[Phoenix79]

I have been looking for a good set of 6x4 or equivalent for my daughters 400. She currently has a set of 6x8 on a 77 block. I want to get the compression up in order to be able to use the 2802 cam (she wants the thump she says).

Can't find anything in a reasonable price range.

Could I just mill the 6x8 and accomplish the goal for additional compression?

[b-man]

You won’t get there with 6X-8 heads.

Even the 6X-4 heads need a pretty fair amount of milling to get up to the high 8:1 range.

Finding some ‘68 #17, 69 #47 or ‘70 #11 350 heads would be a good way to go, you can get them from cheap to free. Other than the press-in rocker studs they’re pretty much ideal for a street 400. The smaller 1.96”/1.66” valves are fine for a hot little street 400, if you want to upgrade to 2.11”/1.77” valves that’s easy to do too but really not necessary.

The chambers are probably in the low to mid 80cc range before milling, it should be pretty easy to get the compression somewhere between 9 and 9.5:1.

[25stevem]

See if you can turn up a set of 5C-4 heads .
There the same as 6X-4, but they have a air injection passage that may or may not be drilled.

In fact there’s a set of them for sale on the Franks Pontiac parts site.

[Skip Fix]

Some 70 455 #15s would be a decent start also. Or use the 6X with some mini pop up pistons.

[android 211]

I have some '68 '15' 400 2bbl heads I would be glad to ship. The nominal compression on a 400 is @ 9.5:1. They've never been rebuilt so installing large valves would be easy and valve height would be right. Press in studs.

[ScumOne]

I have #62 heads with the large valves and screw in studs I might sell. They’re original from my 69 Firebird 400. Pretty sure they have 72 cc combustion chambers. I upgraded to KRE heads so I don’t need them. These have about 7k miles on them, hardened valve seats, new springs, etc.

Jim

[25stevem]

If your going to rebuild whatever set of iron heads you pick up ( which you should if such as not been done) and if you will not run headers, then another head to look for is the 7HI casting off of a 72 350.

These have 1.96 and 1.77” valves .
When rebuilding its easy to go up to the standard 2.11” intake valve and rework them for screw in rocker studs.

The money you save on purchasing a set of these over a set of 6X castings should fund the conversion over to screw in studs.

[KCTurbo]

I ran the 2802 with a set of #13s and I liked it very much, very stout. I think I have two sets still.

[ta man]

Where are you located..you would be amazed how many here have a stash of old parts.

[Phoenix79]

Sorry for delay replies, I thought the site would notify me of responses. We live in Leo Indiana.

[Phoenix79]

Originally Posted by KCTurbo

I ran the 2802 with a set of #13s and I liked it very much, very stout. I think I have two sets still.

Are you looking to sell a set? Would you happen to know what compression would be if used on a 77 block with 7.6:1 comp engine?

[Phoenix79]

Originally Posted by ScumOne

I have #62 heads with the large valves and screw in studs I might sell. They’re original from my 69 Firebird 400. Pretty sure they have 72 cc combustion chambers. I upgraded to KRE heads so I don’t need them. These have about 7k miles on them, hardened valve seats, new springs, etc.

Jim

Jim will keep you in mind, looking for D port if I can find 'em.

[geeteeohguy]

Originally Posted by Skip Fix

Some 70 455 #15s would be a decent start also. Or use the 6X with some mini pop up pistons.

I used a set of these heads on my '67 GTO with flat top forged pistons .030 over. Ended up with about 9.3 CR. The heads cc'd at 87 and I upgraded to screw in studs. I can now run 91 octane fuel and it runs fine with an 068 cam and stock intake and exhaust. Been on the engine about 12 years or so and a lot of miles.

[Phoenix79]

Originally Posted by android 211

I have some '68 '15' 400 2bbl heads I would be glad to ship. The nominal compression on a 400 is @ 9.5:1. They've never been rebuilt so installing large valves would be easy and valve height would be right. Press in studs.

What are you thinking for the #15 heads?