Quench - 1969 L36
08-10-2018, 06:34 PM
#1
Instructor
Thread Starter
Quench - 1969 L36
Hi Everyone,
I'm sure this has likely been discussed many times over - I'm just curious to know what the maximum amount of quench is acceptable in a 427. I've rebuilt the original L36 motor and the machinist has told me pistons are .015 in the hole. I was hoping to use the standard Fel-Pro blue head gasket with a compressed thickness of .039. This means I'd be sitting at .054 quench. I've read that anything above .060 will promote detonation. Just curious to know if running the blue Fel-Pro is going to create detonation problems for me. With that Fel-Pro in place my Compression ratio would be 10:1.
Appreciate the help!
I'm sure this has likely been discussed many times over - I'm just curious to know what the maximum amount of quench is acceptable in a 427. I've rebuilt the original L36 motor and the machinist has told me pistons are .015 in the hole. I was hoping to use the standard Fel-Pro blue head gasket with a compressed thickness of .039. This means I'd be sitting at .054 quench. I've read that anything above .060 will promote detonation. Just curious to know if running the blue Fel-Pro is going to create detonation problems for me. With that Fel-Pro in place my Compression ratio would be 10:1.
Appreciate the help!
08-10-2018, 06:51 PM
#2
Safety Car
.030 to .035is the ideal quench but your overall compression will dictate what fuel must be run. I think you are leaving a lot of power on the table with .058 but you may get away with running regular gas and super mix. So it’s a done deal unless you want to go with a thinner head gasket.
08-10-2018, 06:57 PM
#3
Instructor
Thread Starter
.030 to .035is the ideal quench but your overall compression will dictate what fuel must be run. I think you are leaving a lot of power on the table with .058 but you may get away with running regular gas and super mix. So it’s a done deal unless you want to go with a thinner head gasket.
08-10-2018, 09:53 PM
#4
Race Director
These are 100 to 106cc heads? Get the chambers opened up to 116 to 120. Bunch of meat on the intake valve side of the plug also restricts flow and power. You can always get 781 or 049 far cheaper, but I suspect you want orig.
Last edited by derekderek; 08-11-2018 at 08:26 AM.
08-11-2018, 12:06 PM
#5
Le Mans Master
Quench is a great way to get high compression and avoid detonation. Piston top design is also a factor. If just dish with no quench pad the effect will be minimal. Flat tops or D-dish is your best bet.
i run 10.6:1 with D-dish on 91 or 87 and no detonation.
distance ideally is in the .030 to .040 range. I run .038. Depends on your rpm limit and, piston rock and rod stretch as to how big that needs to be.
i run 10.6:1 with D-dish on 91 or 87 and no detonation.
distance ideally is in the .030 to .040 range. I run .038. Depends on your rpm limit and, piston rock and rod stretch as to how big that needs to be.
08-11-2018, 12:14 PM
#6
Race Director
That number is hard to reach with standard head gaskets without decking the block. I have a few OEM gen 6 head gaskets that are composite and .027 thick. I believe they work with Mark 4 heads and blocks. It is the MK4 gasket that doesn't work with later engines. I have to do some searching to find part number. Got it!! 14097000. Then called chebby. Discontinued... There are some to be found, but are disappearing. Sux...
Last edited by derekderek; 08-11-2018 at 12:38 PM.
08-11-2018, 02:09 PM
#8
Le Mans Master
Member Since: Oct 2002
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Good quench does help resist detonation but you need a good quench pad on the piston and should have at least 9:1 compression ratio to make it work. But did you know polishing the cylinder head chamber and removing sharp edges from the piston crown help prevent detonation also? Are you going to rework those to?
Myself I feel quench is overrated though it's something that can help performance. If motors would detonate w/o quench then all the stock engines would rapidly distruct. Think about it.
Myself I feel quench is overrated though it's something that can help performance. If motors would detonate w/o quench then all the stock engines would rapidly distruct. Think about it.
08-11-2018, 02:22 PM
#9
Le Mans Master
http://speedtalk.com/forum/viewtopic...rance&start=15
https://www.hotrod.com/articles/ideal-quench-height/
here is some reading on the subject.
https://www.hotrod.com/articles/ideal-quench-height/
here is some reading on the subject.
Last edited by REELAV8R; 08-11-2018 at 02:22 PM.
08-11-2018, 02:45 PM
#10
Le Mans Master
Here some more
http://www.superchevy.com/how-to/eng...earance-guide/
cardo I would have to disagree that the effect of squish is over rated. I have experienced both ends of the spectrum.
low CR on the stock motor of 7.6:1 and it rattled even on 91 octane at WOT and good tuning.
same motor 9.9:1 no detonation even at 86 octane but .038 squish.
now 10.6:1 still no deto, no matter the timing, I tried and all I got was a loss of power by advancing timing, but no deto.
http://www.superchevy.com/how-to/eng...earance-guide/
cardo I would have to disagree that the effect of squish is over rated. I have experienced both ends of the spectrum.
low CR on the stock motor of 7.6:1 and it rattled even on 91 octane at WOT and good tuning.
same motor 9.9:1 no detonation even at 86 octane but .038 squish.
now 10.6:1 still no deto, no matter the timing, I tried and all I got was a loss of power by advancing timing, but no deto.
