Explain Quench to me.....GO!

I'm glad to see this thread going again... since the last time I posted a few years ago (f.k.a. "MOPEkidD-3") the 360 I had in my Duster went kaput and I put together another one which I got running this past April. My previous 360 was an LA block with stock iron Magnum heads, bored .060" with KB flat-tops and pretty close to zero deck (maybe .005" below). Quench height was around .042-.045". Compression was 10.5:1 and I was using a mild Lunati Voodoo HFT cam which made the cylinder pressure way too high (short-duration high-lift intended for smaller low-comp engines) and caused repeated pinging which is what eventually killed it. Anyway I have noticed pretty big differences in the way these two engines run because my "new" one is an all-stock 5.9L Magnum short block with heavily ported Edelbrock RPM "open" (milled) chamber heads, the ones meant for old high-comp 340s with pop-up pistons. With the milled chambers being .050" deep, stock Magnum pistons .050" down in the hole and .027" Cometic gaskets I'm right at the upper edge of the "detonation danger zone" as mentioned in post #35 but considering the compression ratio is only 9:1 and I have a proper custom-ground cam with sufficient duration for the combo I have yet to encounter any pinging even running regular gas (85-octane here at high altitude) and almost 40* total timing (initial + mech).

Here's where the comparison gets interesting. As you can imagine my old 360 was a torque monster and had incredible throttle response; you stepped on the go pedal at any RPM and it just picked the car up and moved. My new one doesn't have quite the same level of responsiveness and torque especially below 3000 RPM or so but because of the ported heads and bigger cam the overall HP is much higher and the powerband is much wider (current one pulls hard to 6000+ RPM, old one ran out of breath by 5000 RPM). Now we get into the squish vs. no-squish discussion; since I used the same 750 cfm Street Demon as my old 360 it became obvious during tuning this new engine wants a LOT more fuel. Like there's noticeably less power especially in the higher revs if the AFR on my wideband O2 gauge is leaner than about 12.5:1; my old 360 made max power with 13-13.5:1. Also with my old 360 I was able to lean out the part-throttle cruising circuit all the way to 16:1 or leaner and it would still have good response and run smooth when easing into the throttle (like going up a hill) without making extra heat. This new 360 really doesn't like to run much leaner than 15:1 at any time and even at that AFR I noticed it ran a bit hot at freeway speeds (~3000 RPM) so I put it back to 14-14.5:1 at cruise. As you can imagine gas mileage is also much lower; around town my old 360 got 14-15 MPG, current one gets about 11. But then again I had to always run premium with the old engine, the new one drinks cheapo regular just fine.

I think what I've learned from this is the whole tight quench deal has the most benefits at part-throttle. If you're building an engine and your only goal is WOT power then the squish thing is not really worth your time unless it's for competition where rules limit what you can do and you need to squeeze every last bit of HP you can get. But if you are building an engine that will see lots of street miles (or something like a circle track engine) and decent gas mileage is a goal then building for squish is totally worth it IMO.