Cub engine rebuild

[gary magee]

I am doing a complete rebuild of my 1962 cub engine. I can regrind the crank but the rest of the internal parts are beyond use. I will need to rebore but am not sure yet mow much. I am wondering about using the high compression pistons to gain the hp up to 18 from 10. Am wondering about about both avaliability and advisability of doing this vs just staying with the regular pistons? Gary

 

[teddy52food]

Find out and get oversized pistons before you bore it. Mike the cylinders just below the ridge as that is where they are wore the most.

 

[Daniel H.]

You' re really not going to gain much with just the pistons. The later engines had different cams, carburetors, manifolds and possibly a different head. Also, you may have to grind the head to allow room for the domes on the pistons to clear, especially if the head or block needs surfacing. If you add the pistons, lay the head on, with the gasket, and a couple of loose bolts to keep it from falling off, and roll the motor over to see if the head bumps up, or if you hear any interference. I suggest painting the tops of the pistons with Prussian blue to see if the is any interference. A couple of other points: use IH head bolts, available from Case/New Holland dealers as the short ones are an odd length and the closest standard length will stick down into the ports, use sealer on the head bolt threads since some of them enter the water jacket and, and that the rear main seal will not fit the retainer properly and will need to be glued in or the retainer machined for a slightly larger OD seal installed. The correct seal is no longer available and the replacement is a little smaller and prone to leak. You might want to research this further on farmallcub.com

 

[r4etired]

Remember you do not have a water pump.You might have some cooling problems with increased hp

 

[mkirsch]

If your idea of 10HP is based on the tractor's performance before the rebuild, you're in for a surprise. A badly worn engine won't be putting out anywhere near its rated HP. You'll be lucky if it had 5HP.

Domed pistons alone won't get you 18HP. The biggest contributor to the higher HP is the higher RPM that the last engines were running at. A good rebuild and breakin will get you about 12HP.

 

[El Toro]

Your local auto machine shop can measure the block
and determine how much to bore it oversize. They can probably get the os pistons and rings too.
Have them to do the valves too. Hal

 

[gary magee]

I want to thank those that responded for pointing out the many flaws in my overly simlistic idea for adding more power for what looked to be hardly any difference in cost. I'll just leave it at original but oversize specs. Thanks, Gary

 

[gary magee]

Thanks for the info. I'll stay fith the original specs in oversize! Gary