Optimal Quench or DCR???
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From: Kannapolis, NC
Optimal Quench or DCR??? OK guys, I finally have hard numbers to play with. What are your opinions?
.005 out of hole
257.2 @ 50
266 @ 50
iopen 18.6 btdc
iclose 58.6 abdc
eopen 63
ex close 23
110 lsa
110 icl
.056 compressed gasket (GM)
I come up with a DCR of 8.4.1 and SCR of 11.3.1 Quench is not great at .051
However, Cometic has nothing but a .051 compressed gasket and for $100 more I did not feel it was worth it. If i went with the Cometic .051 I come up with 11.4 SCR and 8.491 DCR and a Quench of .046. This is on a 427ci NA motor. Let me hear what you guys think. I was told by the builder to just leave at 8.4 with factory gaskets as HP would only be a minimal loss (5-7) and it would be a safer bet on pump gas with no issues of detonation in extreme heat. Thanks for the opinions.
.
.005 out of hole
257.2 @ 50
266 @ 50
iopen 18.6 btdc
iclose 58.6 abdc
eopen 63
ex close 23
110 lsa
110 icl
.056 compressed gasket (GM)
I come up with a DCR of 8.4.1 and SCR of 11.3.1 Quench is not great at .051
However, Cometic has nothing but a .051 compressed gasket and for $100 more I did not feel it was worth it. If i went with the Cometic .051 I come up with 11.4 SCR and 8.491 DCR and a Quench of .046. This is on a 427ci NA motor. Let me hear what you guys think. I was told by the builder to just leave at 8.4 with factory gaskets as HP would only be a minimal loss (5-7) and it would be a safer bet on pump gas with no issues of detonation in extreme heat. Thanks for the opinions.
.
Last edited by 03 BUSA; Jan 2, 2007 at 06:51 PM.
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From: San Diego
Originally Posted by 03 BUSA
Hey guys, with some numbers I have been given I will have a DCR of 8.4.1 with a quench of around .044. using MLS GM LS7 gaskets. Would you stay with this setup to be in the safe DCR zone or go to a .040 gasket and have a DCR of around 8.6.1 but a quench of around .032? Car is NA on pump gas, weekend toy. Right now it is one of those deals raise DCR but get good quench or keep low DCR but not optimal quench. Thanks for the unput.
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Your at almost 42 deg overlap @ .050, even at a DCR of 8.4 I think you may run into a midrange cylinder pressure issue. You are gonna have to keep that engine very cool for it to work on pump gas. This is just a suggestion, I know I'm gonna get alot of jeers for saying this, but you might want to consider retarding the cam a few, say back to 112 or 113 ICL to kill some of the DCR, it will idle alot worse though, and you will lose some low end. That's my 2 cents.
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From: Kannapolis, NC
Originally Posted by GOaT Cheese
Your at almost 42 deg overlap @ .050, even at a DCR of 8.4 I think you may run into a midrange cylinder pressure issue. You are gonna have to keep that engine very cool for it to work on pump gas. This is just a suggestion, I know I'm gonna get alot of jeers for saying this, but you might want to consider retarding the cam a few, say back to 112 or 113 ICL to kill some of the DCR, it will idle alot worse though, and you will lose some low end. That's my 2 cents.
So you definitley would not go to a thinner gasket for quench? What are the issues I am faced with the midrange cyl pressure? Also, besides a 160 thermostat would you recommend I change from the TR55 to the TR6. Thanks for the help.
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From: San Diego
Originally Posted by 03 BUSA
So you definitley would not go to a thinner gasket for quench? What are the issues I am faced with the midrange cyl pressure? Also, besides a 160 thermostat would you recommend I change from the TR55 to the TR6. Thanks for the help.
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From: Kannapolis, NC
Originally Posted by GOaT Cheese
I wouldn't, you are already at +.005 on the deck, and acounting for the standard .025 for piston/rod "stretch", you only have .026 left for gitchy room with a .051 gasket.Going any thinner on the head gasket would make me real nervous. And at 42 deg overlap I think the midrange scavanging, assuming you have a bitchen exhaust system, is gonna pull in some serious air charge. I think you may have some detonation at around 4500 and up. Unless you can keep it around 180 degrees or so.
I am going Kooks 1/78 with no step no emmissions off road y-pipe and an open Borla catback. Again, I really appreciate your help. You seem to know alot about this issue. I would grade myself a mid level of this knowledge but no expert by any means.
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I would go thinner on the head gasket, the tighter the quench the less chance of detonation. If your pistons are .005 out of the hole, I would run an .040 gasket. That would give you a .035 quench. On my 402 my pistons are .011 out and I am running an .040 gasket which gives a .029 quench with no problems at all.
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From: Kannapolis, NC
Originally Posted by speedracer5532
I would go thinner on the head gasket, the tighter the quench the less chance of detonation. If your pistons are .005 out of the hole, I would run an .040 gasket. That would give you a .035 quench. On my 402 my pistons are .011 out and I am running an .040 gasket which gives a .029 quench with no problems at all.
I cannot run a .040 gasket the DCR would sky rocket into the 8.9.1 range, which optimal quench or not it would detonate in hot weather. The .045 Cometic would be around 8.79.1 which is still very high.
Originally Posted by DONAIMIAN
Id go with the thinner gasket (tighter quench) and play around with the cam to get you DCR to where you want it.
Originally Posted by 03 BUSA
I cannot run a .040 gasket the DCR would sky rocket into the 8.9.1 range, which optimal quench or not it would detonate in hot weather. The .045 Cometic would be around 8.79.1 which is still very high.
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From: San Diego
Originally Posted by speedracer5532
Instead on installing the cam straight up, advance the cam 2 or more degrees and that will lower your DCR. I think it is more important to have the tightest quench as possible than to have a lower DCR. 8.5 to 9.0 is optimal for DCR.
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From: San Diego
Originally Posted by Adrenaline_Z
What if the IVC is tuned for the application?
Why not alter piston volume, or chamber volume and have the quench height you desire?
Why not alter piston volume, or chamber volume and have the quench height you desire?
First off, you want the tightest quench you can reliably get.
Secondly, I highly doubt you have anything close to 8.4:1 DCR with that late of an intake valve closing point. What are the numbers at .006? That's what counts.
Secondly, I highly doubt you have anything close to 8.4:1 DCR with that late of an intake valve closing point. What are the numbers at .006? That's what counts.
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2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
