[BRUTAL64]

Originally Posted by 94cobra69ss396

Here's some info on quench from United Engine and Machine's website.

"Excessive cylinder pressure will encourage engine destroying detonation, and no piston is immune to its effects. An important first step is to set the assembled quench ("squish") distance to .040". The quench distance is the compressed thickness of the head gasket plus the deck clearance (the distance your piston is down in the bore). If your piston compression height (not dome height) is above the block deck, subtract the overage from the gasket thickness to get a true assembled quench distance. The quench area is the flat part of this piston that would contact a similar flat area on the cylinder head if you have zero assembled quench height. In a running engine the .040" quench usually decreases with RPM to a close collision between the piston and cylinder head. The shock wave from the close collision drives air at high velocity across the combustion chamber. This movement tends to cool hot spots, average the chamber temperature, and speeds flame travel after TDC to increase power. On the exhaust cycle, some cooling of this piston occurs due to the closeness of the hopefully cooler cylinder head. The power increase occurs because the shock wave occurs at exactly TDC on all cylinders, every time. It tends to make all cylinders alike and receive more identical flame travel speed. Spark scatter tends to be averaged with the TDC kick received from a tight quench.

Some non-quench engines, such as '68 and later Chrysler V-8's, can be converted to quench type with pistons such as the KB278, KB280, KB372, and KB373. Most Mopar cylinder heads recess the quench area into the head, so a raised area on the piston is necessary to get the close collision. If you are building an engine with steel rods, tight bearings and pistons, modest RPM, and automatic transmission, a .035" quench is the minimum practical to run without engine damage. The closer the piston comes to the cylinder head at operating speed, the more turbulence is generated. Unfortunately, the operating quench height varies in an engine as RPM and temperatures change. If aluminum rods, loose pistons (they rock and hit the head), and over 6000 RPM operation is anticipated, a static clearance of .055" could be required. A running quench height in excess of .060" will forfeit most of the benefits of the quench head design and can push the engine into severe detonation.

The suggested .040" static quench height is recommended as a good average dimension for stock rod engines up to 6500 RPM. Above 6500 RPM, rod selection becomes important. Since it is the close collision between the piston and the cylinder head that reduces the prospect of detonation, never add a shim or thick head gasket to lower compression on a quench head engine. If you have 10:1 with a proper quench and then add an extra .040" gasket to give 9.5:1 and .080" quench, you will likely create more ping at 9.5:l than you had at 10:1. One way to cheat the system is to make sure the piston of choice is light on quench side and to make sure the piston of choice is light on quench side and heavy on spark plug side. As RPM increases the piston tries to cock away from quench surface, allowing a tighter quench at most all RPM. The suitable way to lower the compression is to use a KB Dish Piston. KB Dish Pistons (reverse combustion chamber) are desinged for maximum quench area. Having part of the combustion chamber in the piston can improve the shape of the chamber and flame travel. The Step Dish is sort of an upscale version of our reqular configuration. It allows some piston weight reduction and allows the quench action to travel further across the chamber. It is especially favored when large dish cc's are required."

Some good info there.

[enkeivette]

...I'll pull out my plugs and measure the gaps to see if they've opened up at all in the last couple of months.

[94cobra69ss396]

Originally Posted by enkeivette

...I'll pull out my plugs and measure the gaps to see if they've opened up at all in the last couple of months.

Look for white specs in the plugs. That's a sign of detonation.

Check out this article with pictures http://www.stockcarracing.com/techar...ugs/index.html

[94cobra69ss396]

Here's a good article on quench for a SBC. http://www.chevyhiperformance.com/te...ide/index.html

[enkeivette]

Originally Posted by 94cobra69ss396

Look for white specs in the plugs. That's a sign of detonation.

Check out this article with pictures http://www.stockcarracing.com/techar...ugs/index.html

Will do.

My plug was cracked when I blew the piston, in just the one cylinder. And that was the first time I got on it fully after sealing it up. Those intake manifold gaskets had a short life.

That's why this time I didn't get on it fully till I got my WOT AFR into the 12s.



But back to Ben, post your piston to deck height and your compressed HG thickness. If you don't know them... you might be SOL. Unless you can find the HGs in some build list and the pistons are stock. Stock piston to deck should be an easy find for an LS1.

[BRUTAL64]

Originally Posted by 94cobra69ss396

Here's a good article on quench for a SBC. http://www.chevyhiperformance.com/te...ide/index.html

Every one should read this.


I wish the people I talk to at work were as smart as you guys. You people are a pleasure to share info with.

[enkeivette]

Originally Posted by 94cobra69ss396

Here's a good article on quench for a SBC. http://www.chevyhiperformance.com/te...ide/index.html

That artcile says not to run any tighter than .05 from a pro engine builder!!!

"According to Ken Duttweiler, the tightest quench he recommends is around 0.050-inch."

I wonder how much is really known about quench. When I called AFR and FelPro with my quench vs. compression questions, they both told me to go with the thicker HG. AFR's opinion was basically that yeah quench matters, but having proper compression is way more important. But once again, in a boosted app.

[BRUTAL64]

Originally Posted by enkeivette

That artcile says not to run any tighter than .05 from a pro engine builder!!!

"According to Ken Duttweiler, the tightest quench he recommends is around 0.050-inch."

I wonder how much is really known about quench. When I called AFR and FelPro with my quench vs. compression questions, they both told me to go with the thicker HG. AFR's opinion was basically that yeah quench matters, but having proper compression is way more important. But once again, in a boosted app.

So, look at it this way. A pro builder is looking at much higher rpms than the average Joe. My 400 is set up with .054 quench--cause I was always spinning them over 7000 rpm. So rod material, rpm and piston clearance set the final closest quench spec.


So a low rpm engine with close piston clearances could go .035 quench with a steel forged rod.

[Damian]

Originally Posted by Vettezuki

ODBII. I ordered some cheapy copper colder plugs.

I might be able to use my Tactrix cable and datalog and see whats going on.

[enkeivette]

Looks like it was actually Cometic that I talked to. Searched for my old thread. All of the gurus said that with boosted apps it is not important at all.

Not sure about NA.

Originally Posted by af2

You should have added, in a blown application. It is a different world than N/A.
Cometic is correct.

A 3100 lb car 6-71 blown 327 was built 20+ years ago with the piston .125 down the hole and still runs 11.0 quarter. Uses no oil and is driven most the time on the street. I agree it is not the best squish but the timing works well with this one. The rings are the Old TRW plasma ceramic! I wish they still made them!!!!

Originally Posted by Ron C.

It's not unusal to get conflicting tech info from different companies on the same item. I've even seen it within the same company. It boils down to who you are talking too at these companies.

For your application (blower) the .071 Cometic will work for you.
PS..I run a F3R.

Blessings.........Ron.

Originally Posted by Jason Pettis

All of the serious effort boosted engines we've done use (and will continue to use) dished pistons with basically no "quench" at all, and some have very thick head gaskets also. You wont have anything to worry about using a thick head gasket.

Jason

Originally Posted by CARRITAS RACING ENGINES

Cometic is right we have done it many times go for it.

Originally Posted by bigjoe1

With a blower, it is NOT important at all.PERIOD