Thread: need help...1969 chevy 350 4 bolt main

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i have a 1969 350 chevy block i'm trying to find out how much horsepower i have i have checked the casting numbers but the last number that's supose to be on the front by the head is gone.... the casting number is 3970010 date code is G 17 8
now there's one more thing thing the piston has a code on it 3959456 what is that code mean....please help if you can thank you

39700010 was used from 68-mid seventies. Both two and four bolt. Piston no. is GM number for a cast flat top production piston.

So for sure you have a Chevy block with stock pistons. Most of these were around 275 hp. Unless the crank is steel. Then it could have been from 275 to over 300.

To tell if the crank is steel, the parting line that runs from the front to the rear of the crank will be about 3/8 ths inch wide.. If the line is just 1/16 wide or less, the crank is cast iron.

Factory hp. means nothing anyways if you are going to build this motor. It will make a good basis for just about anything up to 400 hp.