08-11-2018, 02:48 PM
#11
Race Director
Especially just rounding off the sharp edges where machined deck meets cast chamber. That sharp edge can become a glow plug.
Last edited by derekderek; 08-11-2018 at 02:48 PM.
08-11-2018, 03:06 PM
#12
Le Mans Master
Member Since: Oct 2002
Location: Las Vegas - Just stop perpetuating myths please.
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Here some more
http://www.superchevy.com/how-to/eng...earance-guide/
cardo I would have to disagree that the effect of squish is over rated. I have experienced both ends of the spectrum.
low CR on the stock motor of 7.6:1 and it rattled even on 91 octane at WOT and good tuning.
same motor 9.9:1 no detonation even at 86 octane but .038 squish.
now 10.6:1 still no deto, no matter the timing, I tried and all I got was a loss of power by advancing timing, but no deto.
http://www.superchevy.com/how-to/eng...earance-guide/
cardo I would have to disagree that the effect of squish is over rated. I have experienced both ends of the spectrum.
low CR on the stock motor of 7.6:1 and it rattled even on 91 octane at WOT and good tuning.
same motor 9.9:1 no detonation even at 86 octane but .038 squish.
now 10.6:1 still no deto, no matter the timing, I tried and all I got was a loss of power by advancing timing, but no deto.
Sorry the Speed Talk thread was to wordy/lengthy to review.
08-12-2018, 12:41 AM
#13
Le Mans Master
Well I don't think you have an objective test there. An objective test would be the case where you only changed the quench height and nothing else. I expect you changed a lot of hardware and their configuration when you changed deck height for this. Even your Super Chevy article says: So what are the benefits of all this squishing and quenching? The benefits are small, but >> often important. Pump-gas engines that run on the ragged edge of detonation, for example, can greatly benefit from a tighter piston-to-head clearance to reduce rattle.
Sorry the Speed Talk thread was to wordy/lengthy to review.
Sorry the Speed Talk thread was to wordy/lengthy to review.
i had a yz250 2 stroke racing bike that detonated regardless of the fuel used up to 94 octane.
this was when I found out about the importance of quench distance. It took the cylinder head and had it shaved to reduce the quench from .060” to .040”.
nothing else changed on the bike, not even the plug. After the quench reduction I could run 91 octane even on the hottest days and experienced no detonation ever again.
08-12-2018, 12:26 PM
#14
Le Mans Master
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Location: Las Vegas - Just stop perpetuating myths please.
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Well congratulations and I'm glad to read of your success with that motor. But the point I'm trying to make is good quench height may not be as effective or effective at all. Just think about compression pressure. The lower the static compression the lower the compression pressure and the lower the sqwish effect - less initiating force. Many dished pistons have very little quench area if any quench area and quench height will make little or none difference. Sharp edges in the cylinder head chamber and on the piston crown can undo what a good quench height tries to do.
Yes good quench can make a difference and I would always try to include it in a motor build. But many times other circumstances like piston design defeat that effort. I would not build a motor with excessive static compression expecting a good quench height to compensate. Clean up the chambers, clean up the piston crowns and build with an appropriate dynamic compression ratio.
That's my 2 cents on quench.
Yes good quench can make a difference and I would always try to include it in a motor build. But many times other circumstances like piston design defeat that effort. I would not build a motor with excessive static compression expecting a good quench height to compensate. Clean up the chambers, clean up the piston crowns and build with an appropriate dynamic compression ratio.
That's my 2 cents on quench.
08-12-2018, 07:24 PM
#15
Le Mans Master
Well congratulations and I'm glad to read of your success with that motor. But the point I'm trying to make is good quench height may not be as effective or effective at all. Just think about compression pressure. The lower the static compression the lower the compression pressure and the lower the sqwish effect - less initiating force. Many dished pistons have very little quench area if any quench area and quench height will make little or none difference. Sharp edges in the cylinder head chamber and on the piston crown can undo what a good quench height tries to do.
Yes good quench can make a difference and I would always try to include it in a motor build. But many times other circumstances like piston design defeat that effort. I would not build a motor with excessive static compression expecting a good quench height to compensate. Clean up the chambers, clean up the piston crowns and build with an appropriate dynamic compression ratio.
That's my 2 cents on quench.
Yes good quench can make a difference and I would always try to include it in a motor build. But many times other circumstances like piston design defeat that effort. I would not build a motor with excessive static compression expecting a good quench height to compensate. Clean up the chambers, clean up the piston crowns and build with an appropriate dynamic compression ratio.
That's my 2 cents on quench.
except this portion.
The lower the static compression the lower the compression pressure and the lower the sqwish effect
Piston top design is critical to a good squish effect.
Agree on combustion chamber. I go so far as to polish mine to not only eliminate sharp points but to make the surface smoother (shiny smooth) in hopes of staving off carbon deposits.
Last edited by REELAV8R; 08-12-2018 at 07:26 PM.