Is a .050" quench height still effective?

Posted By: BradH

Is a .050" quench height still effective? - 12/13/10 02:58 PM

Looking into how I can tweak (lower) the CR a tad and one option is to run a .050" head gasket vs. the standard .040". If I open up the quench to .050", is it still going to be effective?

Posted By: JohnRR

Re: Is a .050" quench height still effective? - 12/13/10 03:05 PM

Posted By: supercomp

Re: Is a .050" quench height still effective? - 12/13/10 03:25 PM

Better be, can't run any less with aluminum rods.

Posted By: BradH

Re: Is a .050" quench height still effective? - 12/13/10 04:10 PM

FWIW, mine is a steel-rod application.

Posted By: ademon

Re: Is a .050" quench height still effective? - 12/13/10 04:18 PM

How much difference is a .010 thicker gasket going to make in CR??? The tighter the quench the cooler the charge, If your having detonation/pinging you might be better off backing off the timing a couple degrees.

Posted By: BradH

Re: Is a .050" quench height still effective? - 12/13/10 04:31 PM

Between using a thicker gasket and choosing a gasket w/a larger ID (e.g. 4.45 or 4.50 vs. 4.38), I can "adjust" the CR down about .2 (from 11.0 to 10.8).

The concern is the cranking pressure w/ 11.0 and the cam on hand could be pushing it w/ the available pump gas octane (93), so I'm considering ways to address this w/o actually taking a step backward.

Posted By: ademon

Re: Is a .050" quench height still effective? - 12/13/10 04:52 PM

I'm running about 205 cranking psi on 93, But i run ram air, no heat crossover, very cold plugs, hi stall in lighter car and keep total timing at 30.

Posted By: dannysbee

Re: Is a .050" quench height still effective? - 12/13/10 04:55 PM

I would rather have the tighter quench with 11.00 to one than the .050 with 10.8 to one. I ran a 10.8 to one cast iron head with .038 with a .223 at 50 cam for years on 92 pump gas. Only time I had any problem was when the temp got in the high 90's. You would hear just a little in high gear. Couple gallons of race gas would fix it. With aluminum heads better combustion chamber shape and more cam duration I would think you would be OK.

Posted By: Darryls-Demon

Re: Is a .050" quench height still effective? - 12/13/10 05:26 PM

My 440 is 11:1 and I run 91 octane. The cylinder pressure is 170 PSI, the pistons are .005 out of the hole with a .039 gasket.
Also the tops of my pistons are thermo coated as are the cumbustion chambers, valves, intake and exhaust ports and the inside and out side of the intake manifold.

Posted By: 440Jim

Re: Is a .050" quench height still effective? - 12/13/10 05:31 PM

I don't have any data, but my feeling is that what you reduce the octane requirement by with the lower the CR, you will gain back with "less" quench. I don't think the quench is on/off, but more gradual change to the engine's octane requirement. So I wouldn't do that change in an attempt to need less octane fuel.

Posted By: maximum entropy

Re: Is a .050" quench height still effective? - 12/13/10 05:45 PM

i know how much you value my input (

), so i urge you to keep that quench as tight as possible! i've built several hot street engines with compression ratios close to 11:1, with very good results, as long as the quench is super tight. they've all been between .035 and .039. my personal mill started at .055, and had some issues in hot weather, that were completely ameliorated when i brought it to zero deck. i am the quench nazi because of this experience.

Posted By: sshemi

Re: Is a .050" quench height still effective? - 12/13/10 06:09 PM

just use a bad battery and a slow starter when checking crank comp and the pressure will decrease.
Problem solved.

Posted By: moparniac

Re: Is a .050" quench height still effective? - 12/13/10 06:13 PM

I raced on 93 pumpgas with more quench than that at 11 to 1

Posted By: sshemi

Re: Is a .050" quench height still effective? - 12/13/10 06:41 PM

Quote:

i know how much you value my input ( ), so i urge you to keep that quench as tight as possible! i've built several hot street engines with compression ratios close to 11:1, with very good results, as long as the quench is super tight. they've all been between .035 and .039. my personal mill started at .055, and had some issues in hot weather, that were completely ameliorated when i brought it to zero deck. i am the quench nazi because of this experience.

