The Dodge Challenger Message Board

WIth "open" chamber heads to calculate your "total combustion chamber."

Gasket height + deck height + Combustion Chamber = Total Combustion Chamber.

for my engine:
Gasket Volume = 4.56 CC
Deck Volume = 27.14 CC
Head Chambers = 81.5 CC
Total Combustion Chamber = 113.2 CC

Using Desktop Dyno I got 8.96:1 compression ratio.

Now to my question; if I change my cylinder heads to the edelbrock performer RPM with "CLOSED" combustion chambers would my compression ratio increase?

Here is what I think:
Edelbrock Performer RPM Heads 84 CC
Since they are closed chambers you don't have to add gaket volume and deck height volume, right?

Using desktop Dyno my compression ratio increases to: 11.72:1

Is that correct or does closed chambers not effect total combustion size in that way?

A 'closed' chamber makes no difference to your other volumes like gasket or deck height volume. It just means there is no raised quench area. Normally this would result in a smaller chamber size and you just treat it as a normal combustion chamber in your calculations.

A gasket has volume no matter if the head in on or not. Same with the deck height. How can the head effect deck volume (positive or negative)?

So with no other changes you will make lower compression because even the closed chamber versions have bigger combustion volumes than you have right now.

Assuming that you have all the other measurements correct?

You want to aim for 10:1 compression at least with alloy heads.

So the only way I can get higher compression from the edelbrock heads on my current engine setup is: by getting the heads milled to shirnk combustion chambers. My head gaskets are already very tiny only .019 inches.

I believe that have plenty of meat on them for milling but I would be tempted just to use higher compression pistons to make up for it.

I would go for 10.5:1 or 11.0:1 static compression depending on final cc of engine, fuel octane, and cam profile.