and match the castle nut to the torque. meaning remove and swap out with other till the holes line up to the torgue applied. you dont need fancy tools for these engines as the plastigage gives you a good idea of whats going on. a digital caliper is ok and easy to read.

(quoted from post at 08:46:01 10/23/16) Hi guys,

I just got in the new/used set of rod bearings that I need to fix the F-20 I recently got. I have done rod bearings before, but the thing with this tractor is there is rust on the crank since two sets were removed when they spun.

Question 1, whats a good way to clean the crank/get it nice and shiny again so I can install the new bearings? I think someone mentioned Emery cloth would work to get rust off without scratching the crank? I just can remember if that's the right name of it.

Question 2, what are the torque specs for the rod bearings?

Also what is the measurement for plastiguage (i think that's what its called)? I've never used it before when putting in rod bearings and haven't had any problems, but since bearings for this tractor are hard to come by I just want to double check. If anyone can explain how to best use it/what size to get too that would be great.

Any other advice/things to look for and check are always greatly appreciated

Thanks,

~FarmallCT

Click to expand...

To clean the crank you can use a wire wheel on a drill or grinder to clean off the surface rust and a file to smooth any high spots followed up by some 320 emery cloth. You do not have to get the crank journals "shiny" down to bright steel, there will be some dark discoloration from the oxidizing "rust" and will not hurt a bit. As long as the journals are clean and smooth. Rust pits won't hurt a bit!

Setting the rod bearing clearance is a little more involved. I never use plastigauge when setting them because you are dealing with a worn crank and often used and worn bearings and the plastigauge will give an erroneous reading. IE it it will show the correct clearance in one position of the rod but when the crank is rotated the clearance could lessen and the crank lock up. The procedure I follow and with which I have had %100 success with after rebuilding a half-dozen of these engines is as follows. You basically have to put shims on each side of the rod, install on the crank, install the cap and tighten down the nuts and if the crank will not turn, the bearing is too tight. Through the process of trial and error you will have to determine that with X number of shims on each side of the rod cap and the nuts tightened, the bearing is too tight and the rod will not move.

IMPORTANT NOTE: With each test, rotate the crankshaft a FULL turn, the bearing may be loose at one point but get tight a half-turn later due to the worn nature of the bearings and crankshaft.

BUT with X+1 shim on each side the crank will rotate a full turn without that rod bearing dragging. Check each rod on the crankshaft individually and separately from the other 3 and lay each one aside with the appropriate number of shims once completed. Once all 4 rod bearing clearances are set, then install all the rods & pistons in the engine.

There are no factory torque specs for the rod bearing caps but I generally torque to 60 ft/lbs and then whatever little bit more is needed to get the cotter pin hole to line up.

Thanks!! I just got some of the black 400 and 800 sand paper, which is really fine and feels exactly like emery cloth. The only reason I didn't get any emery cloth is NAPA
didn't have the right size strips, but this felt almost exactly like it and was told it should work just as well if I'm careful. I started using it and have a little oil on the
crank where it's rusty and its coming off pretty easily with the 400 and the oil. Trying not to scratch it more than I have to but want to get everything off so the bearings
have a clean surface to go on.

I did buy some plastiguage today and was debating using it but have it just in case. It seems like everyone has a different way to go about it, but I am going to try to do just
as you mentioned with the shims until I find a number that work best.

As far as the torque that does sound about right from what I've heard, and from what I did on the last tractor I did an engine on which was a F-12.

I was hoping to keep the engine together for this but after today looks like I have to make room in the garage to take it apart (I accidentally pushed the #3 piston up too far
while trying to rotate the crankshaft to clean it through the access port, and I believe the top ring came out in the head so I can't get it back down) so this might turn into a
winter project rather than just replacing the bearings, hope to keep it in it's work clothes though. As soon as I get the new brake cylinder and lugs for my 38' Chevy it will go
outside and this will come in.

Thank you again for the advice, I greatly appreciate it!

~FarmallCT

I would make sure that once you are done, you clean, clean, clean, to get any of that grit out of there. I always oil the rod bearings when adjusting shim type bearings, I just hate to be turning a dry crank inside a dry bearing. Some people may not when adjusting a shim type bearing, bit I do. Obviously an insert bearing gets assy lube of some sort as well.