Re: Head gasket thickness...how much would you go ?
[Re: X9 X3 R/T]
#2805631
08/06/20 03:15 AM
08/06/20 03:15 AM
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Joined: Aug 2011
Posts: 2,905 Pattison Texas
CSK
master
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master
Joined: Aug 2011
Posts: 2,905
Pattison Texas
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Mine is about the same. but its a 512 lowdeck, .016 above the deck I went with .051 Com gaskets, any closer would hit the head, I have run 10k miles & all is good
Last edited by csk; 08/06/20 03:17 AM.
1968 Charger COLD A/C Hilborn EFI 512ci 9.7 compression, Stealth heads, 4.10 gear A518 ODtrans 4100lb,10.93 full street car trim 2020 T/A 392 Stock 11.79 @ 114.5
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Re: Head gasket thickness...how much would you go ?
[Re: Stanton]
#2805670
08/06/20 09:19 AM
08/06/20 09:19 AM
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Joined: May 2019
Posts: 722 Lake Villa Il
INTMD8
super stock
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super stock
Joined: May 2019
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Lake Villa Il
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Tightest I've ran was an LS7 with .027 piston to head. Passenger side pistons showed signs of just touching the head at that point.
I like the .051 cometic idea.
69 Charger. 438ci Gen2 hemi. Flex fuel. Holley HP efi. 650rwhp @7250 510rwtq @5700
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Re: Head gasket thickness...how much would you go ?
[Re: X9 X3 R/T]
#2805697
08/06/20 10:58 AM
08/06/20 10:58 AM
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Joined: Oct 2007
Posts: 4,219 New York
polyspheric
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master
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New York
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I've read about quench as close as .025", but: 1. Tight piston to wall, small bore, and long rod ratios limit contact at TDC rock-over 2. How fast did the engine turn? 3. Did a leak-down test show the same results as with more clearance? The first damage to occur with only slightly too little is a slight collapse of the vertical clearance of the top ring groove, it may even be invisible but a feeler gauge will show below the usual .006". This restricts the ring's access to combustion pressure and reduces seal.
Anything less than .035" makes me nervous. Grumpy said 50 years ago that if you don't need that much anti-knock, you can reduce pumping loss by increasing it to .060". Pulling those CC in the quench band in & out constantly uses power, think of quickly separating 2 flat pieces of glass.
Boffin Emeritus
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Re: Head gasket thickness...how much would you go ?
[Re: polyspheric]
#2806325
08/07/20 09:39 PM
08/07/20 09:39 PM
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Joined: Jan 2003
Posts: 10,091 Frostbitefalls MN (Rocky&Bullw...
gregsdart
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 10,091
Frostbitefalls MN (Rocky&Bullw...
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You can take a thin cut off the pistons if you have a certain combo in mind. I had a set of pistons cut. .008 to get exactly what i wanted on a 408 stroker. Cost me $80.
8.582, 160.18 mph best, 2905 lbs 549, indy 572-13, alky
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Re: Head gasket thickness...how much would you go ?
[Re: X9 X3 R/T]
#2806355
08/07/20 10:39 PM
08/07/20 10:39 PM
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Joined: Aug 2011
Posts: 2,905 Pattison Texas
CSK
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master
Joined: Aug 2011
Posts: 2,905
Pattison Texas
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Has anyone used the .051 head gaskets that 440 source sells ? They are only $15 each and would work for a while. This car is never getting nitrous. It would give me enough room for the heads decent compression. I have not used them, but I have seen them, they look good, I would have no problem using them in your case, I had my surfaces done for the cometic gaskets,
1968 Charger COLD A/C Hilborn EFI 512ci 9.7 compression, Stealth heads, 4.10 gear A518 ODtrans 4100lb,10.93 full street car trim 2020 T/A 392 Stock 11.79 @ 114.5
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Re: Head gasket thickness...how much would you go ?
