Piston to valve clearance question
Thread Starter
Instructor
Joined: Dec 2005
Posts: 241
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From: Aubrey TX
Piston to valve clearance question
I'm building a 383 stroker and just finished up installing the pistons and for the next step I want to check my piston to valve clearance. I read the various methods used and want to go with the clay method.
I am using hydraulic retro roller lifters and know that the valve springs will collapse the lifters so I was thinking of using lite test springs on the heads for the test. I will put clay on the piston, oil on the valves so the clay does not stick and install the test gasket, head and all valve train components and adjust the rockers so the push rod just encounters resistance, not to collapse the lifter. Rotate the engine two times past TDC and disassemble and measure.
Does anyone see a problem with this method, especially using the lite springs to avoid lifter collapse?
I am using hydraulic retro roller lifters and know that the valve springs will collapse the lifters so I was thinking of using lite test springs on the heads for the test. I will put clay on the piston, oil on the valves so the clay does not stick and install the test gasket, head and all valve train components and adjust the rockers so the push rod just encounters resistance, not to collapse the lifter. Rotate the engine two times past TDC and disassemble and measure.
Does anyone see a problem with this method, especially using the lite springs to avoid lifter collapse?
Thread Starter
Instructor
Joined: Dec 2005
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From: Aubrey TX
I was going to go to the hardware store and match up a spring the same size but with lighter pressure.
One thing I did forget to mention, the lifters where previously used on this engine and are not new. They have been primed due to previous use.
One thing I did forget to mention, the lifters where previously used on this engine and are not new. They have been primed due to previous use.
Team Owner
Joined: Apr 1999
Posts: 21,953
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
What are your cam specs and what do your piston valve reliefs look like. Modern forgings even JE SRP's have more than enough clearance for up to .700 lift and over 250 Duration.
on H-lifters I just tighten them down to take out the plunger pump up and rotate the motor with a dial indicator on the rocker to ensure that it is getting the advertised lift.
I personally have never used lighter test springs to measure stuff. I have used breakin springs on monster racing roller cams at the shop
on H-lifters I just tighten them down to take out the plunger pump up and rotate the motor with a dial indicator on the rocker to ensure that it is getting the advertised lift.
I personally have never used lighter test springs to measure stuff. I have used breakin springs on monster racing roller cams at the shop
Race Director
Joined: Apr 2000
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
I use light test springs from Comp or Crane, they are 10 bucks. You only need to do one cylinder.
I don't bother with the gasket when I put the head on, just add the compressed thickness to you measurements or don't even bother doing that for more of a safety margin.
You put the test springs on the valves and get a dial indicator and set it on one side of the retainer. You rotate the motor slowly pressing down on the valve with you finger each time you rotate it a bit and looking at the dial indicator as the readings get smaller and smaller.
Don't worry about TDC or specific degree, where the piston is closest to the valve whether intake or exhaust is way off TDC to each side.
Once the dial indicator starts to read higher and higher you know you have passed the PtV clearance. Rotate again and try and make sure you have the correct reading.
Minimum .100" for exhaust and .080" for intake. To be honest I don't think you have anything to worry about but I would do it on any motor I built. My 427ci with .640" lift has more than enough PtV clearance
I don't bother with the gasket when I put the head on, just add the compressed thickness to you measurements or don't even bother doing that for more of a safety margin.
You put the test springs on the valves and get a dial indicator and set it on one side of the retainer. You rotate the motor slowly pressing down on the valve with you finger each time you rotate it a bit and looking at the dial indicator as the readings get smaller and smaller.
Don't worry about TDC or specific degree, where the piston is closest to the valve whether intake or exhaust is way off TDC to each side.
Once the dial indicator starts to read higher and higher you know you have passed the PtV clearance. Rotate again and try and make sure you have the correct reading.
Minimum .100" for exhaust and .080" for intake. To be honest I don't think you have anything to worry about but I would do it on any motor I built. My 427ci with .640" lift has more than enough PtV clearance
Burning Brakes
Joined: Mar 2004
Posts: 816
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From: Finland
What if you then find a bit too tight valve to piston clearance..what are the options? Just remove material from pistons or thicker gasket or change cam base timing or?? And any disadvantakes of the option schosen?
Team Owner
Joined: Apr 1999
Posts: 21,953
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
I off hand think that you might have a compression problem. How many cc's are those Vortec heads?
VESA - the only true option is piston valve relief machining. KB flat tops just have a couple of half *** notches and claying is the correct method to check them
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Race Director
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Last edited by MotorHead; Nov 18, 2009 at 03:12 PM.
Thread Starter
Instructor
Joined: Dec 2005
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From: Aubrey TX
gkull,
The heads are 64cc. I know the compression will be way up there. I calculated about 10:3. As long as I can run on premium pump gas I will be fine.
MotorHead,
Thanks for the info. Looks like a good procedure but I really want to clay them out to be sure.
So, going back to my original question, does anybody see a problem with the procedure and especially using a test spring to avoid llifter compression?
The heads are 64cc. I know the compression will be way up there. I calculated about 10:3. As long as I can run on premium pump gas I will be fine.
MotorHead,
Thanks for the info.
Looks like a good procedure but I really want to clay them out to be sure. So, going back to my original question, does anybody see a problem with the procedure and especially using a test spring to avoid llifter compression?
Drifting
Joined: May 2005
Posts: 1,629
Likes: 4
From: Somers CT
gkull,
The heads are 64cc. I know the compression will be way up there. I calculated about 10:3. As long as I can run on premium pump gas I will be fine.
MotorHead,
Thanks for the info. Looks like a good procedure but I really want to clay them out to be sure.
So, going back to my original question, does anybody see a problem with the procedure and especially using a test spring to avoid llifter compression?
The heads are 64cc. I know the compression will be way up there. I calculated about 10:3. As long as I can run on premium pump gas I will be fine.
MotorHead,
Thanks for the info.
Looks like a good procedure but I really want to clay them out to be sure. So, going back to my original question, does anybody see a problem with the procedure and especially using a test spring to avoid llifter compression?
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
gkull,
The heads are 64cc. I know the compression will be way up there. I calculated about 10:3. As long as I can run on premium pump gas I will be fine.
So, going back to my original question, does anybody see a problem with the procedure and especially using a test spring to avoid llifter compression?
The heads are 64cc. I know the compression will be way up there. I calculated about 10:3. As long as I can run on premium pump gas I will be fine.
So, going back to my original question, does anybody see a problem with the procedure and especially using a test spring to avoid llifter compression?
Thread Starter
Instructor
Joined: Dec 2005
Posts: 241
Likes: 0
From: Aubrey TX
Thanks guys! I guess I will give it a try and see.
I just wanted to see if this procedure would be valid with a test spring. If I get real close piston to valve clearance then I will look into it better.
I just wanted to see if this procedure would be valid with a test spring. If I get real close piston to valve clearance then I will look into it better.
