Head gasket thickness
Le Mans Master
Joined: Jun 2004
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From: Seattle WA
St. Jude Donor '14
If we're talking about the difference between something approaching .040 quench or something more like .060 quench, it's more about the HP/TQ gains since it also affects the engine's detonation sensitivity.
Burning Brakes
Joined: Mar 2008
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From: Middle Of Kali CA
I have heard this. Is it because more room for carbon to build? Or what?
Race Director
Joined: Oct 2002
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From: Gone
CI 6-7-8-9-10 Veteran
St. Jude Donor '03
You can run quench as little as .030" and likely not have any issues.
And no, peak lift (alone) does not directly affect p/v clearance. You can make a .580" lift cam easily hit the pistons, and you can make an .800" lift lobe never come close.
The reason most people think it does, is because of cam lobe design...Higher lifts are a natural byproduct of longer duration in most every lobe. If you cut off the top of a steep lobe to create less total lift, you did absolutely nothing to gain p/v clearance.
And no, peak lift (alone) does not directly affect p/v clearance. You can make a .580" lift cam easily hit the pistons, and you can make an .800" lift lobe never come close.
The reason most people think it does, is because of cam lobe design...Higher lifts are a natural byproduct of longer duration in most every lobe. If you cut off the top of a steep lobe to create less total lift, you did absolutely nothing to gain p/v clearance.
Team Owner
Joined: Mar 1999
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From: At the beach in little Rhody
No, it has more to do with turbulence and flow characteristics when the fuel is ignited. Good read here 
Le Mans Master
Joined: Jun 2004
Posts: 6,231
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From: Seattle WA
St. Jude Donor '14
I didn't see anyone state that peak lift (alone) affected P/V, but the reverse was stated...
Thread Starter
Instructor
Joined: Jun 2008
Posts: 220
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From: Somers Point New Jersey
What i need is someone to tell me that they milled their head .060" and use a high duration cam with no probs 
I believe our low valve angle is very forgiving when it comes to PTV clearance.
I am going to stay safe and try to keep .040" quench as I have stock rods and will be running high rpm.
I believe our low valve angle is very forgiving when it comes to PTV clearance.
I am going to stay safe and try to keep .040" quench as I have stock rods and will be running high rpm.
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Tech Contributor
Joined: Sep 2005
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From: New Market AL
Originally Posted by Chevy406
Total valve lift doesn't affect piston to valve clearance....
Originally Posted by billa
didn't see anyone state that peak lift (alone) affected P/V, but the reverse was stated...
Le Mans Master
Joined: Jun 2004
Posts: 6,231
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From: Seattle WA
St. Jude Donor '14
Bottom line is that you need to measure it...and check your valvetrain geometry. And, as noted anything over about .020 change in deck height is going to affect the intake.
I have to admit that I still don't completely understand what you're trying to achieve :/
Last edited by billla; Sep 23, 2008 at 08:15 PM.
Le Mans Master
Joined: Jun 2004
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From: Seattle WA
St. Jude Donor '14
Team Owner
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From: At the beach in little Rhody
Thread Starter
Instructor
Joined: Jun 2008
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From: Somers Point New Jersey
He is always on the phone with casey asking for advice or opinions.I talked to him last night and he said he knew someone that milled the head something crazy like .100" and used a 240 cam or something huge and they had no PTV probs.
If no one has done what I am doing, then would anyone like to share PTV problems they have experienced with stock/milled heads?
Race Director
Joined: Oct 2002
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From: Gone
CI 6-7-8-9-10 Veteran
St. Jude Donor '03
really?? he is going to cut the intake surface also that it will bolt up normally, thought that was normal to do. The guy I am using is a close friend and was taught by casey at SAM. He specializes in LS1 and pro stock stuff so if he wants to sink the valve thats what I'm gonna let him do. He is always on the phone with casey asking for advice or opinions.
I talked to him last night and he said he knew someone that milled the head something crazy like .100" and used a 240 cam or something huge and they had no PTV probs.
If no one has done what I am doing, then would anyone like to share PTV problems they have experienced with stock/milled heads?
He is always on the phone with casey asking for advice or opinions.I talked to him last night and he said he knew someone that milled the head something crazy like .100" and used a 240 cam or something huge and they had no PTV probs.
If no one has done what I am doing, then would anyone like to share PTV problems they have experienced with stock/milled heads?
You seem to have a pro race team with immense knowledge and experience doing your work, yet you ask here about quench and gasket thickness details, and inability to measure such details...kind of odd, if not a changing story.
