Engine Rebuild ?'s

Regards,
TJ

Being eager to learn, I talked to as many horse trainers as I could (and read as much as I could on the subject).

I found that if I ask 10 different horse trainers the same question I would usually get 10 different answers.

A couple of years ago, I rebuilt the engine on a 1953 Jubilee project tractor. I had the head reworked (new valves, valve guides, valve springs, valve seals, etc…) After some research and reading several different points of view, I decided to have the sleeves bored out .010 rather than R&R the sleeves (the FO-19 manual stated that this is the preferred overhaul if the cylinder walls are not scared badly verses R&R the sleeves). I installed oversized pistons and rings. Had the crank ground .010 over and installed new bearings; had the rods resized and fitted to the pistons and piston bushings. I had the oil pump rebuilt. I did not replace the cam shaft, lifters, rocker arms and push rods.

My engine runs exceptionally well; lots of power, uses no oil, 60 #’s of oil pressure hot or cold, low idle or high idol. I expect it will last for many years to come.

Maybe some of the more experienced tractor engine rebuilders will chime in with their advice to help you make an informed decision.

HTH. Rick

I have absolutely no experience with NAA motors but 30+ years with similar cam in block overhead valve automobile engines. TRUE FACT: camshafts, rocker shafts, and lifters wear just like other engine components. Loss of upper end lubrication can take the whole ball of wax out as fast or faster than lower end components. That said some or all of what follows may or may not be pertinent to NAA motors.

IMHO a quality rebuild of these types of motors should include as a minimum a new (preferred) or reground cam, new lifters, and new rocker shaft bushings. The only way to really evaluate the cam is to mic ALL of the lobes and journals and inspect for signs of heating. A little challenging for a novice. New bushings cost peanuts and new cam and lifter kits are often available for a very modest price. The rocker shaft itself should be examined for wear and replaced if worn. If the pushrods have oil galleries they should be cooked along with the head and flushed with compressed air. Worn or bent pushrods should be replaced. Valve guides should be checked for excessive wear and replaced if worn. All valve seals should be replaced. The rockers themselves are usually reusable but should be thoroughly cleaned and examined for damage. Rocker pedestals and feet should be checked and replaced if excessivly worn. If the cam runs in bearings they should be replaced. Timing chains and gears might be reusable but again they are usually inexpensive and they don't last forever.

All in all - price the parts and then ask yourself what your labor and down time on the machine is worth if you have to redo some or all of the job in the next 5+ years.

TOH - a man who has tired of redoing the job later for more than the proper job would have cost to begin with.

The parts you mentioned are generally not replaced in a standard overhaul. I think those parts are pretty tough. Also, in my view and based on my personal experience, those old parts are probably of better quality (even if slightly worn) than new aftermarket parts.

Of course, this is just my subjective opinion.

HTH. Rick

Paul K.

I say if you find a source, replace it while you are in there. If not - don't sweat it, these engines are remarkably tolerant to wear and abuse.

Good luck,
Dan