Its getting warm enough to start on the assembly of my 428 and I need advise on which of the 3 different cylinder heads I have to choose from.
#1 C8AE-H with 14 bolt exhaust manifold set up. (390 GT?)
Pluses: These heads have been rebuilt and never installed on anything.
Minuses: The exhaust bolt pattern doesn't match up to headers or exhaust manifolds that I have. Combustion chambers are the smallest .cc for the heads I have
#2 C8AE-H "standard" heads
Pluses: Have 1 already rebuilt, fits the headers and exhaust manifolds I have
Minuses: combustion chambers are the same as the heads above, and I need to get 1 more head rebuilt to have a pair.
#3 C6AE- ground off. For reasons unknown to me someone in the past ground off the last digit.
Pluses: Has the largest combustion chamber of the heads I have
Minuses: Both will need to be rebuilt, and the exhaust port is a lot smaller that the C8AE head.
I used Steve Christ's book as my information source. The cam I will be using has the following specs:
Intake exhaust
gross valve lift .519 .519
duration 270 270
The engine will also have a cast iron 4bbl till I can afford a better one and a 600 Holley. The machinist tells me that I will have about a 10.5 to 1 compression ratio which has me concerned. That is why I am thinking about the C6AE heads. Money is an issue so I need to keep costs as low as possible.
Thanks for your input!

 

I would say the 16 bolt heads. I don't have any flow data on these so I don't know if they outflow the standard C8 heads but I know they don't flow any less and they are ready to go so I would say go for it. You don't have to use all the bolt holes as the vertical bolt holes are in the same exact location on each head as far as I know. What pistons are you using to give you that compression? That is too much for the street with that cam. You need to keep it under 10 to be safe at the pump.

 

The vertical bolts are a different spacing by about 1/4 inch. Its the first time I've seen anything like it. I thought that all FE heads were common in this spacing but not these. It figures, just my luck. I'm not sure what make the pistons are, they came with the block. I'll have a look for some ID marks when I get out to the garage again.

 

Those 14 bolt C8 heads have the top bolt holes lowered only on the ends. They are sometimes called the GT head but they came on any FE in an intermediate chassis in order to fit between the shock towers. They take the so-called GT manifolds, the logs won’t bolt up to them.

The small exhaust ports on the C6 heads is an AR lip which can be ground out.

10.5 is too much compression imo, I would rather see around 9.5.

Barry

 

The pistons have "L2303" and ".030" on them. From what I've been able to find on the web they are 30 over TRW forged pistons that are supposed to be a factory replacement for the stock piston and have a 10.5 cc dish. If I'm running the C8AE-H heads with an approximate cc of 68 to 71 what would the compression ratio be? The crank is a 1U 428.

 

The CR is dependant on the cam and head gasket used, but I think your going to be a bit high.

Just as a side note, I was in the same spot with my setup and I got some C7AE-A heads that had 77cc chambers. I ported and polished the heads, then worked the chambers. By the time I was done with the chambers, they were 80.5cc

I blocked off the exhaust crossover, had the dist custom curved and have 210# cranking compressoin and don't have a problem with pinging (not yet anyways)

Every little bit helps and a cooler air charge and smooth chambers help with pinging.

If you can, I'd look again at the cam selection. It sounds like a single pattern cam and FE's do better with a dual pattern cam (more exhaust lift and dur)