Does anyone know if a 74 L48 engine is a 2 or 4 bolt main?
Is there any way to tell using the casting numbers? or do i have to pull off the oil pan and look?

 

Hi '74, you'll have to drop the pan to know for sure but here is a little info from my own experience. The factory L48 in my '78 has block casting #3970010, the books all say this block was cast from 1968 thru 1976. GM installed these in everything they turned out. I've torn down three engines with the same casting number and they have all been four bolt's. I have not pulled my L48 apart so I can't say for sure but my money is on it being a four bolt.

 

Thanks Buckshot and my Engine's cast number is also3970010

 

Saw a '73 L48 that was a two-bolt. I believe from some of the old mag articles that the L48s were all two-bolt mains.

 

Check your number through www.mortec.com , should get an answer there.

 

If I remember correctly most of the 4 bolt main engines had a 1/8" pipe plug on the top of the block in front of the intake just behind the timing cover.

 

Thanx starship but it didnt really help becuase for the casting number i have (#3970010) it is listed as 2 or 4 bolt

 

Yeah... L48's were 2 bolts. But that same block was used for the LT1's in '70-72 in the 4 bolt set up... no difference in the oil galleys on that one.

 

I'm hoping to pull the factory motor out this winter and replace it with a stroker, I'll be pullin' the pan off for sure 'cause I'm curious as to what GM had left over and stuck in the late '77's. I'll let you know as soon the last pan bolt is out.

 

Would you be able to tell by the size of the harmonic balancer?