Hi guys, I'm building a 1971 Cutlass 442 clone/tribulte car. I'm in the process of building a 455 engine. My engine is a 1970 with E heads, are the 1971 G heads as good for performance? I don't want to lose performance, but I would think the engine might be more appropriate if it has the G on the heads, due to the fact the G heads were for model year 1971. I can trade the E heads for G heads, is this a fair trade? Thanks.

 

Bigger valves makes the significant difference. And, the proper letter is good.

Use the G's if possible

 

If they are the same valve size there wont be much difference in performance.

 

have been reading this thread and i am about to start Re-building a 1971 455" w/G heads. If i'm correct i have to remove the heads to measure the valves. Somewhat new to this and would like to know which part of the valve to measure. I assume its the measurement of the top of the valve. And also, was there just 2valve sizes in that year? many thanks, Charly9g.