[Steve C.]

I've posted this before, here again for interest.....

Years ago I had a conversation with Dave Bisschop regarding static compression ratio on aluminum heads.
He felt you can't protect all of these engines once they leave your shop so he often purposely kept it conservative for most that don't want (or shouldn't) push the envelope and stay on top of the tune, bad gas, weather, etc.

In that conversation with conservative in mind and regarding Edelbrock cylinder heads. Based on his dyno testing at the time, he stated 10.25 max for Edelbrock 87cc castings and 10.5 max for their 72cc castings.
The difference being the chamber depth between the two. This was his opinion with the chamber design of the Edelbrock round port heads at the time. Not the newer "heart shaped" design.

Tom S made a good point here....
"If your not going to race it,why take any chance when driving around in traffic on hot summer days.Your ass dyno will never feel the .6 of a point.JMHO,Tom"

I can relate this. About 20 years ago I did a 4.210 stroke 462 with 87cc Edelbrock heads. On my machinist bench they were 313cfm at 0.600" lift.
However when I ordered custom pistons there was a mistake made and the static compression ratio ended up at about 9.7
On the engine dyno with a Performer RPM intake & custom HP950 carb it made 589 ft.lbs torque at 4400 rpm and 580 hp at 5800 rpm.
For the most part it was street only and I'm sure my ass would have not noticed the difference with a bit more compression.
For interest only, it ran 10.948 at 123.59 mph at the track.


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