I'm running 59cc big valve 5.3 heads that were milled .025" with a .040" gasket and a 240/244 111 lsa cam. That produced a negative p/v clearance value (also called interference) which flycutting cured. (I didn't sink the valves though).
!0k or so miles on the setup, not had a problem with it yet. Rev limit is set at 7200. YMMV.
Thread Starter
Instructor
Joined: Jun 2008
Posts: 220
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From: Somers Point New Jersey
I'm not saying what you are talking about doing is impossible....I meant good luck finding someone else who's done it and can share experience.
You seem to have a pro race team with immense knowledge and experience doing your work, yet you ask here about quench and gasket thickness details, and inability to measure such details...kind of odd, if not a changing story.
I'm running 59cc big valve 5.3 heads that were milled .025" with a .040" gasket and a 240/244 111 lsa cam. That produced a negative p/v clearance value (also called interference) which flycutting cured. (I didn't sink the valves though).
!0k or so miles on the setup, not had a problem with it yet. Rev limit is set at 7200. YMMV.
You seem to have a pro race team with immense knowledge and experience doing your work, yet you ask here about quench and gasket thickness details, and inability to measure such details...kind of odd, if not a changing story.
I'm running 59cc big valve 5.3 heads that were milled .025" with a .040" gasket and a 240/244 111 lsa cam. That produced a negative p/v clearance value (also called interference) which flycutting cured. (I didn't sink the valves though).
!0k or so miles on the setup, not had a problem with it yet. Rev limit is set at 7200. YMMV.
Race Director
Joined: Oct 2002
Posts: 16,477
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From: Gone
CI 6-7-8-9-10 Veteran
St. Jude Donor '03
I have to ask...what heads are you using that you need to mill that much?
What is your desired compression ratio?
What are your cam specs?
Sinking the valve seats in the heads is an alternative to flycutting, yeah...but to be honest, I do not know how much (depth) you can get away with there. And if not compensating by shortening the valve stems, what does that do to rocker geometry?
There's a number of things you said will be done, that most haven't done, and people certainly can't predict what kind of clearances you'll end up with with those relatively "unknown" modifications.
Not picken on ya...just sayin...
What is your desired compression ratio?
What are your cam specs?
Sinking the valve seats in the heads is an alternative to flycutting, yeah...but to be honest, I do not know how much (depth) you can get away with there. And if not compensating by shortening the valve stems, what does that do to rocker geometry?
There's a number of things you said will be done, that most haven't done, and people certainly can't predict what kind of clearances you'll end up with with those relatively "unknown" modifications.
Not picken on ya...just sayin...
Thread Starter
Instructor
Joined: Jun 2008
Posts: 220
Likes: 0
From: Somers Point New Jersey
I have to ask...what heads are you using that you need to mill that much?
What is your desired compression ratio?
What are your cam specs?
Sinking the valve seats in the heads is an alternative to flycutting, yeah...but to be honest, I do not know how much (depth) you can get away with there. And if not compensating by shortening the valve stems, what does that do to rocker geometry?
There's a number of things you said will be done, that most haven't done, and people certainly can't predict what kind of clearances you'll end up with with those relatively "unknown" modifications.
Not picken on ya...just sayin...
What is your desired compression ratio?
What are your cam specs?
Sinking the valve seats in the heads is an alternative to flycutting, yeah...but to be honest, I do not know how much (depth) you can get away with there. And if not compensating by shortening the valve stems, what does that do to rocker geometry?
There's a number of things you said will be done, that most haven't done, and people certainly can't predict what kind of clearances you'll end up with with those relatively "unknown" modifications.
Not picken on ya...just sayin...
Well, he just bought me a set of 5.3 heads to be delivered on monday. He will be selling my heads on ebay. They are done up very nicely and if anyone wants them I can get flow numbers, pictures, whatever. I imagine they flow around 300cfm at .600. But anyway, to answer your questions:
They are stock LS1 heads
Trying to get 11-11.5:1 compression ratio. Preferably the highest.
We were going to take care of that by shimming the rockers .030" because that's how much he sank the valves, then measure for pushrod length. I was on his *** about making sure I could keep my correct geometry.
As you can see, this was kind of doing it "the hard way".
So since the 5.3 heads have the same ports but shallower chambers, we have decided that the same results can be accomplished without milling with 5.3 heads with my 2.000" valves.
After all that....
I want my car back dammit
