Question: New Heads???

[LannyL81]

'81 with a 270H cam, 2 valve relief 30 over pistons, zero decked block, stock intake and E4ME carb: currently have 882 cast iron heads shaved down from 76cc to 74cc...has 2.02/1.60 valves, bronze valve guides, guide plates. Springs came with the 270H cam, 1.6 roller tip rockers, Hooker sidepipe headers and tubes.

From what I remember when I did this engine the static CR was 9.1:1 and was wondering if I went with a set of 64cc aluminum heads could I still run 91 octane fuel without additives? Even during the summer when its over 100 and 10% humidity?

 

[Hib Halverson]

(snip) was wondering if I went with a set of 64cc aluminum heads could I still run 91 octane fuel without additives? Even during the summer when its over 100 and 10% humidity?

Unfortunately, you can't.:eyerole

You'll be way short on octane going from 74 to 64 cc heads.

You either need to run some big chamber alum. heads or use dished pistons.

With aluminum heads, and 91-oct gas, the CR limit is about 10:1.

 

[Rodney Gold]

You can run a nice set of 64cc Ally heads and make the power on pump gas if you run a water or water/methanol injection system - they arent that pricey. Just using water injection will work and you can find water most places
Using Pure methanol will give you a nice HP bump - most run a mix cos of methanols flamability
most systems are programeable too.

 

[LannyL81]

Anyone make big chamber (70cc or so) aluminum head? I have only been able to find 64cc heads.

 

[Peer81]

If you're now using a thin steel headgasket you could recalculate it with a thicker (felpro) gasket..?

Groeten Peter

 

[Crimson Thunder]

If you already own the heads you could find a competent head porter to take some more material out of the combustion chamber to make it bigger.

 

[Hib Halverson]

Here's the skinny on heads

1) You can't loose enough compression via thicker head gaskets to go from a 74 cc chamber to a 64 cc chamber

2) You can't remove enough material via grinding to do it either. You'll either be into the water jackets or you'll dangeroulsy reduce combustion chamber wall thickness.

You need to either find a bigger chamber head, go to dished pistons or take the compression ratio increase and run the car on race gas.

Edelbrock sells some heads with 70 cc chambers.

 

[LannyL81]

I did finally find some 72cc heads...but sure are not cheap. Wondering just how much performance gain I would get other than the extreme light'ing of my wallet from buying these heads.....