Engine rebuild help

[Warren]

I am trying to rebuild my grandfathers 48 Cub. It had a cracked front bolster so I removed the front end and have the new part. I then did a compression test and found very low dry and wet numbers. I do not feel confident to do the valve, piston work. I can bring the engine to someplace or someone that has done this work on this unit before. The machine is in SW Michigan. Any ideas?

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[inairam]

I have used the Engine Rebuilder Association to find local shops https://www.aera.org/member-locator.html

[Glen]

Hi,
Before removing the engine from the Cub, I would check the valve clearances.
The valve clearance between the valve lifters and end of the valve stems is manually adjusted.
If nobody adjusts them, the clearance can get too small. There's a small chance that some of the valves could be not closing fully, that would make the compression lower.
The valve clearance is .013", you need a flat feeler gauge to check them.
Be sure the valve lifters are fully down before checking the clearance.
Also be sure all the valves move up and down, and aren't stuck open.
All the valves cannot be closed at the same time, you have to turn the engine to make the valves close.
The hand crank is handy for that, if you have one, if you don't have one, try using the front pulley to turn the engine.
It looks like in your picture you have the manifold off the engine, it is easy to remove the valve cover and check the valve clearances with the manifold off.

Below is a page from the 1949 Cub operator's manual telling how to set the valves.
https://farmallcub.com/rudi_cub/www.cle ... age-39.jpg

If you are going to remove the engine for rebuilding, and valve work, you could check the clearance after that too.
If you checked the compression using the hand crank it probably will be less than using the starter.
They have said on here to use the starter for doing a compression test.
Fully charge the battery before doing the test.
Open the throttle fully before doing the test, if the manifold and carburetor are on the engine when doing the test.

[ricky racer]

Welcome to the greatest Cub website on the planet!!

Before you tear into the engine, I'd suggest you check for stuck valves and verifying that it's not leaking past the valves. With the wet test you should have seen the numbers go up if it's loosing compression past the rings. If it's leaking past the valves adding oil to the bores won't change the compression numbers at all. What were your readings?

Edit: You don't need to adjust the valves at this time, you just need to verify that none of the valves are being held open by being out of adjustment. As you rotate the engine, watch the cam lobes for each valve. When the lobes are facing away from each valve, you should be able to slip a feeler gauge between the valve stem and the cam lobe. That will verify that the cam isn't holding the valve open at the wrong time,

[52DAVE]

The guy that rebuilt my 52 motor last fall is in Allendale Mi. and has been a IH. mechanic for 20+ yrs send me a pm if you want his info.

[Eugene]

Local small engine shop should be able to handle the rebuild. Also, previous IH dealership.

Reason. Small cylinder diameter.

Have a local technical college. They have a variety of mechanic's type courses. They do take projects.

[ricky racer]

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