Was that the only change you did???

Posted By: 1_WILD_RT

Re: Is a .050" quench height still effective? - 12/13/10 06:46 PM

As others have stated tighter is better, your better choice is probably to use a thinner gasket, raise the compression but tighten the quench down to the low .03 range...

Posted By: Streetwize

Re: Is a .050" quench height still effective? - 12/13/10 07:00 PM

I shoot for and have seen the best results at a target of .040, I've run as tight as .036" on a 12:1 combo; To my mind you alsos have to be mindful about piston rock and remember the rock at TDC effects the quench area oppositely on each bank of a V8. I would consider anything above ~.045" the same as "no quench" and this applies only to steel rod combos.

Posted By: BradH

Re: Is a .050" quench height still effective? - 12/13/10 08:19 PM

I'm seeing a pattern here...

FWIW, the pistons stick out of the deck .002", so quench will be .038" w/ a typical composition gasket.

I haven't assembled the thing, yet. However, I've collected most of the parts already. I don't know if I'll have to band-aid the 11.0 CR w/ a longer duration cam or not at this point.

Posted By: maximum entropy

Re: Is a .050" quench height still effective? - 12/13/10 08:40 PM

Quote:

Quote:

i know how much you value my input ( ), so i urge you to keep that quench as tight as possible! i've built several hot street engines with compression ratios close to 11:1, with very good results, as long as the quench is super tight. they've all been between .035 and .039. my personal mill started at .055, and had some issues in hot weather, that were completely ameliorated when i brought it to zero deck. i am the quench nazi because of this experience.

Was that the only change you did???

i put in a slightly smaller cam, which would have made the problem worse. i hoped that the improved quench would help the situation (not that it was that bad), and to my surprise, the hot weather pinging has vanished. the car is faster, too btw. 1/2 a tenth.

Posted By: moparniac

Re: Is a .050" quench height still effective? - 12/13/10 10:24 PM

Quote:

I don't know if I'll have to band-aid the 11.0 CR w/ a longer duration cam or not at this point.

I also was at 11.12 to 1 in my challenger and I raced on 93 pump gas with that also! with a puny 248/254 @ 50 roller with more than .050 quench.... however The cam was 69 Intake valve closing ABDC..... ever wonder why wallace wants to know this on his dynamic calc? the higher the number the more its bleeds of cylinder pressure...

Ive seen miller post about this a few times also! good luck man

http://www.wallaceracing.com/dynamic-cr.php

Posted By: 602heavy

Re: Is a .050" quench height still effective? - 12/14/10 12:16 AM

Quote:

Quote:

I don't know if I'll have to band-aid the 11.0 CR w/ a longer duration cam or not at this point.

I also was at 11.12 to 1 in my challenger and I raced on 93 pump gas with that also! with a puny 248/254 @ 50 roller with more than .050 quench.... however The cam was 69 Intake valve closing ABDC..... ever wonder why wallace wants to know this on his dynamic calc? the higher the number the more its bleeds of cylinder pressure...

Does early intake valve closure have a direct bearing regards detonation? , maybe excessive overlap (ex bias) has more influence than we think..

, lots of variables to think about regards valve events.

Posted By: dOrk !

Re: Is a .050" quench height still effective? - 12/14/10 12:36 AM

50 is better than some of the stuff Ma Mopar has come out with .. !!

EVEN the 6 BBL engine .. look at that.

THEN the lowly 400 engine.... as far from GOOD quench as possible.

Posted By: Sport440

Re: Is a .050" quench height still effective? - 12/14/10 04:44 AM

Quote:

I'm seeing a pattern here...

FWIW, the pistons stick out of the deck .002", so quench will be .038" w/ a typical composition gasket.

Maintain your quench and use other methods if need be to lower comp.

Chamfer the bores around the intake valve at the block and the head, if need be.

As far as the effective perimiters of quench,

Is it incremental or is it on/off

KB pistons engineer John Erb implies its off after .060

I think its a little bit of both, But from the words of a old Engine guru,

"If your building from scratch, make maximizing the quench your number One priority toward achieving compression and avoiding Detonation"

mike