I was thinking about dropping the compression ratio of my BB502 from 10.2-1 to about 9.8-1 due to the 91 octane gas that is avaialble here in California (Bay Area).

The engine came from the builder (Sallee Chevrolet) with Edelbrock Victor Jr. CNC ported heads that have 110cc chambers.

I called AFR for advice and they recommended a set of their CNC ported 315 heads but stated I should leave the compression at 10.1 to maintain the power (motor dynoed at 630hp). Although, they did say their heads will produce more power than the Vics.

Basically, I went no where with my original quest to drop the compression. Then it hit me. Maybe go for the 121cc AFRs and install a centrifugal super charger.

My quesation is two fold:

1. Will the AFRs produce enough additional power to help offset the cost assuming they machine the heads to match my current compression ratio?

2. If I do go with the AFRs and use the 121cc chamber size can I run a centrifugal supercharger with a compresssion ratio at ~9.1 which was estimated by AFR based on the Vics chamber size?

Thanks,

Larry

Have you tried all the other cures for detonation besides lowering the compression? What exactly is it doing to lead you to believe it is detonating?

1. Will the AFRs produce enough additional power to help offset the cost assuming they machine the heads to match my current compression ratio? I doubt it... Simply the addition on the bigger AFR heads (are the AFRs bigger? what do the CNC Ported Edelbrocks really flow?) MIGHT increase Peak horsepower levels, assuming your combination needs the extra flow, but overall, unless you are racing alot, this will probably not be a major benefit and probably not too noticible of an improvement on a street car (assuming compromises have already been made in other areas).

Generally, I would take AFR's advice "with a grain of salt"... AFR's tech guy is saying their heads are better, but he is also trying to sell you those heads, so naturally thats what he is going to tell you...

Have you ever thought of changing the cam to alter the dynamic compression ratio? This would be alot easier/cheaper than swapping heads (and machining new heads to match current CR, etc).

I agree with Tony - Change the CAM to a slightly longer duration piece and you should cure your detonation problems. I am also curious about what leads you to the belief that you have detonation problems? ( I am not saying you don't - just wondering what symptoms you are basing your conclusion on).

Troy.