The Stovebolt Site Forums The Shop Area Engine Shop siezing cam shaft bearings

when we tighten all of the caps, the engine becomes almost imposible to turn by hand. but if the rear cap is taken off then its spins with ease. even making the rear cap "snug" with out being torqued down creates far too much resistance. and i read somewhere that that there needs to be shims? i already wasted a WHOLE day on this problem. And we are almost positve the bearings are in the right place. HELPPPP!

I'm assuming we're discussing crankshaft main bearings and that the engine in question is a '54 235 mentioned on another post (?)

The shop manual shows the ammeter method or you can use plastigage and check for .001" to .003" clearance for new bearings, .001" to .0045" for used bearings.
Hope this helps.

What process have you used on the other main bearings and what year is the engine?

Don't forget the rear main holds the rear main seal, and a brand new one is going to create some extra resistance until it squishes a bit.

Stuart

you didn't waste a whole day as perhaps you are learning something.
what are the bearings clearancing at and the rear should be checked without the seal installed
ron

wow i totally forgot about the rear main seal. and i just found out that my dad broke the rear cap while trying to figure it out. the plastigauge was fine on all the bearings so we skipped that process on the rear. stupid me.

If you are saying that the rear cap was replaced, you might have a problem. It might not fit properly.

if you broke the rear cap, you need to replace the cap, then get the crank bore align honed. No ifs and or butts. There are no two caps that are the same.

Just what Scott said, don't even try looking for one that works. I did the same thing on a Pontiac a bunch of years ago, the cap broke, I grabbed the closest one I had, checked it, thought it was Ok and finished the build. It ran for about 15 seconds before locking up! A alignment hone and polished crack cure it. Joe

How is it broke? Actually a broken off peice, or is it just cracked? I've seen cracked main caps brazed up, and work just fine. In fact, #3 in my 235 was cracked, my machinist (over 50 years experience) brazed it up for me. He told me to used hardened washers under the bolt heads to help spread the load. Worked very well, although finding 9/16" hardened washers was a royal PITA.

im not sure how my dad broke it. but he became so frustrated that he just took the engine to the shop and told them to do it. but we'll get it back this weekend and finish the engine assembly. Thanks again