Heads Up

[George G. Leverette]

Would a 383 Engine with 915 closed chamber heads provide equal or better performance than 906 heads on the same engine? What are the pros and cons?

[Slingshot383]

You'll be getting a little more compression, not any better ports. As a matter of fact, 906's can be made to perform better than the 915's can.

[Stoga]

Unported, I'd probably go with th 915s, but otherwise I agree with Slingshot.
The other thing to keep in mind is 915s are getting a lil bit collectible.
There's folks restoring GTX's and RT's who'd much rather have an unported set.
Also,people who race NHRA stock class would probably appreciate a set of 915s alot more if they are unmolested.

[perfmachst]

hello, an engine is an air pump. it needs air in and air out to make power, there is a lot more gain with better flowing heads, than raising the compression ratio. the 906 does and will out flow the 915 head, especially in the .100 to .400 range, where the valve spends most of it's time. just food for thought. by the way, the 915 is legal on 67 -440. 68 up has to use the 906 head.