rod bearing cap loose screw

Mon Feb 10, 2014 12:36 am

I dug out my granddad's 48 cub. Been sitting since 1978 in the dry. Put oil in it, new filter, cleaned breather and a little Marvel Mystery Oil. Started with hand crank and have been using it for a year. Started knocking a month ago, so I parked until today. Pulled oil pan and found the #2 rod bearing cap loose. Had 1 different nut than rest of rods and had come homemade locking tab to keep it tight (obviously didn't last.) Journals look ok (minor scratches on #2) bearings are oddly pitted. Has standard IH bearings.

I want to replace rod bearings and the odd nut. Where do I get the nuts from? Should I/ can I replace the main bearings without removing engine? Oil pressure gets low once engine is hot.

I have some blow-by coming from crankcase but very little smoke from exhaust (only under heavy load). How much trouble to put a set of rings?

I don't have an enclosed shop and don't have a lot of time or money to spend, however I don't want to ruin the tractor.

Any advice on how far to go with this repair?
Hope I was clear.

Thanks in advance!

Re: rod bearing cap loose screw

Mon Feb 10, 2014 6:31 pm

You can install mains without taking the engine out, not a big deal. take the off the 2 outer main caps and loosen the middle cap. place a brass rivet in the oil hole in the crank journal , as you turn the crank the bearing will slide out. replace in the reverse order. replace the 2 outer caps and hand tighten the bolts. then remove the middle cap , and repeat the process, you may have to help this bearing out with the aid of a screwdriver as it is the thrust bearing. Use plenty of oil when installing the bearings. your Cae/IH dealer can supply you the nuts , Rings are not a problem to install.

Re: rod bearing cap loose screw

Mon Feb 10, 2014 6:32 pm

I would lap the valves too

Re: rod bearing cap loose screw

Mon Feb 10, 2014 9:10 pm

Rings are probably stuck in the grooves of the pistons. I've had some, so stuck, that they had to be chipped out. Don't just loosen stuck rings, replace them.

Re: rod bearing cap loose screw

Mon Feb 10, 2014 10:13 pm

My opinion, since you are planning on replacing the rod and main bearings. Do an in tractor over haul, rings, bearings, valves.

Re: rod bearing cap loose screw

Tue Feb 11, 2014 9:27 am

i don't trust the rod bearing nuts to stay put, particularly when you are only torqueing less than 20 lbs. (16 if i remember correctly) so i stake the nuts. i've taken several engines apart with rod cap problems - one Ford so loose it trashed the rod and the crank journal.

Re: rod bearing cap loose screw

Tue Feb 11, 2014 10:28 am

Congratulations on getting granddads CUB running again.

You can do a in frame rebuild on these engines easy enough, personally I would replace the rings and bearings also as described by others, you can plasti gauge all the bearings and see what size you need they make bearings for slightly worn assemblies

You can lightly hone the cylinders but make sure you put something below the cylinders to catch the grit, rags or something then make sure to rinse the cylinders really good keeping the grit out of the bottom end of the engine.

I also suggest you lap the valves its not that hard.

How low is your oil pressure getting when hot, what oil are you using?

I would use loctite on the rod and main fasteners does not hurt to stake them too.

Good luck please keep us up to date with your progress.

Re: rod bearing cap loose screw

Thu Feb 13, 2014 11:04 am

I used started with 30 wt and tried 20w50 with same problem of below 20.
I am not familiar with this engine and am an amateur at best on any engine. Regarding keeping grit out of engines, I am concerned about lapping the valves and grit in the the valve guides and running on to the cam. Without breaking the engine down, am I able to really get this stuff out of oil ports, etc..?

Thanks again.