Tighter quench vs Lower static compression
Thread Starter
Burning Brakes
Joined: Nov 2004
Posts: 800
Likes: 3
From: Port Orange FL
Tighter quench vs Lower static compression
I am assembling my LT1 383 right now and have a small dilemma making a decision on the head gaskets.
If I use a .039 head gasket I end up with .054 quench area, 11.9 to 1 Static compression and 9.3 to 1 Dynamic. I understand this is about as high as I want to be with pump gas.
I can use an impala gasket of .026 and this gets my quench down to .041 but bounces my compression to nearly 12.4 to 1.
The question is which is going to be less likely to detonate?
I am also a little concerned with the tight quench because my pistons are forged with .007 recommended clearance and will probably rock in the bores a bit.
Comments or suggestions?
Thanks
Roy
If I use a .039 head gasket I end up with .054 quench area, 11.9 to 1 Static compression and 9.3 to 1 Dynamic. I understand this is about as high as I want to be with pump gas.
I can use an impala gasket of .026 and this gets my quench down to .041 but bounces my compression to nearly 12.4 to 1.
The question is which is going to be less likely to detonate?
I am also a little concerned with the tight quench because my pistons are forged with .007 recommended clearance and will probably rock in the bores a bit.
Comments or suggestions?
Thanks
Roy
Safety Car
Joined: Apr 2005
Posts: 3,624
Likes: 431
From: Dale City VA
Once it's warmed up bore clearance won't matter.
In my experience, once you get under .040 quench on a 4" bore with most 2618 alloy pistons (.005-.007 clearance), you need to be careful to get oil temp and water temp up before you put any RPM on the motor or the pistons can bump.
My personal street car (LTX based) has 11.66SCR and 8.9DCR.... Reverse dome Manley pistons with .034 quench and .005 bore clearance. New AFR eliminators with the double quench/high swirl chamber. I regularly turn it 7200RPM without problem.
I've been doing some data logging on the car and I do get knock counts which pull 2* of retard between 3000-5000RPM on 93 octane. The car makes a ton of HP and is stupid fast for a NA real street car - BUT.... It is also very fuel sensitive and extremely temp sensitive (engine temp and outside air temp).
I think you can make your's run OK either way - but it'll pull alot of timing under load. Not the best way to do things IMO.
You can do a bunch to open the combustion chamber up and gain some CC's.... IF needed you can also back the camshaft intake centerline up to lower the DCR.... Which will allow you to run the .026 head gasket and still have lower compression.
Will
In my experience, once you get under .040 quench on a 4" bore with most 2618 alloy pistons (.005-.007 clearance), you need to be careful to get oil temp and water temp up before you put any RPM on the motor or the pistons can bump.
My personal street car (LTX based) has 11.66SCR and 8.9DCR.... Reverse dome Manley pistons with .034 quench and .005 bore clearance. New AFR eliminators with the double quench/high swirl chamber. I regularly turn it 7200RPM without problem.
I've been doing some data logging on the car and I do get knock counts which pull 2* of retard between 3000-5000RPM on 93 octane. The car makes a ton of HP and is stupid fast for a NA real street car - BUT.... It is also very fuel sensitive and extremely temp sensitive (engine temp and outside air temp).
I think you can make your's run OK either way - but it'll pull alot of timing under load. Not the best way to do things IMO.
You can do a bunch to open the combustion chamber up and gain some CC's.... IF needed you can also back the camshaft intake centerline up to lower the DCR.... Which will allow you to run the .026 head gasket and still have lower compression.
Will
