Advice on compression, detonation, and quench
#2042394
03/31/16 12:13 AM
03/31/16 12:13 AM
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Joined: Feb 2006
Posts: 267 New Jersey
69Chrgr
OP
enthusiast
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OP
enthusiast
Joined: Feb 2006
Posts: 267
New Jersey
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Getting ready to install the heads on my 440 and looking for advice here is the build 2355 flat top pistons .015 deck clearance 915 big valve ported heads 75cc chambers 284 484 68 degree overlap purple cam installed @ 108
With a .039 gasket it comes to 10.6 With a .051 it's 10.4 With a .060 it's 10.17
For what I'm reading the only chance of quench will be with the .039 head gasket,and that lowering the compression with the thicker gasket may make it ping more by losing the quench,I want to be able to run 93 ultra without cranking back the timing a bunch. I went with the original 484 to kill some cylinder pressure. Is this combo gonna be a problem to keep from pinging? Looking for some thoughts and experience on this
Thanks
Duane
Last edited by 69Chrgr; 03/31/16 12:16 AM.
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Re: Advice on compression, detonation, and quench
[Re: 69Chrgr]
#2042446
03/31/16 01:37 AM
03/31/16 01:37 AM
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Joined: Nov 2003
Posts: 36,040 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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I'd want a bit tighter quench & take some CC's out of the heads. HG thicknesses can vary a fair amt from the published specs. 10's seems a bit high for iron heads/marginal (mike the gaskets) quench. As you mentioned you do not wanna have to compromise the curve. One of our left coast members went thru a nightmare with that (SCR too high)
live every 24 hour block of time like it's your last day on earth
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Re: Advice on compression, detonation, and quench
[Re: 69Chrgr]
#2042479
03/31/16 02:39 AM
03/31/16 02:39 AM
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Joined: May 2008
Posts: 5,399 Aurora, Colorado
451Mopar
master
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master
Joined: May 2008
Posts: 5,399
Aurora, Colorado
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I'd try the 0.039" gaskets, but run a 160-degree thermostat and anything to lower the air inlet temperature like a hood scoop, phenolic carb spacer and such. Compressing the air/fuel mixture increases its temperature, so anything to lower the inlet temps will help reduce pre-ignition. You could also switch to E-85, 105 octane and dumping in 25% more fuel helps cool things down.
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Re: Advice on compression, detonation, and quench
[Re: dizuster]
#2042750
03/31/16 03:27 PM
03/31/16 03:27 PM
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Joined: Nov 2007
Posts: 21,825 Kirkland, Washington
Pacnorthcuda
Too Many Posts
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Kirkland, Washington
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I agree, I'd consider actually taking another .015" off the deck. It will bring the compression up to 11:1'ish, but with the tighter quench will give you a better chance at pump gas...
I ran a small block at .030" quench at 12.2:1 on pump. Get the 440 up around .040" quench and 11:1 with that much cam and you'll be ok.
Worse case you have to take a couple of degree's of timing out of it. It would be easier to just use Cometic .027 gaskets but I don't think he would get away with 11:1 Iron heads on 93. To the OP--do you know your cam's intake closing degree BTDC?
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Re: Advice on compression, detonation, and quench
[Re: Adam71Charger]
#2042797
03/31/16 04:54 PM
03/31/16 04:54 PM
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Joined: May 2008
Posts: 5,399 Aurora, Colorado
451Mopar
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master
Joined: May 2008
Posts: 5,399
Aurora, Colorado
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Green horn input here, but if his quench is good, doesnt dynamic compression ratio have more to do with detonation than static? Quench is not good, dynamic CR still high because cam is sort of small for the static compression ratio, Stock iron heads and spark plug location at edge of chamber doesn't help either. If it were me, I would zero deck the block for quench and toss some RPM heads on it, but I think he wants to use the iron heads? It sounds like he has some time and $$$ into them?
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Re: Advice on compression, detonation, and quench
[Re: Adam71Charger]
#2042798
03/31/16 04:54 PM
03/31/16 04:54 PM
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Joined: Feb 2003
Posts: 21,318 Manitoba, Canada
DaytonaTurbo
Too Many Posts
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Too Many Posts
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Posts: 21,318
Manitoba, Canada
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Green horn input here, but if his quench is good, doesnt dynamic compression ratio have more to do with detonation than static? Only in the sense that good quench will let your engine tolerate more SCR and DCR. Either way, OP is going to be on the razor's edge for pump gas.
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Re: Advice on compression, detonation, and quench
[Re: 69Chrgr]
#2043005
03/31/16 09:52 PM
03/31/16 09:52 PM
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Joined: Feb 2005
Posts: 4,314 Prospect, PA
BSB67
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Prospect, PA
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Sorry to tell you this, but it is highly unlikely what you have now will work at your elevation. I've done the 915 head in the 10s for CR and there is no quench/phenolic spacer/cold thermostat/cold plug, cold manifold /slow curve/loose converter/tall gear that will fix the problem.
I had a friend in your situation just have a portion his 2355s milled with a step to reduce the CR but kept the quench. Ran pretty good.
If you want to try one of the options listed, the 0.060" gasket will be your best shot at getting it to work. You will not get better results by increasing the CR hoping the quench thing will help. You lose ground faster with the increased CR than help from the quench. Again, this is from experience.
Last edited by BSB67; 03/31/16 09:53 PM.
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Re: Advice on compression, detonation, and quench
[Re: 69Chrgr]
#2043184
04/01/16 12:00 AM
04/01/16 12:00 AM
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Joined: Jun 2003
Posts: 52,972 Romeo MI
MR_P_BODY
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Master
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Posts: 52,972
Romeo MI
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I'm running a 416 at 10.4 compression with a .039 compressed HG... this is iron W-2 heads... the cam is what counts... I'm running a 260/270 on a 105 LSA installed at 105.. I run it on the street on 87 octane with NO/NONE spark ping.. thats with a 180 stat... I am sure that with 10.6 on 93 octane you wont have a issue IF you have the right cam... my engine made 590hp on 93 octane with 40 degrees of timing on the dyno.. I run it at 38 degrees all the time on the street.. and will at the track EDIT My pistons are at zero deck... but I have a 22cc dish to give the compression.. if your pistons come up with that compression at zero deck I really dont think you will have any issue... I always try to get .040 quench
Last edited by MR_P_BODY; 04/01/16 12:11 AM.
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Re: Advice on compression, detonation, and quench
[Re: 69Chrgr]
#2043232
04/01/16 12:44 AM
04/01/16 12:44 AM
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Joined: Nov 2011
Posts: 2,154 Its a TRAP!
DARTH V8Я
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Oh No!! I just had a moron attack!
Joined: Nov 2011
Posts: 2,154
Its a TRAP!
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Smallest chamber possible (for your valve size) + D-dish pistons with a zero deck would be the way to go IMO.
When it takes more than a sweet mullet to prove you rule at the trailer park..
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