upon teardown of my old 73 chevy work truck (350 2-bolt),i noticed the first main bearing has pushed out of the block so far it was rubbing the back of the timing chain on the crank gear.any guesses what caused it to poke out? i didn't build this one! thank god! :rolleyes:

Incorrect assembly. There's about no other way. There's little tangs on the bearings that are supposed to hold them where they belong; sounds like maybe somebody put the bearing in backwasrds or something, such that the tang wasn't in its little slot.

Might not be a bad idea to pop the crank out and see what else they fornicated; before you discover it the hard way at some inconvenient time.

It moved but didn't spin? The oil hole no longer will supply oil to the bearing so it will weld itself to the crank. Take it the rest of the way apart I don't think you will like what you see.

thanks guys..i couldn't believe my eyes.i have the engine hanging from my homemade gantry crane in the back yard.makes a cool lawn decoration!i'll have the block inspected and use it for my stroker project.it looks better around the cam bore than the other block i was gonna use,plus its 6 years older and probably a stronger block.

It sounds like it spun a bearing to me, probably from lack of lubrication, or just geneeral abuse and lack of care over 30 years.

By the way, the bearings are NOT held in place by the little "tangs" They are there to help properly locate the bearing during assembly, but the bearing is held in place by the "crush" of the main cap or rod cap. Take a look at the cam bearings, there is no tangs on them, but they stay in place just fine.

thanks for your input,BillK.

oh yeah....267,058 miles on the odometer..i bought it used and got 10 years of daily transportation out of it for 1350.00!upon teardown i noticed it has been rebuilt at least once.the block will be a good candidate for splayed 4-bolt cap conversion.i'll have the shop check it first.