quench is quench

bsfc9 · Post by **bsfc9** » Fri Apr 22, 2005 1:28 pm

Does it matter how one achieves total quench? If I want to run a total of, let's say, .040--I can put the piston in the hole .013 and use a .027 head gasket or I could run zero deck and a .040 gasket. Does it matter?

shawn · Post by **shawn** » Fri Apr 22, 2005 1:45 pm

I've always been a fan of leaving the piston in the hole a little and using a thinner gasket. This leaves some of the block for cleanup later, and the thin gaskets seem to distort the block less.It also gives you more options for setting that quench height by varying the gasket thickness.
shawn

bill jones · Post by **bill jones** » Fri Apr 22, 2005 3:21 pm

-I think there is definetly something to the heat transfer thru the head gasket.
-If you had zero deck and the option of using a copper gasket versus a fabric gasket, the copper will transfer the heat big time compared to the fabric gasket.
-Other than that I don't see where it matters as to how you end up with the deck clearance.

panic · Post by **panic** » Fri Apr 22, 2005 5:08 pm

Harley-Davidson found that pop-up with the quench relief all inside the chamber was a slight improvement, probably caused by the escaping intake charge being aimed straight across at the plug.

Trev · Post by **Trev** » Fri Apr 22, 2005 9:54 pm

I cant see that it really matters either way
If you have a 38 thou quench

10 down the bore and a 28 thou head gasket, or

zero and a 38 thou head gasket.

The real factor in either is the top of the piston is still 38 thou from the head surface and your quench area is exactly the same.

I think more important is just getting the correct quench area

My 2 cents worth
Trev

Post by **gofaster** » Sat Apr 23, 2005 3:09 am

On Harleys I like to run an angled dome and machine the complement out of the head. On a single squish Evo I like to put a 30 degree cut in the D shelf, and match it with a 30 degree dome that nests in the D and tapers over to the deck on the other side.
On aftermarket bathtub heads, Evo Sportsters, Buells, and Twincams that have a more symmetrical chamber I like to run an angle dome of 10 to 30 degrees and shave the crown straight across to get the needed compression ratio. I keep the squish clearance between .030 and .040.
For guys on a budget I've turned down the head gasket surface of the head to bring the D closer to the piston, or used those slick gaskets that Hansen and Cometic were offering that came in varying thicknesses. I haven't been able to get my hands on them for a while. Probably need to make a few phone calls when I get the time.....

68corvette · Post by **68corvette** » Sat Apr 23, 2005 4:40 am

I have been thinkin how similar "harley like" setup would work in sbc..
If combustion chamber would be very high and quench area would be angled to some degree, would that increase squish effect because of increased quench area / increased turbulance speeds?

when lookin those nascar and engine master engines they are trying to get lot of quench.

Some motorcycles are using clover shaped combustion chambers to gain more quenc into combustion chamber.

Anybody tried?

SStrokerAce · Post by **SStrokerAce** » Sat Apr 23, 2005 5:01 pm

Lots of quench and a chamber that's not as wide as it is tall..... Or in other words a chamber that is partly in the piston and partly in the head and is shaped more like a sphere with the plug in the center of it. When you see the amount of timing that Kaases Engine Masters motors use or a Cup motor it's pretty impressive. 24-26 deg total to get the job done.

I always think of it this way..... what's going to burn faster given the same amount of volume:

1. a sphere with the ignition in the middle of the sphere so the flame can start burning and go out from there in all directions

2. a pancake with the ignition starting on one side of the pancake and having to travel all the way across the volume from one side to another.

Or think about that big box of mouse traps with ping pong balls on them.... you can either drop a ball on one of the traps on the edge to start the reaction or in the center.....

Bret

headman · Post by **headman** » Sun Apr 24, 2005 10:09 am

SStrokerAce wrote:
1. a sphere with the ignition in the middle of the sphere so the flame can start burning and go out from there in all directions

2. a pancake with the ignition starting on one side of the pancake and having to travel all the way across the volume from one side to another.

Or think about that big box of mouse traps with ping pong balls on them.... you can either drop a ball on one of the traps on the edge to start the reaction or in the center.....

Bret

At first glance the spherical chamber seems the obvious solution.

Food for thought:
If the "pancake" is promoting a more homogeneous charge, or a more conducive enviroment for combustion; then these merits may spread the burn more violently and completely than the simple proximity of the spark inside the sphere.

However, I agree the "sphere" is the intuitive solution.

SStrokerAce · Post by **SStrokerAce** » Sun Apr 24, 2005 7:04 pm

headman....

That's a interesting thought.... obvously the quality of the mixture comes into play as well.

That goes into something else.... bore sizes. I've heard that bore sizes over 4.500" are hard to produce a good burn in with one plug. Adding lots of quench to that application would help out a ton.

Bret

68corvette · Post by **68corvette** » Mon Apr 25, 2005 7:54 am

here is what i mentioned:
http://www.imagezs.com/member/pic.php?u ... inI&i=8380

SWB · Post by **SWB** » Mon Apr 25, 2005 12:35 pm

AAA
| | |

That's almost like what we're doing with a head I'm working on right now.

I'm not so sure it's the best way, but I'm keeping my mind open and trying to get a handle on the possibilities and how we can improve things as we go. My experience with squish area so far has been the more the merrier and the tighter (without things touching) the better. With that philosophy we've been running as little as 28 degrees advance for best power in some cases and if I can lessen that even more, I'll be happy.

SWB

MKF · Post by **MKF** » Mon Apr 25, 2005 1:34 pm

I'm freshening an engine that originally had the piston .020 in the hole. The deck surfaces were milled .028 to remove O-ring grooves which now leaves the piston .008 above the deck. The plan was to use A.070 Cometic gasket which would yield a .062 quench dimension, which was very close to the original .060 dimension that was achieved by a .040 head gasket and the piston .020 in the hole. I've been concerned that this might negatively impact the performance but I'm not sure. Any thoughts or experiences would be appreciated. The engine is a BBC
4.625 bore, 4.500 stroke with 14 degree Big Chiefs.

Len · Post by **Len** » Mon Apr 25, 2005 10:27 pm

I would think that if you had 50% of the combustion chamber in the head and 50% in the piston with as much quench area as possible on a wedge type combustion chamber with the outline of the dish a mirror image of the chamber and the dish itself very much like a rounded cup with approx 45 degree slopes that it would be the most efficient. I am hoping to try that out on my new engine.
Len

gas · Post by **gas** » Sat Jun 04, 2005 6:27 pm

SStrokerAce wrote:1. a sphere with the ignition in the middle of the sphere so the flame can start burning and go out from there in all directions.

headman wrote:However, I agree the "sphere" is the intuitive solution.

If that were the case, you'd think you'd see one in use (competitively) in race environment.

Gary

Don Terrill’s Speed-Talk

quench is quench

quench is quench

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quench is quench