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Old 05-02-2012, 01:20 PM
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Importance of Quench

Hey guys and gals. I know this topic has been beat to death and I did research previous forums and threads on this subject before posting. My question is how crucial is quench in a daily driver and what factors make it more crucial such as vehicle weight, gearing,etc? Right now I'm working on building a motor mentioned in one of my previous post and am at the point where I need to make a head gasket selection. I already have a new set that is .040 and they claim it's .038 crushed, that would put me at an average of .058 quench which is a little high according to the majority which have ranged from .035 to .060. Truck is driven 72 miles a day five days a week. Here are my specs and thank you in advance.

1982 K10 Suburban
Weight 5600lbs. with me in it
3.73 gears w/31x10.5 tires
700r4 Trans
.060 over 350
Eagle forged rotating assembly
KB Pistons Flat tops with 2 valve releifs
Chevy Iron Heads 642's w/1.72intake and 1.5exhaust valves 76cc Chambers
Bowls and Throat on heads have been cleaned up and exhaust ports mirror finished
Estimated CR 9-9.5:1
Comp High Energy Cam 268 Flat tappet
Cast Manifold with 750 cfm Q-Jet
Upgraded HEI (MSD)
1 1/2" Full Length headers with 3" exhaust to muffler with 2 1/2" pipes out the back door.

The goal was decent power down low and mid range power with somewhat decent gas mileage if that was even possible with this tank using parts I already own. I know valves are small and hinder high range but I can't afford machining them so I gotta run with what I got. Thanks.

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Old 05-02-2012, 02:58 PM
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If you estimate .058 quench with that gasket, you assume the piston is .020 in the hole? If that is the case, your c.r. is 8.72:1. At .058 quench, you're not too bad off. The price of head gaskets is less than $30.00, if you went with a .015 (FelPro Q1094 HP gasket) it would put you on the other side of ideal quench. You sure your piston isn't .025 down?? Has the block been cut .005? If that is so, your c.r. is more like 8.64. JFYI.
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Old 05-02-2012, 04:20 PM
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Quote:
Originally Posted by 68NovaSS
If you estimate .058 quench with that gasket, you assume the piston is .020 in the hole? If that is the case, your c.r. is 8.72:1. At .058 quench, you're not too bad off. The price of head gaskets is less than $30.00, if you went with a .015 (FelPro Q1094 HP gasket) it would put you on the other side of ideal quench. You sure your piston isn't .025 down?? Has the block been cut .005? If that is so, your c.r. is more like 8.64. JFYI.
Thanks for responding. The block was decked, but it's been several years ago and I can't remember how much or even if they told me. I checked with a dial indicator and they ranged from .018 to .021 in the hole. The pistons are aftermarket and from experience I know they have roughly a +/- .002 clearance on their quality control for wrist pin location which could explain why I had that range. Just ran specs through summit's CR calculator and your right it came out to 8.74 static CR. Was hoping to be a little closer to 9:1 but not too far off. Your probably right and I should just go with the smaller gasket. I just was wondering how critical it is to overall performance it is to be in that lower range. Are there any negative effects to worry about being at .058? Either way I'd still like to bump up my CR a little which leans towards a smaller gasket I'm just a little worried running a .015 gasket on a .060 over 350, it never had heating issues but still concerns me. Thanks again.
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Old 05-02-2012, 06:47 PM
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You could run the GMMP .028" gasket and give you .046 quench. I'd stay on the tight side if it were me. My truck is similar, 355 268 cam with 3.73's and 993 heads with 1.84 intake valves, I ran the steel shim head gaskets and I don't ping a bit with 4 VR flat tops. My heads were milled .014" also.
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Old 05-02-2012, 06:47 PM
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Sounds like your pistons are in the hole about the same as the block I am building currently. I found some cheap and good head gaskets that are .026" compressed that I plan to use. They are graphite, which is a great material for head gaskets according to my research. They do tend to leave a lot of hard to remove residue on the block and heads, which is of concern on your next tear down/rebuild. Here they are.
http://www.summitracing.com/parts/CLE-5746/

These gaskets will give you a good quench in the mid .040" range and bump your compression to right about 9.3:1. I think that compression is low for that cam. Check this out, you need to be at 9.5 at a min.
http://www.crankshaftcoalition.com/w..._relationships

Another option would be to send your heads off to get them milled down to take a few CC's out of the chambers. I would bet if you actually measure them you will find they are probably closer to 78+cc's. Yes this would add cost to the project, but cheaper than new heads!

