BBC Heads

vht · Post by **vht** » Tue Jul 30, 2019 8:36 pm

Has anyone know of a BBC head with a smaller chamber than 109 in an alum head? I have never heard of one but my 427 has the 425 HP semi closed chambers and flat top pistons. I'd like to go to alum heads this winter. The pistons are actually JE blower pistons with upgraded pins so I kina hate to change them. I'd like to end up with 10.5 to 1 comp if possible.

prairiehotrodder · Post by **prairiehotrodder** » Tue Jul 30, 2019 9:21 pm

edelbrock # 60435

F-BIRD'88 · Post by **F-BIRD'88** » Tue Jul 30, 2019 10:45 pm

To get 10.5:1 cr using a 427 bbc flat top piston will require a 77cc chamber cylinder head.
There are no bbc heads with 77 cc chambers.
A 100 cc head and a flat top piston does not even get you close.
Change the pistons or supercharge it.

The cr is very low.

Any piston dome will need to be checked for chamber clearance at tdc with any of the eddy bbc heads.
And may need custom hand clearance grinding.

mag2555 · Post by **mag2555** » Wed Jul 31, 2019 7:50 am

You do not want a 290 cc head on top of a 427 cid motor unless your buzzing it to 8000 rpm even if you could have a 10.5 to 11 to one comp!

I you go for the AFR 265 CC head with its 109 CC chamber and let the added port velocity make up for whatever short comings you may have to live with compression wise.

Post by **Stan Weiss** » Wed Jul 31, 2019 10:31 am

vht wrote: ↑Tue Jul 30, 2019 8:36 pm Has anyone know of a BBC head with a smaller chamber than 109 in an alum head? I have never heard of one but my 427 has the 425 HP semi closed chambers and flat top pistons. I'd like to go to alum heads this winter. The pistons are actually JE blower pistons with upgraded pins so I kina hate to change them. I'd like to end up with 10.5 to 1 comp if possible.

So other than removing some weight. What is the objective for the head change?

Stan

prairiehotrodder · Post by **prairiehotrodder** » Wed Jul 31, 2019 10:53 am

here is a used set for $1500 canadian dollars. He says they are a 90 cc chamber. Pretty good deal for you in USA dollars.

https://www.kijiji.ca/v-engines-and-eng ... nFlag=true

RevTheory · Post by **RevTheory** » Wed Jul 31, 2019 11:15 am

prairiehotrodder wrote: ↑Tue Jul 30, 2019 9:21 pm edelbrock # 60435

I was really looking into those heads for a <6,000 rpm 454 and I just couldn't get the likelihood of having to cut valve reliefs in the OEM pistons (or run a low-lift, wide LSA cam) and epoxy the runners down ~30cc to balance out in my head.

F-BIRD'88 · Post by **F-BIRD'88** » Wed Jul 31, 2019 11:18 am

A 90cc head does not even get you close on a flat top piston 427. If it is even close to 90 cc it has been milled to the max.. (Issues, ptv clearance, thin deck, intake misfit)
The eddy performer TBI bbc head is 100cc.

A 10.5:1 cr 427 with 109cc pistons needs a +26cc piston dome.

F-BIRD'88 · Post by **F-BIRD'88** » Wed Jul 31, 2019 11:38 am

A set of 8 KB227 piistons have the correct 26cc dome and are $300 US.
Piston dome to head chamber wall clearance must be checked on a bbc builds using kb pistons.
Minor clearance grinding may be needed.

Why spend $1500 to $2500 to NOT even fix this $300 problem.?

vht · Post by **vht** » Thu Aug 01, 2019 9:42 pm

Not really a fan of KB pistons, I found some wiseco's that would work. I'd like to get some wt off the front so I think since I have to buy pistons, I could sell the 425 HP heads and put a set of alum heads on it. How do some of the lower cost heads perform? I'd stay with square ports since I done have the intake, I've heard the horror stories on the Pro Comp heads, I'm assuming the Assault heads and some of the others may fall in the same category. When I drag raced, I always ran Brodix but since some health issues I don't have that kind of money.

englertracing · Post by **englertracing** » Thu Aug 01, 2019 10:38 pm

https://www.cidheads.com/collections/ci ... nder-heads

prairiehotrodder · Post by **prairiehotrodder** » Thu Aug 01, 2019 11:59 pm

vht wrote: ↑Thu Aug 01, 2019 9:42 pm Not really a fan of KB pistons, I found some wiseco's that would work. I'd like to get some wt off the front so I think since I have to buy pistons, I could sell the 425 HP heads and put a set of alum heads on it. How do some of the lower cost heads perform? I'd stay with square ports since I done have the intake, I've heard the horror stories on the Pro Comp heads, I'm assuming the Assault heads and some of the others may fall in the same category. When I drag raced, I always ran Brodix but since some health issues I don't have that kind of money.

i think the promaxx heads are one of the lowest priced rectangle ports that still have a somewhat good reputation. I've never used them personally.

vht · Post by **vht** » Sat Aug 03, 2019 12:40 pm

I think if I do it, I'll buy bare castings and that way I'll know what I got. I've heard they were good heads and also the Jegs brand. May be the same head for all I know.

prairiehotrodder · Post by **prairiehotrodder** » Sat Aug 03, 2019 1:33 pm

I could be wrong but i think the promaxx heads used to be called "patriot" heads. A number of years ago i put a set of their heads on a 2V 4.6 mod motor with a kenne bell blower in a 99 mustang and they worked great. We bought them fully assembled and the car was driven all over Canada and went mid 11's in heavy street trim.

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