1963, 300 hp

[Mike S.]

Did the 300 hp 327 have flat top pistons or domed pistons? What did GM do to increase the hp of the base 250 to get the 300 hp. Thanks, Mike

[Harry S.]

Re: 1963, 300 hp

Did the 300 hp 327 have flat top pistons or domed pistons? What did GM do to increase the hp of the base 250 to get the 300 hp. Thanks, Mike

Different Carb, heads and headers to start with.

[Mike S.]

Re: 1963, 300 hp

I know the carb, cafter AFB and the heads I have were for a 300 or 340 hp, but the tach denotes it was a 300 hp

[Harry S.]

Re: 1963, 300 hp

I know the carb, cafter AFB and the heads I have were for a 300 or 340 hp, but the tach denotes it was a 300 hp

The 250hp tach and the 300hp tach were the same as I recall. The headers went from 2 inch to 2.5 inch.

[Mike S.]

Re: 1963, 300 hp

Harry, my exhaust manifold is 2.5" so am guessing it would have had 2.5" headers. The car was sold to me as a 340 hp, but with a little education, I found the car had a tach corresponding with a 250 and 300 hp engine. I am in the process of rebuilding as a 300 because of carb and heads.

[Harry S.]

Re: 1963, 300 hp

Harry, my exhaust manifold is 2.5" so am guessing it would have had 2.5" headers. The car was sold to me as a 340 hp, but with a little education, I found the car had a tach corresponding with a 250 and 300 hp engine. I am in the process of rebuilding as a 300 because of carb and heads.

Mike, what is on the stamp pad? That will tell you exactly what it was born as if it's the original block and not restamped.

[Mike S.]

Re: 1963, 300 hp

The block is incorrect, I think it came out of a 63 car or lt pickup as the casting date was F2063, it had aluminum intake with correct casting and the heads are correct casting, I am just trying to make it as correct as possible. The only records available from NCRS was the build date of July 23, 1963 and del to City Auto Sales in Chicago. Dont believe they are still in business as Ive tried locating them thru google.

[Norris W.]

Re: 1963, 300 hp

I'm not sure your question has been fully answered. 300 horse had flat top pistons with 4 valve reliefs. The heads were different from 250 horse as were the carb and exhaust manifolds. The 340 had the 11:1 domed pistons, a solid lifter camshaft (097, same as previous year's SHP 283's), same heads as 300 horse and same exhaust manifolds. 340 was alum. intake.

[Timothy B.]

Re: 1963, 300 hp

Mike,

The 300hp engine is different than the 250hp in these respects, #461 double hump heads, 2.5" exhaust manifolds, different cast iron intake #349, AFB Carter carburetor #3461.

The two engines share the same flat top pistions, camshaft and wide ratio transmission. The 340hp engine is factory built with a close ratio transmission so check this if the tranny is original, things get changed over the years.

[Mike S.]

Re: 1963, 300 hp

Norris and Tim thanks much for your help and buy the way the transmission main case was out of a 68, tailshaft housing was correct, rear end is a 3:36 ratio. Mike

[Patrick B.]

Re: 1963, 300 hp

Mike: If your block's casting date is F2063, you have a passenger car block cast in Tonawanda not Flint where all the 63 Corvette blocks were cast. A Flint block cast on June 20, 1963 would have a cast date of F203. They did not use the 6 at Flint. Also, I believe the casting number ending in 870 used a smaller font on Tonawanda blocks versus Flint blocks. There may be other subtle differences. This block is no good for judging, and I would not spend a lot of money on it for use as a driver either.