Improve quench with head gasket?
12-09-2005, 08:45 AM
#42
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Re: Improve quench with head gasket?
Originally Posted by PatriYacht
There's a flat area on the piston that matches a flat area on the head. That's your quench area. You need about .040 between the two so they do not hit at high rpm. You also need to get them as close as possible so that the air fuel mixture is sqeezed out causing turbulence in the rest of the chamber causing less detonation.
In most cases, from the factory, the piston is down in the block .010-.020. A Felpro blue teflon gasket is .042 thick. Added together you are above what most builders consider a good quench. Cometic gaskets are as thin as .020 (I don't have the catalog in front of me) and come in other sizes so you can choose your quench thickness. Or you can have the block zero decked, mill the deck of the block even with the pistons and use the Felpro gasket.
Experienced engine builders say that proper quench makes such a large difference that engines will keep running better right up to the point that pistons hit cylinder heads. Conversly, adding thicker head gaskets to lower compression will usually make detonation worse because you're making the quench distance to large.
In most cases, from the factory, the piston is down in the block .010-.020. A Felpro blue teflon gasket is .042 thick. Added together you are above what most builders consider a good quench. Cometic gaskets are as thin as .020 (I don't have the catalog in front of me) and come in other sizes so you can choose your quench thickness. Or you can have the block zero decked, mill the deck of the block even with the pistons and use the Felpro gasket.
Experienced engine builders say that proper quench makes such a large difference that engines will keep running better right up to the point that pistons hit cylinder heads. Conversly, adding thicker head gaskets to lower compression will usually make detonation worse because you're making the quench distance to large.
Excellent information.
You say that "You need about .040 between the two so they do not hit at high rpm". How does one find/figure out what is the hard number for the maximum quence one can use in gasket thickness sellection for a specific engine with out risk of piston to head contact. Specifically I will be upgrading my stock 496HO (2005) this winter with cam and heads and want to determine the hard number for my maximum quench to target. The stock cast aluminum pistons and steel rods will be retained.
I understand having to determine the current piston to deck distance.
Thanks!
12-09-2005, 09:08 AM
#43
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Re: Improve quench with head gasket?
Rage, the cylinder head is flat. It's the part of the head that gets milled flat when you surface the head so you don't have to measure anything there. All you do is bring a piston to top dead center and measure how far down the piston is. If it's down .010, use a .030 thick head gasket. If it's down .015, use a .025 gasket.
Last edited by PatriYacht; 12-09-2005 at 12:57 PM.
12-09-2005, 10:51 AM
#45
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Re: Improve quench with head gasket?
Originally Posted by PatriYacht
Rage, the cylinder head is flat. It's the part of the head that gets milled flat when you surface the head so you don't have to measure anything there. All you do is bring a piston to top dead center and measure how far down the piston. If it's down .010, use a .030 thick head gasket. If it's down .015, use a .025 gasket.
So 0.040 inch quench minimum clearance IS the hard number to insure nothing hits at high rpm's regardless of the engine?
Thanks!
12-09-2005, 12:33 PM
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Re: Improve quench with head gasket?
Originally Posted by Nordicflame
Your explaination was not forgot!
So far I have heard "about .0.040" or "~0.040" is max quench to use with steel connecting rods to be sure that at high rpm's the piston does not hit the head or valves. What I am looking for is a "hard number" instead of "about" or "~" number. With the hard number I would do as you suggest, measure the deck height of all pistons, take the smallest deck height measurement and subtract that value from the hard number for maximum safe quench and use that remainder as the thickness of head gasket to buy and to install with the knowledge that the cast hypereutectic aluminum pistons in my engine will never hit anything and shatter into a thousand pieces.
Thanks as always for your help and patience!
