Heads fitting intake
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Joined: Jan 2009
Posts: 158
From: Inverness, IL
Heads fitting intake
So I found out my heads might be milled .040 which means I don't know what to do with my intake. The intake itself is a ported LE manifold. Does this mean I have the bottom of the intake milled .040 to match so everything lines up? Whats this going to do to my compression and piston to valve clearance as well?
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Joined: Aug 2002
Posts: 1,509
From: Red Oak Texas
no prob with PTV clearance on LT1 unless the cam is a tooth off.
I have a cpl of customers with 247/255 .668/.668 106 LSa cams on stock bottom ends using LE2 heads with .040" millinga nd no PTV problems.
Fix is to take a 1/2" drill bit and run thru the intake bolt holes.
This allows intake to fit and bolts do not dig into manifold effecting the Tq reading.
Lloyd
I have a cpl of customers with 247/255 .668/.668 106 LSa cams on stock bottom ends using LE2 heads with .040" millinga nd no PTV problems.
Fix is to take a 1/2" drill bit and run thru the intake bolt holes.
This allows intake to fit and bolts do not dig into manifold effecting the Tq reading.
Lloyd
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Joined: Feb 2004
Posts: 1,154
From: VA
Thread Starter
Registered User
Joined: Jan 2009
Posts: 158
From: Inverness, IL
So this whole concept is a bit over my head. What is the stock quench? My car will have stock heads flat milled that are .040 thinner. The gaskets I currently have planned are .039. So that puts me at like .053 thinner than stock. I'm worried about messing everything up as this is my DD. I also don't want to run like 11.5:1 compression either.
My planned cam is .605 intake and .598 exhaust with 224/230 duration and 111 lsa. I'm running pro mag 1.6 rockers, PAC 1518s, ls7 lifters and will have hardened pushrods after the geometry is measured.
Will someone explain this to me in simple terms lol.
My planned cam is .605 intake and .598 exhaust with 224/230 duration and 111 lsa. I'm running pro mag 1.6 rockers, PAC 1518s, ls7 lifters and will have hardened pushrods after the geometry is measured.
Will someone explain this to me in simple terms lol.
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Joined: Aug 2002
Posts: 1,509
From: Red Oak Texas
Make sure the springs are set up at 1.740" with that cam. You want all the pressure you can on that intake lobe.
Quench is the measurement from top of piston to deck surface on cylinder head. The factory 350 has the piston .025-.035" down in the hole at TDC. Even with a .026" head gasket, you end up with a .051-.061 quench. This is FAR from the optimum quench of .030" so you just have to accept this unless the have the block decked and/or change pistons.
If it is a built 355 and the piston is .005" in the hole, you end up with a .031" quench and that is great.
The thicker the quench, the less efficient the engine is. You ahev puddles of air and puddles of fuel as well as some mixed together in the cylinder. As the piston reaches TDC, you ahve air/fuel trapped between the piston and deck of head about 3" across the bore from the spark plug.
the tigheter the quench, the more efficient things work since as the piston nears TDC, it forces the air/fuel into the open part of the chamber so it is mixed much better and all real close to spark the plug so it can be burned and force piston down harder.
You have one piston forced down harder and another piston is forcing more exhaust out so it can fill the cylinder with more fresh air, you have another piston sucking harder on intake port, you have another piston compressing the air/fuel harder so it is mixed even better, etc, etc. it just feeds off of itself and a simple change from .045" to .030" quench can get you 8-10 ft lbs of TQ at EVERY RPM across the board.
the engine will sound better, hit harder, have more vacuum, better throttle response and be LESS prone to detonation.
Lloyd
Quench is the measurement from top of piston to deck surface on cylinder head. The factory 350 has the piston .025-.035" down in the hole at TDC. Even with a .026" head gasket, you end up with a .051-.061 quench. This is FAR from the optimum quench of .030" so you just have to accept this unless the have the block decked and/or change pistons.
If it is a built 355 and the piston is .005" in the hole, you end up with a .031" quench and that is great.
The thicker the quench, the less efficient the engine is. You ahev puddles of air and puddles of fuel as well as some mixed together in the cylinder. As the piston reaches TDC, you ahve air/fuel trapped between the piston and deck of head about 3" across the bore from the spark plug.
the tigheter the quench, the more efficient things work since as the piston nears TDC, it forces the air/fuel into the open part of the chamber so it is mixed much better and all real close to spark the plug so it can be burned and force piston down harder.
You have one piston forced down harder and another piston is forcing more exhaust out so it can fill the cylinder with more fresh air, you have another piston sucking harder on intake port, you have another piston compressing the air/fuel harder so it is mixed even better, etc, etc. it just feeds off of itself and a simple change from .045" to .030" quench can get you 8-10 ft lbs of TQ at EVERY RPM across the board.
the engine will sound better, hit harder, have more vacuum, better throttle response and be LESS prone to detonation.
Lloyd
Registered User
Joined: Jun 2006
Posts: 919
From: New Brunswick,Canada
Make sure the springs are set up at 1.740" with that cam. You want all the pressure you can on that intake lobe.
