8 bolt vs 16 bolt exhaust Edelbrock head differences?

[jholmes217]

Besides 18 bolt vs 8 bolt on the exhaust, are there any differences between what the call the 427 head vs what they call the 390/428 head?

[wsu0702]

The only other difference is the combustion chamber.  The 427 heads have machined 76cc chambers and the 390/428 heads have a cast 72cc chamber.  Both have ports that are based on Ford C5AE-F Medium Riser head design and CJ size valves (2.09/1.66).

[jholmes217]

The only other difference is the combustion chamber design.  The 427 heads have machined 76cc chambers and the 390/428 heads have a cast 72cc chamber.  Both have ports that are based on Ford C5AE-F Medium Riser head design and CJ size valves (2.09/1.66).

So would the 8 bolt work OK as a direct swap for 428 Cobra Jet heads on a 428?  Current compression ratio is 10 to 1 (machine shop dished the pistons a little) with the iron heads.

[wsu0702]

Have your stock CJ heads been milled? 

[jholmes217]

Unknown.  I'm running 92 octane pump gas in it no problem.

[427Fastback]

I bought the 8 bolt 427 heads because they say the seats can be cut for the 427 size valves.I then redrilled /heli coiled them for the 16 bolt pattern.Now...I have never seen the two sets side by side so I don't know if they have different seats.
I also CC'd my heads and they were bang on..I have heard the 72CC heads are actually in the 76-78 CC range.I did lose half a point on my compression but its a street car and I doubt I will notice with all the other changes I made..

[wsu0702]

The only other difference is the combustion chamber design.  The 427 heads have machined 76cc chambers and the 390/428 heads have a cast 72cc chamber.  Both have ports that are based on Ford C5AE-F Medium Riser head design and CJ size valves (2.09/1.66).

So would the 8 bolt work OK as a direct swap for 428 Cobra Jet heads on a 428?  Current compression ratio is 10 to 1 (machine shop dished the pistons a little) with the iron heads.

Should be about the same compression ratio.  Ford lists the stock CJ head chamber as 72-76cc but a lot of guys have measured untouched stock heads and they report chamber volumes in the upper 70s.