With the squish area being so small, the benefits will be less pronounced.

Eventually I hope to be able to discuss this with people that have tried it.

Give me four months and I'll have my vortec 355 on a dyno with before and after numbers, including BSFC, EGT, jet sizes I use, A/F ratios, and ignition detonation limits with 87 octane and 93 octane.

I can't wait that long!!!

Is there any way to test lean misfire limits on the dyno?? I guess it would depend on the dyno.

One way to test lean burn mis-fire limits is to monitor HC emissions. When the engine begins to mis-fire HC emissions will go up.

You guys don't have a clue of who I am, where I came from, nor my background. (and it doesn't matter either) I promise you, there are tricks that have been done on the west coast and in the northeast for TWENTY YEARS that are now just making it to the rumor mill in middle America. (you think NASCAR has the corner on all tech?)

Here's another food for thought along this same "combustion efficiency" line.

Let me be redundant in stating that this mod is NOT to make more top end horsepower but to increase detonation resistance at lower rpms and high BMEPs. A dyno might not show any hp increase, but below 3500 rpm the detonation might be eliminated.

Have you ever noticed the combustion burn on high dome pistons especially? Often a heavy carbon deposit forms a line across a dome. Those grooved pistons from EMC shown in this thread have that carbon ridge. And I conclude that engine cannot have many hours of running on it.... mmmmmm?

SOME engine builders recognize that the sharp edge of domes need to be radiused and massaged to an "egg like shape" to assist in the burn propagation across the chamber. OTHER professional builders in racing circles and even in the Engine Masters Competition just put the out of the box piston domes in their engines. Sometimes you'll see them notch out around the spark plug a little more. Just look at all the pictures for several years. And yet it is a proven fact that full dome contouring helps....

Engineer David Vizard also comments that domes taller than .120 in a SBC actually offset the compression power gain because tall domes hinder the flame front so drastically. He has written that he has seen 100 hp lost due to tall domes.

Builders modify almost every other engine component, carbs, spacers, intake manifold runners, port/gasket match, head porting, chamber shapes, valves, valve back cuts, valve seat angles, and then use out of the box piston dome
contours. mmmmmmmm? Some BIG NAMES don't, a few do.

By the way, grooving the piston quench circumvents the shallow valve edge/head problem and allows alternate groove placement. If you think that the head will crack, cut the .080 deep groove into the piston. simple. This really isn't "rocket science" people.

As for builders' atitudes. I have met several BIG NAME BUILDERS that have told me "I have been in business for "XXX" years and that is the way I have always done it"...... stuck in the past.

I even know of one BIG NAME builder that in '98 told me eyeball to eyeball that he hones cylinder walls with ONE type finish regardless of which rings will be used because---- "I have been doing it for 22 years"...... (He also does not contour domes)

FWIW Just thinking.

Your whole post was great but not as great as what I have in the quote section. That was pretty good stuff and you are right 110%. I have done it this way for 40 yearzzzzzzzz and I am not about to change now bla bla bla. Stuck in the mud ole timers.

Go for it. I want to hear more of your personal experiences.

amen amen amen Preach on Brother.

If it weren't for the Japs and the FEDS smog mandates we's still be driving those horrible mid 70s technological marvels made by Chevy, Ford, and everybody else (180 hp 455s that got 12 mpg on the interstate).

Why did that engine maters engine piston have a hole in it right wihere the crooves came to a point?

The speedtalk thread has a very nice blown up pic of it?

I have been commenting as I progressively read this thread.

Please allow me state ONE MORE TIME......

Back when I was a teen, Don Metzgar in Chicago was grooving cylinder heads in '62... I saw them, I raced against them.

I never had any on my engines.

I had the track records at 5 different "circle" tracks and overall season points championships at 4 of them... for multiple years. My engines had several mods that consensus said "Can NOT work" . But I carried the checkered flag over 500 times from 1960- 65 and won 92.2 % of all the races I ever drove.

Engines are necessary but it also helped to be the best driver on the track.

For those of you thinking.... let me comment...

1) Racing didn't pay squat 40 years ago.
2) Engine/car building paid even less.
3) Then there was a war, a recession, marriage, children. Life happened.
4) I went to work in aluminmum tubing.... I regret that I never stayed with my passion and dreams 100 %, .... but somebody had to fly those darn airplanes.

http://speedtalk.com/forum/viewtopi...er=asc&start=15

Thanks for the heads up.

I see no "hole". I see "poorly controlled" milling and grooves that appear to be much wider and inconsistent than the grooves that Singh and AB are advocating. These grooves converge at the spark plug relief notch.

I can't imagine that if there were a "hole" through the piston that the engine builder would allow a picture of it to appear without acknowledgement.

I still think the sharp edged domes need contoured.

Half way down that page that piston was clearly eating itself up.

Here are a few opinions on the BES engine masters entry. Looking at the pictures it is appears the modifications were done with out recommendations from Somender Singh. Everything I have read from Singh indicates cylinder head modifications, he has reasons for this. In addition squish clearance recommendations were not followed.

The engine builder reported a mistake that was made in the final compression ratio for the fuel in use. The poor valve angle of the Brodix heads required a dome piston to fill the large chamber; this in itself is not desirable for detonation resistance and superior flame speed. The burn patterns indicated incomplete combustion.

“The compression ratio was pretty stout at 12.5:1, and that may have been pushing it” Bischoff disclosed, “It may have been a mistake.”

It appears the engine builder attempted to compensate for detonation limitations with the tune up, adding fuel and retarding ignition timing on a detonation limited entry. The quote below indicated that the builder did not fully test the modifications before competition.

“The fire slots on the pistons were something Tony had little previous experience with, at least that he would admit to”