Quench with a Supercharger
Quench with a Supercharger Trying to determine gasket size and keep a good quench # with a supercharger.
4.127" Bore
4.0" Stroke
6.125"Rod Length
68CC Combustion chamber
.030" Piston to Deck (in hole)
-25CC dished pistons
44 ADV intake close angle
228 ADV intake duration
240 ADV exhaust duration
114 lobe separation
110 intake lobe centerline
Also, would like to keep compression around 9.5:1
4.127" Bore
4.0" Stroke
6.125"Rod Length
68CC Combustion chamber
.030" Piston to Deck (in hole)
-25CC dished pistons
44 ADV intake close angle
228 ADV intake duration
240 ADV exhaust duration
114 lobe separation
110 intake lobe centerline
Also, would like to keep compression around 9.5:1
Doesn't matter if you have forced induction or not, having good piston quench is never a bad thing.
First of all we need to find out if quench is even a concern for you.
What kind of pistons do you have? If the dish in your pistons looks like factory dish pistons (like a round bowl) forget worrying about quench because the pistons don't have a quench area to worry about. Good aftermarket dished pistons are made that only the valve relief area has the dish, then a flat area for the quench. Usually they have a bathtub shaped dish.
So if you have decent pistons like I described, usually 0.040" (including head gasket) is optimum. I've build motors with quench as tight as 0.030" (including head gasket), but that's getting risky. Anything above 0.050" quench and you've lost all benefit of having good quench.
So if you can get a 0.020" or less gasket or 0.00 deck the block you could run a 0.040" head gasket, either way you'd be in good shape.
First of all we need to find out if quench is even a concern for you.
What kind of pistons do you have? If the dish in your pistons looks like factory dish pistons (like a round bowl) forget worrying about quench because the pistons don't have a quench area to worry about. Good aftermarket dished pistons are made that only the valve relief area has the dish, then a flat area for the quench. Usually they have a bathtub shaped dish.
So if you have decent pistons like I described, usually 0.040" (including head gasket) is optimum. I've build motors with quench as tight as 0.030" (including head gasket), but that's getting risky. Anything above 0.050" quench and you've lost all benefit of having good quench.
So if you can get a 0.020" or less gasket or 0.00 deck the block you could run a 0.040" head gasket, either way you'd be in good shape.
Last edited by Ford_Assassin; Nov 17, 2008 at 11:23 PM.
Also a good way to tighten up your quench area is to not only make sure that the gasket is as close to the bore as possible but, you can also lower your deck height to actually bring the piston a little farther out of the block, this will use the top of the piston to tighten up the quench area.
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That deck height with the piston .030" in the hole is going to mess you up - not many gaskets to choose from to get the quench you want. You would be way better off decking the block to 0", then you have a wide range of excellent gaskets to choose from.
It will also help get your CR closer to the 9.5:1 range. As it is, your numbers yield a 9.08:1 CR with a .040" gasket.
You could get closer to the range with a thin copper gasket, but they have some sealing issues and you might need to o-ring.
Jim
It will also help get your CR closer to the 9.5:1 range. As it is, your numbers yield a 9.08:1 CR with a .040" gasket.
You could get closer to the range with a thin copper gasket, but they have some sealing issues and you might need to o-ring.
Jim
thanks guys, after all these different suggestion I've decided to deck the block to .005" and go with a .040" Cometic MLS gasket. I'll let you know how it turns out.
