383 Heads vs Compression/Power

[tadam05]

I recently purchased a slightly used 1969 383 off of my brother. He has aluminum Edelbrock heads/Speed Pro forged pistons in the engine. I am looking to put this engine in my car but would like to go with the stock 906 heads (I am putting the car back to stock). He claims final compression to be 9.6 to 1 w/aluminum. If I were to install my factory 906 cast heads will I take a big hit on the compression/power of this engine. New to this motor stuff any help is appreciated.

 

[69 Runner]

More info please. It would help if we knew the chamber cc's of both heads, and what your deck height is. If the chambers in both heads are the same size, then the compression ratio will be the same. HOWEVER....because of the different thermal properties between the steel and aluminum heads they won't react the same.

 

[tadam05]

I was told that the Edelbrock performer RPM's used, part no. 60929, have an 84 cc chamber, I am not sure what chamber cc's the 906's have. I haven't had the 906's rebuilt yet but I do know that they have never been touched, as of yet, but was planning on having them rebuilt for my project. As far as deck height, how do I determine this????Thanks.

 

[69 Runner]

Blueprint spec on a 906 is 79.5cc, but in reality they aren't close to that unless you have them cut. They may well have up to a 90cc chamber as is. Have them checked before you have any work done. Chances are you're not gonna change your compression much at all.

By the way, the difference in compression with the steel shim head gasket and (say) a Felpro blue is about 1/2 a point.

 

[tadam05]

Thanks a bunch 69 runner, when I have them rebuilt I will also have chamber cc checked as well.

 

[392hemix]

What are you doing with the old heads? i might want them for a 440 i have

 

[daredevil]

93 octane is fine at 9.5 to 1

 

[tadam05]

392hemix, The heads don' come as part of the deal to me, I beleive my brother is putting them on a stroker. if anything changes I will let you know if they are for sale. Thanks.

 

[392hemix]

Ok thank you.