Firstgens.com

I purchased the top end kit from Edelbrock about a year ago and the heads have "semi-open chamber" with CC volume 110...I have seen other heads advertised as "open chamber" heads with the same CC volume of 110...

My question is what is the difference between the semi-open and open chamber heads if they have the same CC volume? Is it the design of the chamber?

My 396 came factory with 10.25 CR but I'm affraid I lowered the CR down to 9.2 CR by installing this kit...Not sure if this will make that much of a difference on Hp...

Thanks
Mike

"back in the day" standard big blocks came with "oval port heads." These had smallish ports (still much bigger than any small block head) and chambers in the 100cc range. This is what your 396 came with.

The solid lifter motors came with "open chamber heads" These had larger chambers, upper 120's I think, but that was just a small part of the difference. Open chamber heads had GIANT rectangular intake ports, much larger than the standard heads, and required a different intake manifold as well. These heads were typically used with large dome pistons to get 11:1 or more compression. These were radical engines.

As for your edelbrock heads, I gotta say I'm not positive on the numbers. If they have bigger chambers than the stockers, and you are using stock type pistons, then yes, your compression ratio will be left.

Who's gonna take it from here?