ive got a 88 iroc vert that has a different motor in it than the original, i know all verts came with 305's but i was wondering if i could tell if it is for sure or if its a 350, i emailed the guys at summit and they said i would have to look at the numbers on the back of the motor above the bellhousing, which i dont want to do, was just wonderin if you guys knew how to tell...thanks!

 

Yes, look at the numbers on the back of the block.

Or if you don't want to do that, take the head off and measure the bore.

 

If you took the valve cover off and got the casting number off of the cyclinder heads it might help give you a clue as to what motor it is. If it has a 305 head on it, it is probably a 305.

 

416, 081 - head casting numbers typically found on a 305.

 

Those are the only 2 ways to determine the actual size of the motor. Seeing 638 or 627 stamped on the bottom of the block doesn't mean squat. Because my engine has both of those stamped on either side and it's a 305.

Head casting numbers are a good indication, but there are people who will swap out to a 350 block but keep the 305 heads. For the longest time I thought I had a 350 because of the 638 under the block because the damn thing was so quick for a 305. Then I had to remove the heads because of a bad head gasket and lo and behold, a 3.75 bore space. In a weird way I was happy that it was a 305 for 2 reasons. 1 being that it was the original block and untouched, and 2 because it was a freaky strong 305.

 

cool, it doesnt take much to take a valve cover off is it????

 

The easiest and most accurate way is to look on the back of the block. Do not trust head casting numbers since any shade tree mechanic can put 350 heads on a 305. Get a brush some engine degreaser and a mirrior... take 10 minutes and look for 5.0LG or 5.7LG then the numbers so we can look up what type of block you posess

 

how and where am i gonna find that, on the back of the block??.thanks guys

 

MorTec, Chevy V-8 Engine Block and Head Casting Number Locations

 

haha i cant tell by the way it drives or sounds no other ways huh....thats sucks im really wishin its a 350

 

that link helped..ill have to check that out tomorrow maybe thanks!!!

 

just let us know

 

Another way to tell is the size of the harmonic balancer. The 305 balancer is smaller in diameter and thicker, the 350 one is larger in diameter and a bit thinner. Of course I agree that the block casting number is the only sure fire way to know, since any schmo can put the wrong balancer on a motor too.

 

Yeah I wouldn't rely on the balancer, since mine has been upgraded and such when I had a 305.