Has anyone dyno'd the difference a head gasket change makes?
Thread Starter
Joined: Nov 2001
Posts: 10,813
Likes: 15
From: Doylestown PA
Has anyone dyno'd the difference a head gasket change makes? I searched, but didn't find a clear answer.
I'm wondering what the gains would be from going from a 0.060" head gasket to a 0.040" gasket. Assume no other changes and that PtoV clearance isn't an issue.
Before anyone screams that it isn't worth it, I've got head studs and can do the work myself, so it would cost me just the price of gaskets and my time, which I enjoy wrenching on the car. So if it gains me 15tq/15hp, I think that would be a great mod.
I'm wondering what the gains would be from going from a 0.060" head gasket to a 0.040" gasket. Assume no other changes and that PtoV clearance isn't an issue.
Before anyone screams that it isn't worth it, I've got head studs and can do the work myself, so it would cost me just the price of gaskets and my time, which I enjoy wrenching on the car. So if it gains me 15tq/15hp, I think that would be a great mod.
TECH Senior Member
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Joined: Apr 2006
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From: Western Burbs of Detroit
Good question bro. Seems that the thinner gasket and tighter quench would raise compression. Sounds like a good project for one of our excellent sponsors.
Maybe Lou, Ron, or Tony can chime in.
Maybe Lou, Ron, or Tony can chime in.
Some info:
-Reducing the HG thickness by 0.020" will reduce the combustion chamber by around 3cc on a stock bore LS1. (0.006" per cc)
-According to this calculator, going from 0.060" gasket to 0.040" will increase SCR by 0.50.
http://www.c5frc.com/calculators/Com...Calculator.htm
-According to the calculator linked below, at 425hp and going from 10:1 to 10.5:1 you would gain around 5hp (~1%).
http://www.bgsoflex.com/crchange.html
-Reducing the HG thickness by 0.020" will reduce the combustion chamber by around 3cc on a stock bore LS1. (0.006" per cc)
-According to this calculator, going from 0.060" gasket to 0.040" will increase SCR by 0.50.
http://www.c5frc.com/calculators/Com...Calculator.htm
-According to the calculator linked below, at 425hp and going from 10:1 to 10.5:1 you would gain around 5hp (~1%).
http://www.bgsoflex.com/crchange.html
Thread Starter
Joined: Nov 2001
Posts: 10,813
Likes: 15
From: Doylestown PA
Well thanks for the responses. I guess it was a question that I've had for a while. We know that torque is derived by cylinder pressure, and when you go to a bigger cam, you blead off this pressure because of the extra overlap, especially at lower rpms. Most people combat or correct this by bumping their compression ratio back up by milling their heads to gain low end torque, which is better drivability (is that a real word??).
I've just been going back and forth with swapping to a bigger cam, but my heads have been milled roughly 0.037, which raises some PtoV clearance issues, especially if I were to run a tighter head gasket.
I've just been going back and forth with swapping to a bigger cam, but my heads have been milled roughly 0.037, which raises some PtoV clearance issues, especially if I were to run a tighter head gasket.
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Don have u measured the deck height before checking which gaskets to use...
-.006 to -.007 with a STOCK piston is the norm but a stroker or built motor can be all over the place depending a few things etc..
For instance lets assume u have +.004 deck height on a few 402's...So if I run the .053 gaskets it would be +.057 which IMO BLOWS....
U need to check the deck to find out which gasket u should run in relation to PTV..Brein u are correct on the assumption that the larger cams can bleed down cyl. psi and this is an easy way to push it back up and keep from loosing power..The DRC/SCR calcutaltor is a viable way of doing this along with some common engine tools...
The engine were doing for Tony as a matter of fact is running a .040 Cometic and after calculating the math this is a good balance...Its worth doin Brien but u need to do the math..Its also worth some power and in turn less chance for detonation
But hey all I do is babble about what cam I am putting in my car from day to day
-.006 to -.007 with a STOCK piston is the norm but a stroker or built motor can be all over the place depending a few things etc..
For instance lets assume u have +.004 deck height on a few 402's...So if I run the .053 gaskets it would be +.057 which IMO BLOWS....
U need to check the deck to find out which gasket u should run in relation to PTV..Brein u are correct on the assumption that the larger cams can bleed down cyl. psi and this is an easy way to push it back up and keep from loosing power..The DRC/SCR calcutaltor is a viable way of doing this along with some common engine tools...
The engine were doing for Tony as a matter of fact is running a .040 Cometic and after calculating the math this is a good balance...Its worth doin Brien but u need to do the math..Its also worth some power and in turn less chance for detonation
But hey all I do is babble about what cam I am putting in my car from day to day
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Verdad Gallardo You guy's make good points.I've seen pistons at 0 deck height and .008 out out the hole. I changed gaskets on 2 different motors and it made no noticable difference.I've also falling off the DCR game too since some testing I did went backwards from where it should of been.
Either way,If you go with a bigger Cam with more overlap it is good to raise the static compression.That does help alot.I just don't see spending the extra $$ on .040 gaskets instead of the .052 GM's.I know people would pay the $$ for a few hp but I see it as a dyno variation.
Either way,If you go with a bigger Cam with more overlap it is good to raise the static compression.That does help alot.I just don't see spending the extra $$ on .040 gaskets instead of the .052 GM's.I know people would pay the $$ for a few hp but I see it as a dyno variation.
Thread Starter
Joined: Nov 2001
Posts: 10,813
Likes: 15
From: Doylestown PA
My whole thing is I love part throttle responsiveness from 2500-4000 rpm, which is why I just swapped to a light flywheel. What a huuuuge difference that was. So if I spend $150 for a set of gaskets, and spend a few hours a night out in the garage after the little ones go to sleep, that's fine with me. I'm going to pull the intake to paint it, and then it's just another hour or so to pull the heads. Granted, it might only be 5-10 hp at wot, but I'm wondering how the part throttle would respond.
From what Tommy and Joe Prince said, I'd benefit going to a 228/232 cam, but I would have some concerns about piston to valve clearance, which then leads me to flycutting, which then hurts dynamic compression again.
Once I finish getting my tune squared away, I'm going to toss it on a dyno and see where I'm at. Maybe I'll just leave well enough alone till I decide to go bigger cubes or FI down the road.
From what Tommy and Joe Prince said, I'd benefit going to a 228/232 cam, but I would have some concerns about piston to valve clearance, which then leads me to flycutting, which then hurts dynamic compression again.
Once I finish getting my tune squared away, I'm going to toss it on a dyno and see where I'm at. Maybe I'll just leave well enough alone till I decide to go bigger cubes or FI down the road.
