Walt Dupont--Me.
Well-known member
I understand the differance in the 2 heads, .400 and .425 depth in the valve pockets. Correct? Does anyone know the differance in the CC of each head? Thanks Walt
Offy 400 and 425 heads CC
- Thread starter Walt Dupont--Me.
- Start date
Vergil
Senior Member
Ol' Ron
Well-known member
Walt , These heads are all over the place and I know that the 425 won't clear the L-100 with out some relief over the valve. You'll just have to measure them. I like the Offy heads because they are quite thick and you can carve just about any combustion chamber you want. I start by milling for .050" over the piston, then .050" over the valves then CCing them. Now you can shape the transfer area for any CR you want. Good luck (A good mill helps)
GOSFAST
Well-known member
The part #1069, "400" Offy's, I have here now and they measure 60 cc's "as-cast".
The #1069, "425" heads going from memory measured 64 cc's.
The "400" denotes the valve lift, .400", that the heads will clear, respectively the "425's" will (should) clear a .425" valve lift! This should all be checked regardless! This sort of explains the slight add'l cc's in the "425" castings!
Another "+" on the Offy's is they are a "tighter" fit when using head
studs? The head bolt holes are slightly smaller than the Edelbrocks!
P.S. I keep a few sets of the "400's" in inventory and have the chamber sizes in our records. They are definitely 60 cc's!
The #1069, "425" heads going from memory measured 64 cc's.
The "400" denotes the valve lift, .400", that the heads will clear, respectively the "425's" will (should) clear a .425" valve lift! This should all be checked regardless! This sort of explains the slight add'l cc's in the "425" castings!
Another "+" on the Offy's is they are a "tighter" fit when using head
studs? The head bolt holes are slightly smaller than the Edelbrocks!
P.S. I keep a few sets of the "400's" in inventory and have the chamber sizes in our records. They are definitely 60 cc's!
Walt Dupont--Me.
Well-known member
According to the web site that Vergil posted , the 425 heads are 63CC and the 400 are 54CC I don't know where the chart came from but take a look. I just bought a set of 400 heads for this stock car engine I'm building. They should be here in a couple of days. I figured i'd have the do some valve pocket work. I also use Chevy valves and the heads are thicker that the ford valves so that helps make the valve pockets a problem. Thanks for the info guys. Walt
Capn John
Well-known member
As I understand it Offenhauser wil provide whatever you need in cc size, just request it. For instance the chart Walt mentions above shows up to a 304 cu. in. If you want a 8:1 compression ratio the chamber would have to be increased.
You may want to check with them directly.
You may want to check with them directly.