Checking P/V clearance discussion
Checking P/V clearance discussion A coworker and I were discussing methods of checking p/v clearance. He said he used the clay method. I told him I didn't like the idea of clay so much as the results can easily be skewed if you aren't very good. He knew what I meant. He said he didn't like the light valvesprings and dial indicator method as much. As the valves come down at an angle (23 degrees, 15 degrees or whatever you have), and you push down the valve, you are actually measuring the hypotenuse of the triangle instead of the leg which is what the clay is measuring. I can definitely see his point. Does anybody ever figure in the angle of the valve coming down using the Pythagorean Theorem?
Really??
This is exaggerated to show what I'm talking about. X is what the clay is measuring. Y is what the light valvesprings are measuring. There is a difference.
This is exaggerated to show what I'm talking about. X is what the clay is measuring. Y is what the light valvesprings are measuring. There is a difference.
LOL, X and Y are the same distance. The bottom edge of the valve is what hits the piston top when you check with the spring method which is the same edge of the valve that digs into and will go the deepest into the clay.
OK lol. Forget about the arrow for a second (only representing valve movement which is obvious). You are trying to blow me off too quick instead of thinking about it. The X and Y are representing legs on the triangle.
Im not blowing you off, you are just wrong and now that i look again and read what you said X is not even what is measured with the clay. The clay indents at the angle of the valve which is Y on the bottom edge of the valve.
X can not be the clay because that line goes striaght down and the valve does not. X would be dead air space.
Y is what is measured with the spring and the clay.
Now enough with theory, lets talk real life. Ive done it both ways and the measurements are the same.
X can not be the clay because that line goes striaght down and the valve does not. X would be dead air space.
Y is what is measured with the spring and the clay.
Now enough with theory, lets talk real life. Ive done it both ways and the measurements are the same.
OK someone will get it. You and I are not on the same page.
The clay most definitely measures X when the piston and valve are at their closest clearance. I don't care what angle the valve goes to get there. You are, no doubt, measuring X after the piston and valve quit coming towards each other with claying.
With the dial indicator, you stop the piston at TDC (and points near that) and push the valve down at the angle and get Y measurement. No doubt about that one either.
Think of it like this Brad, after you cut away the clay so you can take your calipers to it, you are measuring up and down (perpendicular in respect to the piston) or the thickness of the clay. Again X on the triangle. With the dial indicator, think of the angle it is on in respect to the piston which is the angle of the valve. That angle is representing Y on the triangle. That should paint a picture. I was just curious if people are figuring this difference in.
Not trying to argumentative, but rather have a decent conversation about it. I kinda figured this sort of thing has been discussed before but there would be many p;v clearance threads to go through to find it.
The clay most definitely measures X when the piston and valve are at their closest clearance. I don't care what angle the valve goes to get there. You are, no doubt, measuring X after the piston and valve quit coming towards each other with claying.
With the dial indicator, you stop the piston at TDC (and points near that) and push the valve down at the angle and get Y measurement. No doubt about that one either.
Think of it like this Brad, after you cut away the clay so you can take your calipers to it, you are measuring up and down (perpendicular in respect to the piston) or the thickness of the clay. Again X on the triangle. With the dial indicator, think of the angle it is on in respect to the piston which is the angle of the valve. That angle is representing Y on the triangle. That should paint a picture. I was just curious if people are figuring this difference in.
Not trying to argumentative, but rather have a decent conversation about it. I kinda figured this sort of thing has been discussed before but there would be many p;v clearance threads to go through to find it.
Last edited by frito1; Jul 22, 2008 at 12:42 AM. Reason: More clarification
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Youre right, Ive done it both ways myself on the same motor and got the same distances so you can throw your theory out the window because the back to back tests are all the proof you need.
Have you ever actually ever done this before? And yes there are lots of PTVC threads around here. Both methods have been used by racers for years.
Have you ever actually ever done this before? And yes there are lots of PTVC threads around here. Both methods have been used by racers for years.
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I like dial indicators precision!!
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Joined: Mar 2004
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From: BFE
geometry is not wrong, claying is for flat tappet motors.
With the hydraulic, there is only one way that is accurate, the dial indicator method. That requires both modified lifter and lighht spring.
Also organic clay needs to be used. It works but we have to get on with advanced tech.
With the hydraulic, there is only one way that is accurate, the dial indicator method. That requires both modified lifter and lighht spring.
Also organic clay needs to be used. It works but we have to get on with advanced tech.
Is X axis at 90 degrees to the piston and Y axis is the same angle as the valve? If so, and you are measuring an aftermarket piston, with a precut valve notch, then you would have to measure Y to get a true clearance mearurement.
I think you'd both (OP and co worker) would have a better understanding after CUTTING for PTVC.
Take a fly cutter, cut straight down, piston at TDC. Look at the cut, it's easier if it's a deep one, it's rough.
Mock it all back up and rotate it over, if the other angle is a problem you'll see the rub marks in the rough cut.
In this case you need to put your cutter down on the stop and rotate the engine, this way you don't need to get into the Pythagorean Theorem, you get into engine operating dynamics and real angles not theories.
In other words X is your base cut and Y is removed during engine rotation.
Then you can get working on other areas of this LSX powered space shuttle.
Take a fly cutter, cut straight down, piston at TDC. Look at the cut, it's easier if it's a deep one, it's rough.
Mock it all back up and rotate it over, if the other angle is a problem you'll see the rub marks in the rough cut.
In this case you need to put your cutter down on the stop and rotate the engine, this way you don't need to get into the Pythagorean Theorem, you get into engine operating dynamics and real angles not theories.
In other words X is your base cut and Y is removed during engine rotation.
Then you can get working on other areas of this LSX powered space shuttle.