[mechanic17]

"Funny how the N/A internal combustion V-8 engine shows so many similarities following a few basic guidelines for setting them up, no matter what brand they are........Cliff"

In the article BruceWilkie linked to earlier (post #45), the author uses two examples of good vs. poor (for CR purposes) combustion chamber design, the Cadillac Northstar and the Hemi. I recall him saying the 2000 Caddy redesign allowed them to get up to 10-1 SCR on 87 octane (the second example I know of in this thread after LT1s.)

So it appears those more modern chambers that everyone begged Edelbrock for (in Pontiac heads) are also a big part of that ideal combo. Now we even have them coming into the market for the masses.

--so, I'll try a brief recap, as the thread grows, of responses to the original question:

I. Major factors/variables beyond SCR include:

-Dynamic compression ratio /cranking compression (as determined by cam events like LSA and IC--NOT overlap as is often assumed)

-RPM range the engine operates in (determined by gearing and driving purpose)

-Quench distance (pistons down the cylinder)

-head material (iron vs aluminum)

-cooling system efficiency

-fuel quality, in addition to octane

-combustion chamber design

I'm sure I missed some--did it from memory.


II. The major points of contention seem to be:

-Should a "safe" SCR (8-1? 9-1?) be observed by non-tuners, even those who read these forums and are trying to learn more about high performance? Is SCR even useful as a guideline, given the many other variables?

-Should camshaft LSA be wide or tight for a Pontiac, and for what purpose (part-throttle cruising? drag racing? dual-purpose? remembering that this is the "Street" section)?

-What is the useful limit of dynomometer data for street-perf vehicles?

I'll be happy to edit omissions/inaccuracies if they're pointed out.