I read an article that said for every .010" of tighter quench you gain 7HP. Yes this is a gross generalization, but still food for thought. Also the pistons run cooler since when they are at TDC heat will transfer to the cooler heads via radiation.

Ultimately those old smogger heads you have are not very good according to today's standards. The biggest problem is those "bath tub" chambers do not promote a thorough mixing of the charge or complete burning of the charge. So by keeping a nice tight quench on those heads, you are helping the mixture/combustion/emissions/power/MPG/detonation in YOUR favor. That is a lot of benefits to leave on the table.

In the end I don't think .058" is really all that bad if you decide to roll with it. I think right now your biggest issue is low compression.

BTW a .015" shim gasket will get to around 9.5:1. But that is going to require a flat deck and flat heads (no warpage).
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Old 05-02-2012, 06:48 PM
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Quote:
Originally Posted by 6426yy
You could run the GMMP .028" gasket and give you .046 quench. I'd stay on the tight side if it were me. My truck is similar, 355 268 cam with 3.73's and 993 heads with 1.84 intake valves, I ran the steel shim head gaskets and I don't ping a bit with 4 VR flat tops. My heads were milled .014" also.
Do you have a part number for this? I didn't think GMPP made gaskets for +.060 overbore?
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Old 05-02-2012, 06:53 PM
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I was looking at the 268 spec on the cam. My thoughts are that your dynamic will be at or around 7.4 to one ( maybe a little less). As long as your cooling system is good and you keep it at or below 180 you should be able to run 89 octane, no problem, if you have decent quench height and have a sizable quench pad and flat top pistons, 87 should be no problem.
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Old 05-02-2012, 08:48 PM
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Thanks, I will definately be looking into those gaskets in the .026-.028 range to help out with my CR. I guess the old copper .040 gaskets will have to wait for another project. I appreciate yall's help greatly.
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Old 05-02-2012, 09:05 PM
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Quote:
Originally Posted by Silver Surfer
BTW a .015" shim gasket will get to around 9.5:1. But that is going to require a flat deck and flat heads (no warpage).
There's something he's not telling here, and I suspect it's that the rotating assembly is 3.75". An Eagle assembly doesn't automatically make it 3.75, I assumed it was stock stroke...Oh well.
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Old 05-02-2012, 10:25 PM
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Many 350 SBC head gaskets are going to have at least a 4.090" gasket bore diameter, usable on a 0.060" over 4" block in other words.

The following is from Old Bogie:
Quote:
FelPro's FEL 1094 a steel shim with a 4.1 bore and .015 thick, if you've got super flat surfaces on the deck and head, this is a great gasket. It does not tolerate the engine being overheated.

Next would be: GM 3830711 also a steel shim with a 4.1 bore it is .026 thick. Good flat surfaces are required, same rules apply as the Fel Pro above. This is the GM production gasket for non 400 bore SBCs. Simple and low cost.

GM 10105117, this baby is a multi-layered stainless steel gasket with a 4.1 bore, it's .028 thick, works with iron or aluminum heads, good for holding back high compression and tolerates some surface irregularities in the deck and head surfaces. (Editor's note: Supposed to be the “revised” gasket, better seal- Post #23 . $21/ea. @ Summit)

GM 14096405, stainless faces over a graphite core, 4.1 bore and .028 thick. This thing hangs tough on uneven surfaces and puts up with high compression ratios. Good for iron or aluminum, this makes a good race engine gasket as it's very tolerant of engines running very hot. It lets the block and head move around to adjust for their temperature differences without breaking its seal.
Other possibilities (nowhere near a complete list):

COMPOSITE TYPE
Victor Reinz Nitroseal p/n 5746- Compressed thickness is 0.025", 4.1” bore. NAPA carries Victor.

