Newbie question on combustion chamber size in heads

[zerfetzen]

I was reading about 318's that the older, more powerful (230bhp) motor had 60cc combustion chambers, and the newer ones had 61cc's, which lowered compression.  But, I was looking at performance heads, and they all seem to offer even larger cc's, when I would think smaller would be better for higher compression.  Example:

Summit: Edelbrock Performer (EDL-60769), 63 cc's
Summit: Mopar W2 Cast Iron Race (DCC-5249769), 65 cc's (By the way, the description says the head is made of aluminum, not cast iron...what's that all about?)

Are the larger cc's cut so you can put a taller piston in or something?  Thanks.

[Rob C]

Those heads are designed with the 340/360 or larger in mind. The extra cc in the heads purpose is not for domed pistons, but to stay within rules set by NASCAR or NHRA and others.
Sometimes it's compresion rules. Example of less than 10-1 or cylinder head cc as the car came with stock. An example of the 360 head is 72 cc stock. It can vary a little per casting. Check rules of the NHRA and you'll see a list of min. and max cylinder head cc's.
You choose piston and cyl. head cc to get the ratio your looking for.
More compression equals more performance or power is true, but, some class's will restrict the ratio. The truck class in NASCAR regulat the ratio to 9.0-1. And there makeing over 600 HP.
So a hi ratio isn't allways needed.

I have not read about an aluminum W-2 in a long time.

[zerfetzen]

Thanks for the good info.  I'm not actually shopping for new 318 heads, but am wondering, what would be good ones for a motor with a mild build-up?

The place that built my motor a few months ago said they got the tallest piston in there they could, but I don't believe them because they said it was still just a little down in the hole.  Given this, if I did ever decide to throw on better heads, what's the best approach?  Thanks.

[4spdChally]

Have you considered a magnum head conversion? I was looking at that route but I will probably go with a 360 or 440 now.

[Chryco Psycho]

steel heads will retain more heat than alum & have more effective compression with the same size chamber , there never was an alum W2 but they offer some nice heads with small heart chambers , if you want alum the W5 is the similar head to the W2, the 308 heads are a good upgrade & the 302 is good for the smaller 318 engine both are production heads from 87 - 92

[Rob C]

Batten made a aluminum W-2 head. That was looooooooong ago.
Your machine shop is probably unaware of the (Very) new KB 318 piston design for zero deck clearance.
The best approach IMO, is to know where you stand with the current head cc's and the ratio with the current head gasket.
This way, you can say I have a 8.8-1 ratio, if I want to go up, I'll need to do XXX to reach XXX ratio.
This can be done by thinner head gaskets or thicker for less. OR, milling the heads down to increase the ratio.

With that in mind, the best appraoch IMO is to work with your current stock heads. The above mentioned Magnum head swap is a good one. If the price is a little much, ethier port the current heads or look for the "302" heads.
Machine as needed to fit the needs.
You'll need not more than a 1.88 - 1.60 valves in that head. (Or the stock head) The Magnum has larger valves on the intake @ 1.94 and 1.65 exhaust. That head will work well.

On a mild build up, keep the cam small for the 318 and she'll perform well.

Pictured is the chamber side of the 302 head. Note the closed chamber. (Bottom) sorry there new to the stable and have not been cleaned yet.