[Re: X9 X3 R/T]
#2807010
08/09/20 07:28 PM
08/09/20 07:28 PM
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Joined: May 2019
Posts: 722 Lake Villa Il
INTMD8
super stock
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super stock
Joined: May 2019
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Lake Villa Il
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If the surface looks like you would need copper coat to seal MLS I would not use them. JMO
69 Charger. 438ci Gen2 hemi. Flex fuel. Holley HP efi. 650rwhp @7250 510rwtq @5700
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Re: Head gasket thickness...how much would you go ?
[Re: INTMD8]
#2807013
08/09/20 07:32 PM
08/09/20 07:32 PM
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Joined: Aug 2011
Posts: 2,905 Pattison Texas
CSK
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master
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Pattison Texas
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If the surface looks like you would need copper coat to seal MLS I would not use them. JMO he is not using MLS, the 440 source are coated composition
1968 Charger COLD A/C Hilborn EFI 512ci 9.7 compression, Stealth heads, 4.10 gear A518 ODtrans 4100lb,10.93 full street car trim 2020 T/A 392 Stock 11.79 @ 114.5
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Re: Head gasket thickness...how much would you go ?
[Re: CSK]
#2807306
08/10/20 02:25 PM
08/10/20 02:25 PM
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Joined: Jan 2010
Posts: 1,443 NW Chicago suburban area
Mopar Mitch
pro stock
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pro stock
Joined: Jan 2010
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NW Chicago suburban area
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When I read posts or articles -- where ever, magazines, etc -- and they are leaning towards most concern about gasket thickness, they are missing the most important concern of all -- combustion seal.
Unless the head gasket is MLS, a composition design head gasket must have a durable combustion seal for the sake of defending itself against pre-ignition and detonation -- both of which will practically always exist in hi-performance race engines.
Wire ring combustion seals will act as a dam, fortress... against detonation and pre-ignition.... and that's what's needed with composition head gaskets for performance/race applications
IF you want to change CR, then change the pistons or change the cylinder head's chamber volume.
I'm a former gasket engineer from a major company.
Mopar Mitch
"Road racers and autocrossers go in deeper and come out harder!"... and rain never stops us from having fun with our cars... in fact, it makes us better drivers!
Check out MOPAR ACTION MAGAZINE, August 2006 issue for feature article and specs on my autocross T/A!
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Re: Head gasket thickness...how much would you go ?
[Re: Mopar Mitch]
#2807521
08/10/20 11:53 PM
08/10/20 11:53 PM
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Joined: Jan 2003
Posts: 6,163 Melbourne , Australia
LA360
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master
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Melbourne , Australia
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I have 0.051" Cometic head gaskets in my small block, as a means to gain some needed clearance. I can't for the life of me remember which year he ran it, but I remember Jon Kaase ran a MLS gasket that was around 0.060"-0.070" thick.
Alan Jones
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Re: Head gasket thickness...how much would you go ?
[Re: LA360]
#2807734
08/11/20 03:01 PM
08/11/20 03:01 PM
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Joined: Jan 2010
Posts: 1,443 NW Chicago suburban area
Mopar Mitch
pro stock
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pro stock
Joined: Jan 2010
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NW Chicago suburban area
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The main reason different head gasket thicknesses should be considered is to correct dimensional geometry of an assembled engine >> deck height. There are thin metal "spacer shims" (dead soft copper) also available from different sources.. to adjust the deck height after excessive and/or repeated resurfacing of the deck. Older engines are prime candidates for this usage. Similarly, that's the reason why gasket manufacturers have slightly increased their composition thicknesses of their head gaskets. In other words, the past common ~032-038" thicknesses, have become up to ~050-058... in that range.... strictly for geometry corrections to the block assembly for deck height.
Mopar Mitch
"Road racers and autocrossers go in deeper and come out harder!"... and rain never stops us from having fun with our cars... in fact, it makes us better drivers!
Check out MOPAR ACTION MAGAZINE, August 2006 issue for feature article and specs on my autocross T/A!
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