SHIM TYPE
Jegs p/n 210044- Embossed Shim w/ Rubber Coating. Bore 4.150", thickness 0.024".

Mr. Gasket p/n 1130 0.018”- 0.020” steel embossed w/coating.

There are several thinner coated shim type gaskets like Fel-Pro Q1094- Fel Pro race head gasket Chevy 307 327 350 283 #1094. Use in some Sportsman drag race and flat top Oval Track categories. Rubber coated steel shim, 4.100 in. bore, 0.015 in. compressed thickness, ~$66/set.

More here.

Last edited by cobalt327; 05-02-2012 at 10:48 PM.
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Old 05-03-2012, 04:52 PM
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http://www.google.com/url?sa=t&rct=j...f2H94AoFZBD9rA

A lot of sites say 4.00" bore but there 4.1 I used them on a 355 with no problems.
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Old 05-03-2012, 08:33 PM
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Quote:
Originally Posted by cobalt327
Many 350 SBC head gaskets are going to have at least a 4.090" gasket bore diameter, usable on a 0.060" over 4" block in other words.

The following is from Old Bogie:


Other possibilities (nowhere near a complete list):

COMPOSITE TYPE
Victor Reinz Nitroseal p/n 5746- Compressed thickness is 0.025", 4.1” bore. NAPA carries Victor.

SHIM TYPE
Jegs p/n 210044- Embossed Shim w/ Rubber Coating. Bore 4.150", thickness 0.024".

Mr. Gasket p/n 1130 0.018”- 0.020” steel embossed w/coating.

There are several thinner coated shim type gaskets like Fel-Pro Q1094- Fel Pro race head gasket Chevy 307 327 350 283 #1094. Use in some Sportsman drag race and flat top Oval Track categories. Rubber coated steel shim, 4.100 in. bore, 0.015 in. compressed thickness, ~$66/set.

More here.
I looked into the Victor Reinz gasket part #5746 and they are listed as race only, not sure what would make a head gasket race only but you think they are ok for a daily driver? Thanks.
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Old 05-04-2012, 01:51 AM
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I don't recall there being any such 'warning' on the gasket packages (came in singles, shrink wrapped), but I used them just once on a 355 SBC w/Trick Flow Twisted Wedge heads when the heads first came out ($720/pair)- so that'll tell you how long ago it was.

You can call the Dana/Victor tech line and see what they have to say.
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Old 05-04-2012, 06:34 PM
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Quote:
Originally Posted by cobalt327
I don't recall there being any such 'warning' on the gasket packages (came in singles, shrink wrapped), but I used them just once on a 355 SBC w/Trick Flow Twisted Wedge heads when the heads first came out ($720/pair)- so that'll tell you how long ago it was.

You can call the Dana/Victor tech line and see what they have to say.
Thanks Cobalt, it is actually on Competition Products website where they are said to be "race only". I will call them early next week to find out and will post their reply. Was that a daily driver you installed them on and if so did you have any probs? Can't imagine what would classify a head gasket race only. Thanks again.
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Old 05-04-2012, 07:00 PM
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Quote:
Originally Posted by GMCBEAST
Thanks Cobalt, it is actually on Competition Products website where they are said to be "race only". I will call them early next week to find out and will post their reply. Was that a daily driver you installed them on and if so did you have any probs? Can't imagine what would classify a head gasket race only. Thanks again.
It was a '72 Camaro 355, TF heads, RMP intake 750 Holley 3310, TH350/3.73 rear gears, driven often but not daily. Never a hint of any problem from the gaskets.

IIRC they are graphite on one side and stainless on the other so need a good finish on the side getting the steel backing because it won't conform readily to irregularities like a full composite gasket. On the engine I used them on, I put the graphite side to the aluminum head and the steel side to the block- which had been milled ~0.010". When the block was milled (done by the owner of the engine), no special instructions were given by him to his machinist for the finish- it came to me that way and that's how I put it together- per his instructions.

The graphite might be the reason for the "race only" warning. A search will get you more I'm sure.
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