How To Check PTV???????
11-06-2007, 01:05 PM
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How To Check PTV??????? So what is a preferred method of measuring Piston to Vavle clearence? I have heard of using clay? Also i have heard a way of being able to leave the heads on and testing how far the valve drops before it hits the piston.
11-06-2007, 01:25 PM
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Yes you can do clay or the spring method.
Clay method:
1.Pull head
2. Put 1/4 inch of clay on the piston top.
3. Reinstall head and valvetrain.
4. Hand turn motor over a few times.
5. Pull head and remove clay from piston carefully.
6. measure thickness of clay in the valve pocket with a caliper. Standard acceptable thickness is generally .080 intake/.100 exhaust.
Spring Method:
1. Replace one cylinders intake and exhaust valves with a lightweight checker spring.
2. Obtain zero lash with lifters on lobe base.
3. Crank motor to TDC on the exhaust stroke, you will notice both valves will be open at TDC.
4. At TDC you can push down on the valves by hand it will hit the piston top, it is here with you holing the valve down where you use a feeler gauge to measure the distance between the valve stem top and the rocker arm. This is your PTVC.
Clay method:
1.Pull head
2. Put 1/4 inch of clay on the piston top.
3. Reinstall head and valvetrain.
4. Hand turn motor over a few times.
5. Pull head and remove clay from piston carefully.
6. measure thickness of clay in the valve pocket with a caliper. Standard acceptable thickness is generally .080 intake/.100 exhaust.
Spring Method:
1. Replace one cylinders intake and exhaust valves with a lightweight checker spring.
2. Obtain zero lash with lifters on lobe base.
3. Crank motor to TDC on the exhaust stroke, you will notice both valves will be open at TDC.
4. At TDC you can push down on the valves by hand it will hit the piston top, it is here with you holing the valve down where you use a feeler gauge to measure the distance between the valve stem top and the rocker arm. This is your PTVC.
11-06-2007, 01:33 PM
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wait you need 80 thousanths clearance on the intake? and 100 on the exaust?.... is tat because when the motor gets hot the metal expands?
And... will every cylendar be the same?.....or do you have to check them all?
And... will every cylendar be the same?.....or do you have to check them all?
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11-06-2007, 04:23 PM
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when you cut clay with a razor, you get a slight lift from the blade moving the material up and out of the way...
11-06-2007, 04:32 PM
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If the piston has a petroleum film on it (oil, greasy fingerprints, assy lube ect), it will lift right off. Other than that, cut the playdoh into a strip Before you lay it on the piston.
It works out better than it sounds like it would
It works out better than it sounds like it would
11-06-2007, 07:37 PM
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If you are careful the clay will stay the same, you dont use play doh or any crap like that, you use modeling clay since it doesnt expand as easy. It pretty much will keep its shape even if you cut it. I used it to clay my engine and it worked fine for me.
11-06-2007, 08:43 PM
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Rig the valves with light checking springs, and then installing the head and valvetrain with a dial indicator reading off the retainer. Start at 20 degrees BTDC, set the indicator to zero, and then work the exhaust rocker by hand until the valve hits the piston, and read the indicator travel. Repeatedly adjust the crank position 2 degrees forward, re-zero the indicator, and check again. The reading will diminish to the minimum V-to-P value, and then open up again. Next, perform the same procedure on the intake valve, moving from TDC to about 20 degrees after.
This is the most precise way and you need a degree wheel and dial indicator.
This is the most precise way and you need a degree wheel and dial indicator.
11-06-2007, 08:46 PM
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Make sure you use the old GM head bolts if you don't have ARP bolts when torquing the heads down to check PTV clearance, that way you wont waste your new torque to yeild GM head bolts.
11-07-2007, 04:58 AM
#18
Rig the valves with light checking springs, and then installing the head and valvetrain with a dial indicator reading off the retainer. Start at 20 degrees BTDC, set the indicator to zero, and then work the exhaust rocker by hand until the valve hits the piston, and read the indicator travel. Repeatedly adjust the crank position 2 degrees forward, re-zero the indicator, and check again. The reading will diminish to the minimum V-to-P value, and then open up again. Next, perform the same procedure on the intake valve, moving from TDC to about 20 degrees after.
This is the most precise way and you need a degree wheel and dial indicator.
This is the most precise way and you need a degree wheel and dial indicator.
