I have a 69 Cutlass that has had a 455 Fa motor installed with G Heads. I have been told that is a good thing. I'm just wondering what makes them better, what car were they originally on, compression ratio, etc?

Steve

 

G heads are 1971 (assuming they aren't actually GA heads from 1972 - look closely for the subscript "A"). They do have factory hardened seats, but that is just induction hardening of the cast iron, not inserts. Could be big or small valves, depending on the original application. The FA block would have been 1973-newer typically. What does the VIN derivative say for the model year?

 

The # on the block is 396021Fa, the head is just the G. Are there any other #s on the block or heads?

Steve

 

 

33M326551 is the # , does this tell the year of the block?
thanks, Steve

 

The second character is the model year. 3 = 1973. The G heads were not born on that block.

 

Final question, and once again thank you, you have helped me fix many things on my car. So I have a 73 block with 71 heads? Does the block # give any idea what model car it was out of, are the last 4 or 5 suppose to match the VIN#.

Steve

 

Actually, the first character of the VIN derivative will match the first character of the VIN, and the last eight of the VIN derivative will match the last eight of the VIN. The "M" indicates the car was built at the Lansing plant, and the last six would tend to indicate that it was an A-body (Lansing assigned sequence numbers 100001-400000) to A-body cars that year) but there are documented cars that don't match that convention. Where it actually came from is kind of irrelevant at this point. You know the motor has been apart since the heads don't match. You'd have to tear it down completely and inspect the pistons and cam to figure out what they are.