GM says that to get the best Quench effect to reduce octane rating of the fuel, a 4.00 inch piston crown needs to come within 0.026 inches of the cylinder head on 60% of the area.

David Vizard on SBC V8 test rigs wrote that he saw no increase in horsepower once quench was 0.060 inches.

Wonderful, did he happen to look at detonation suppression?
Dave also seems to be in the minority since most data I've seen pretty much says at .060" you aren't getting any quench effect at all.

I think it was RAAM built a 440 and set the quench pretty loose like around .080 or something then tightened it up to like .040 or so and saw a dramatic increase in power as RPM went up, something like 80hp. It was quite a bit more hp than the compression alone should have accounted for. Maybe someone can find a link to his post, I think it was a 440 he built for towing so we can look at the details again.

"EGR adds to the total amount of gasses being pumped through the engine therby increasing pumping losses"

This statement is incorrect. "Pumping losses" mean the amount of atmospheric absolute pressure (energy) that is wasted sucking air past the throttle plate. So for example a Diesel engine has close to zero pumping losses.

From Wikipedia: "A properly operating EGR can theoretically increase the efficiency of gasoline engines via several mechanisms:
Reduced throttling losses. The addition of inert exhaust gas into the intake system means that for a given power output, the throttle plate must be opened further, resulting in increased inlet manifold pressure and reduced throttling losses.[7]

A properly operating EGR can theoretically increase the efficiency of gasoline engines via several mechanisms:
Reduced throttling losses. The addition of inert exhaust gas into the intake system means that for a given power output, the throttle plate must be opened further, resulting in increased inlet manifold pressure and reduced throttling losses.[7]
Reduced heat rejection. Lowered peak combustion temperatures not only reduces NOx formation, it also reduces the loss of thermal energy to combustion chamber surfaces, leaving more available for conversion to mechanical work during the expansion stroke.
Reduced chemical dissociation. The lower peak temperatures result in more of the released energy remaining as sensible energy near TDC (Top Dead-Center), rather than being bound up (early in the expansion stroke) in the dissociation of combustion products. This effect is minor compared to the first two.

If spark plugs were doing a perfect job of igniting the mixture, EGR would improve fuel economy even at high rates.

In practical terms, a dual spark plug per cylinder engine like the 5.7 can probably stand 10 to 15% EGR before increasing misfires cancel the effect of less throttling losses.

Though engine manufacturers have refused to release details of the effect of EGR on fuel economy, the EPA regulations of 2002 that led to the introduction of cooled EGR were associated with a 3% drop in engine efficiency, bucking a trend of a .5% a year increase.

Also with the ever tightening mpg requirements EGR is disapearing on a lot of cars. Most hemis don't have it pentastar v6 don't got it.

If "throttleing" losses were a real thing than chryslers MDS would not really work but it does. Basically 4 cylinders get "throttled" down completly.

I am still not buying it. The only way I see it helping MPG is if you are running too low of an octane number fuel. However the right fuel would net more MPG.

FINALLY pulled the heads on my 2000 Ram 5.9 Magnum... Pistons average around .050" down. Mic'd 'em all right at centerline, and got anywhere from .047" to .052".

EXXXXXXXCELLLLENNNNNNT.... . . .

Now, to research available head gaskets and decide how much to lop off the block. I'd decided that if it was as low as some here find i was just gonna port and shave the heads a bit and sew it back up. But this is close enough to bother with the tricks...

Damn clean inside too. Cleanest factory engine i've ever taken down. Crosshatch could be a bit more visible, but meh...

Thinnest gaskets are Mr. Gasket 1121G. 0.027" - 0.028"

Everything else is thicker.

MP sells a similar (maybe the same) gasket. Check prices as the Mr Gaskets come one in a package so you have to buy two. At one point I got the idea the MPs were two to a package, but they're not always available.

Dave, totally closing both intake and exhaust valves turns the cylinder into a big air spring. Since nothing is being pumped, no work is done. There are losses though, first is friction and second is, some of the heat of compression has to leak out into the cooling system. There is also something called hysteresis which means that some of the energy required to compress the spring isn't regained when the spring is unloaded. I think this component is negligible.

When one starts looking at articles in the Journals of the Society of Automotive Engineers, it becomes clear that EGR is very common, but since the advent of variable valve timing, it is easier to get EGR by adjusting the exhaust opening and closing events. The final product engine is the result of probably thousands of runs of computational fluid dynamics, dyno tests, and actual street driving.

The computer is programmed to give the engine the best combination of air, fuel, spark, etc. which will still be working well enough to pass an emissions test after 100K miles. Tuners are able to gain power or efficiency by reducing the safety margins.

R.

Thats disappointing. There is no .020" steel shim gasket?

If it matters, both surfaces, deck and heads will be freshly machined.


If i have to use a .027" gasket i'll have to lop .045" off the deck... That seems excessive...

I have a pair of MP steel shim SB gaskets. 0.0215" email if these will work for you.

Hmmm...

They have been out of production for a looooong time. Subject comes up here about annually.

R.

Blazin Bob, your PM in basket is full. Can't leave a PM.

I deleted 33 but evidently that ain't enough. I will get in there & do a bunch. at the top I am seein: "quota" in red which obviously means I'm over the limit & it just turned red recently then there is: 1028/500. how many do I need to elim to resolve this?

I sent you an Email... but it came back undelivered.

My email address is correct but it might have went to spam but I do not know how to check/correct that. PM's have been coming thru so you might try again (I did not yet delete any more PM"s so not sure whats going on there). I will send you a PM right now.