Back to the machine shop...
Not trying to ruffle any feathers or be contentious, but 1st and 2nd gen Hemis have 360 degree squish and quench, and 3rd gen Hemis have two large quench and squish areas on the sides of the combustion chamber. I have had (or still have) all three generations of Hemi engines and run them.
So I respectfully disagree with the assertion that Hemi engines don't have squish and quench. Besides the wonderful unshrouded valves and direct, cross flow, the large squish and quench are what make the design so effective.
Second, head material does make a large difference in detonation tolerance. Most aluminum head engines can tolerate at least a point higher in static CR.
Also, smogger low compression 440's pinged like crazy with very low compression ratios, reason... no quench and squish.
Just my 2 cents derived from experience and study.
I respect your opinions and am in no way trying to discount your assertions.
Thanks,
Mark
Ok, first we need to use the correct terms or we will never come to an understanding.
I don't care what you do, I'm just trying to erase decades of absolute nonsense. You can believe what you want, but I've tested quench to the point it was just a stupid waste of money. It's not cheap to buy Pistons and do all the work to correctly test it. And I can say unequivocally that there isn't any power in quench. There isn't any detonation resistance in quench. There is an emissions factor in it, but I can tell you crevice volume is just as bad or worse for emissions as is lack of quench. That's just the facts.
Second, and for the last time, a Hemi does NOT have quench. Does NOT. The Gen III has it, but that again, has zero to do with power. It's an emissions deal. So I say piss on Jimmy Carter and his CAFE standards and his blackmail of the states over 55 MPH law.
What the Gen I and II Hemi does have is SQUISH. It's not the same. Not even close. Two totally different things. Anyone with any basic knowledge of 2 stroke operation knows what I'm talking about.
Look again at the small block Chrylser. It a really cool design if you know what you're looking at. Done correctly, the SBM has quench AND squish. You need the correctly shaped dome, but you can get both (I have it...that's one reason why the highly loved Magnum chamber is highly overrated...you can't get any squish) and then look closely at the spark plug location. It's about as close to Hemi plug location as you can get in a true wedge head.
So I'm saying to you that sadly, you are trying to gain something where there is no gain to be had. None. Every single test we made any power gains came from raising the CR and not quench. Every time. I know that goes against current thinking, but I looked at the crapola Marlan Davis was palming off in the link you posted. He had a lot of "theory" in his short article, and some speculation and some good old fashion conjecture. That's what he's paid to do.
In fact, if you read the last sentence of the first paragraph, he either knowingly or unknowingly explained why everything he was going to say was wrong. Go read that sentence over and over until it makes sense to you.
Then consider plug location. I get that low Cr smog her big block junk would rattle it's brains out. It has a garbage plug location. Just like a SBC. Horrible spark plug location. Has nothing to do with quench. Zero. So let's use you example of a pig smogger big block (which BTW if you look at cam timing and ignition timing on that garbage and you can see other sources of detonation, all in the name of emissions and quench won't fix that) and let's keep the 7.8:1 CR right where it is, but get the beloved and worshipped quench. What would you have. A low CR ping monster. You didn't fix the plug location, the *** backwards cam timing and ignition timing only a moron would, or a smart man would use when the government told him you have to do "this" and the only way to do "this" is to do other things so stupid anyone with the IQ above a slice of bread would see how ignorant what they do really is.
Again, quench is just what it says it is. Closing off a part of the chamber to cool it down. Pushing the air/fuel load to the plug doesn't really matter, because things like stratification, fuel droplet size, chamber temperature and some other stuff cat be fixed with quench.
Squish, which is what a Hemi has (and a SBM if you do it correctly) pushes any air/fuel from the edges of the chamber and around the dome and it cleans up the possible trapped crevice volume around that area.
Not the same as quench. Look at a 2 stroke. It's the same principal.
Now, to another long told fib...that aluminum "carries away heat so fast that you can run a point of CR more than with nasty old iron because it gets so hot and retains all that heat" or some similar shinola like that.
It isn't true. I've typed it out so many times on this very web site, in more than one place that I ain't going to do it again.
If you stop and think about a running IC engine, you'll see how silly that idea really is. That's why I can run 11:1 on iron heads, run full timing at near sea level and to get it into detonation I'd have to be just plain ignorant. I'm going to go to 12:1 or maybe a bit more on my next build, on straight pump gas and I'll run full timing and not have detonation issues either.
I've been a proponent of, and have been doing higher than whatever the popular CR number of the month is since the very early 1980's. It's not new. None of them had quench. None of them run less than full timing. And it wasn't just on small block Chrysler's.
I remember when 9.5:1 was IT. Anything over that was a taboo worse than screwing your own mother. Yet I was doing it. With success. You have to have the entire system correct (you should be doing that anyway, regardless of the CR you want to use but you'd be surprised how many people have no concept of a systems approach to engine building) and IF you do that, you can run any CR on iron as you can with aluminum.
That's just a fact. If you're engine builder can't or won't do that, find another one.
I have a measured 10.5:1 small block on the stand at home with a couple hours of work to finish it off. I'm working with a FABO member on his SBM hopefully going together this spring with what will be a measured 10:1 engine.
Both will have very mild cam timing, both will run on pump gas, both will run full timing and both won't be hard to tune or be ping monsters.
BTDT many, many times.