Quench is the measurement from top of piston to deck surface on cylinder head. The factory 350 has the piston .025-.035" down in the hole at TDC. Even with a .026" head gasket, you end up with a .051-.061 quench. This is FAR from the optimum quench of .030" so you just have to accept this unless the have the block decked and/or change pistons.
If it is a built 355 and the piston is .005" in the hole, you end up with a .031" quench and that is great.
The thicker the quench, the less efficient the engine is. You ahev puddles of air and puddles of fuel as well as some mixed together in the cylinder. As the piston reaches TDC, you ahve air/fuel trapped between the piston and deck of head about 3" across the bore from the spark plug.
the tigheter the quench, the more efficient things work since as the piston nears TDC, it forces the air/fuel into the open part of the chamber so it is mixed much better and all real close to spark the plug so it can be burned and force piston down harder.
You have one piston forced down harder and another piston is forcing more exhaust out so it can fill the cylinder with more fresh air, you have another piston sucking harder on intake port, you have another piston compressing the air/fuel harder so it is mixed even better, etc, etc. it just feeds off of itself and a simple change from .045" to .030" quench can get you 8-10 ft lbs of TQ at EVERY RPM across the board.
the engine will sound better, hit harder, have more vacuum, better throttle response and be LESS prone to detonation.
Lloyd
Quench is the measurement from top of piston to deck surface on cylinder head. The factory 350 has the piston .025-.035" down in the hole at TDC. Even with a .026" head gasket, you end up with a .051-.061 quench. This is FAR from the optimum quench of .030" so you just have to accept this unless the have the block decked and/or change pistons.
If it is a built 355 and the piston is .005" in the hole, you end up with a .031" quench and that is great.
The thicker the quench, the less efficient the engine is. You ahev puddles of air and puddles of fuel as well as some mixed together in the cylinder. As the piston reaches TDC, you ahve air/fuel trapped between the piston and deck of head about 3" across the bore from the spark plug.
the tigheter the quench, the more efficient things work since as the piston nears TDC, it forces the air/fuel into the open part of the chamber so it is mixed much better and all real close to spark the plug so it can be burned and force piston down harder.
You have one piston forced down harder and another piston is forcing more exhaust out so it can fill the cylinder with more fresh air, you have another piston sucking harder on intake port, you have another piston compressing the air/fuel harder so it is mixed even better, etc, etc. it just feeds off of itself and a simple change from .045" to .030" quench can get you 8-10 ft lbs of TQ at EVERY RPM across the board.
the engine will sound better, hit harder, have more vacuum, better throttle response and be LESS prone to detonation.
Lloyd
Thanks.
Thread Starter
Registered User
Joined: Jan 2009
Posts: 158
From: Inverness, IL
Thanks Lloyd. That made this very simple to me and now I'm not nearly as worried. Still with a .039" gasket and the heads milled at .040" I'd be at essentially .024" -.034" quench? Or am I still not fully getting this? Does this mean if I ran a stock .053 gasket that I'd have .037"-.047" quench? The mathematics I'm using are
the stock .025"-.035" into the hole (minus) .040 mill (plus) .053 gasket thickness? = .037-.047? Its late, lol
the stock .025"-.035" into the hole (minus) .040 mill (plus) .053 gasket thickness? = .037-.047? Its late, lol
Last edited by Jon_Esslinger; Jul 15, 2010 at 02:09 AM.
Registered User
Joined: Aug 2002
Posts: 1,509
From: Red Oak Texas
basically it will be the measurement of the deck ht (how far down in the hole the piston is at TDC) plus the head gasket thickness.
The stock LT1 has a .025-.035" deck ht.
this puts the quench at .025-.035" if you did not run a gasket at all. that obviously would not work with no gasket but i am using this example to show you how to measure the quench.
Add the head gasket thickness to that and that is your quench.
.025-.035 deck ht PLUS .026" head gasket = .051-.061.
If using the Fel pro 1074 gasket that is .039" thick, it end up being a .064-.074 quench.
If using the stock GM .051" head gasket, it ends up being .076-.086" quench.
All of these are really horrible so you wanna use the thinnest gasket you can to on a stock bottom end to get the quench tighter and boost compression.
On a built 355/383, the deck ht will be different so you have to measure.
Lloyd
The stock LT1 has a .025-.035" deck ht.
this puts the quench at .025-.035" if you did not run a gasket at all. that obviously would not work with no gasket but i am using this example to show you how to measure the quench.
Add the head gasket thickness to that and that is your quench.
.025-.035 deck ht PLUS .026" head gasket = .051-.061.
If using the Fel pro 1074 gasket that is .039" thick, it end up being a .064-.074 quench.
If using the stock GM .051" head gasket, it ends up being .076-.086" quench.
All of these are really horrible so you wanna use the thinnest gasket you can to on a stock bottom end to get the quench tighter and boost compression.
On a built 355/383, the deck ht will be different so you have to measure.
Lloyd
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