PTV clay method help
Thread Starter
On The Tree
Joined: Dec 2005
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PTV clay method help Hey Guys,
This weekend I will be checking my PTV using the modeling clay and just had a couple of questions.
1. The reason I am checking this is that I am putting 59cc stage 1 ls6 heads on the car which will require me to change my pushrods. I assume I need the correct pushrod in there while checking the clearance, can I use one of those pushrods you use to measure the right one?
2. How do I make sure that the lifter is pumped up all the way, should I take one of the old ones and weld it up? Anyone have a link to a how to on this?
3. I also need to make sure i have 0 lash between the rocker and valve, is this all the time or at a certain degree?
thanks,
pete
This weekend I will be checking my PTV using the modeling clay and just had a couple of questions.
1. The reason I am checking this is that I am putting 59cc stage 1 ls6 heads on the car which will require me to change my pushrods. I assume I need the correct pushrod in there while checking the clearance, can I use one of those pushrods you use to measure the right one?
2. How do I make sure that the lifter is pumped up all the way, should I take one of the old ones and weld it up? Anyone have a link to a how to on this?
3. I also need to make sure i have 0 lash between the rocker and valve, is this all the time or at a certain degree?
thanks,
pete
Make sure you switch out the valve springs on the cylinder you are checking with some lightweight springs.
Ideally you'll have an adjustable length pushrod, bolt down your rocker arm, and expand the pushrod until it bottoms out on the lifter. Then add the lifter preload amount you want to the length of the expanded pushrod and there's your length.
You can use the adjustable pushrod to check PTV with as well.
Ideally you'll have an adjustable length pushrod, bolt down your rocker arm, and expand the pushrod until it bottoms out on the lifter. Then add the lifter preload amount you want to the length of the expanded pushrod and there's your length.
You can use the adjustable pushrod to check PTV with as well.
I opened an old lifter and removed the spring and added washers so it just fit under the clip. Use the adjustable to check clay, just screw out with the lifter on the cam base circle until zero lash. Don't lube the cam lobes of the ones you are checking, the lube will alter the measured values. Make sure your gasket thickness is correct. I was using 0.040" Cometics and found that drilling the rivets and leaving out one thin layer of the stock GM gaskets came out to just about 0.040". Make sure you push down on the rocker/pushrod while turning the motor, the check springs may not be stiff enough for the lifter to follow the cam.
Thread Starter
On The Tree
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If I'm using the clay method, what is the purpose of installing lighter springs? I planned on turning the motor over with the stock springs on there.
Whistler, do you have a suggested lifter preload that I would add to the 0 lash value?
Whistler, do you have a suggested lifter preload that I would add to the 0 lash value?
"suggested lifter preload" depends on the lifter you will be using in the final build. Morel lifters require between .025 and .040 preload. Stock between .080 and .120. Those numbers may require further reading to verify.
The adjustable will compress and is not well suited for opening a stiff valve spring. It may do it, but your numbers may be overly optimisitc as a result. Using the adjustable pushrod and solid lifter, there is no preload just make sure you are at zero lash. More than zero will show as lower PTV, slop will show as larger PTV so zero lash as the starting point is very important.
Have you considered using the dial indicator method?
Have you considered using the dial indicator method?
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Thread Starter
On The Tree
Joined: Dec 2005
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vette,
Yeah I figured it may have to do with the pushrod being a little weak. I have thought about the dial indicator method because I may be able to get my hands on one. With that method do you just check the clearance at certain intervals like 15 BTDC 5BTDC TDC...? Also either way I go about doing this, do I need to install all of the head bolts or just in the vicinity of the hole that I am checking?
Yeah I figured it may have to do with the pushrod being a little weak. I have thought about the dial indicator method because I may be able to get my hands on one. With that method do you just check the clearance at certain intervals like 15 BTDC 5BTDC TDC...? Also either way I go about doing this, do I need to install all of the head bolts or just in the vicinity of the hole that I am checking?
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MLS head gaskets i took a couple old lifters and did the same thing, added washers and made them solid, then the adj p/r and set at .002 (just so they would seat)
were the .040 cometics MLS gaskets?
were the .040 cometics MLS gaskets?
vette,
Yeah I figured it may have to do with the pushrod being a little weak. I have thought about the dial indicator method because I may be able to get my hands on one. With that method do you just check the clearance at certain intervals like 15 BTDC 5BTDC TDC...? Also either way I go about doing this, do I need to install all of the head bolts or just in the vicinity of the hole that I am checking?
Yeah I figured it may have to do with the pushrod being a little weak. I have thought about the dial indicator method because I may be able to get my hands on one. With that method do you just check the clearance at certain intervals like 15 BTDC 5BTDC TDC...? Also either way I go about doing this, do I need to install all of the head bolts or just in the vicinity of the hole that I am checking?
Yes. I didn't want to use my new gaskets for these measurements and I found that using the GM MLS gasket that came off the car came to the same thickness if I removed one of the thin metal layers and cleaned up the gasket a bit with a scotchbrite pad. Came to approximately 0.041" and I didn't need to use my brand new gaskets.
Thread Starter
On The Tree
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I think if I have a solid lifter in there it will be pretty easy to tell when I am at 0 lash. I also think that preload comes out of the equation when you use a solid lifter too. Does anyone remember what size washer they used so I can have them ready? I guess the number of washers doesn't matter to much as long as you can make up the different with the pushrod length right? Thanks for you help so far
I think if I have a solid lifter in there it will be pretty easy to tell when I am at 0 lash. I also think that preload comes out of the equation when you use a solid lifter too. Does anyone remember what size washer they used so I can have them ready? I guess the number of washers doesn't matter to much as long as you can make up the different with the pushrod length right? Thanks for you help so far
DO NOT subtract preload when using the feeler gauges between the valve tip and rocker arm.When the engine is running the lifters fill with oil and act like they are solid.I use a checker spring on two valves and simply place the gauges between the rocker and valve and turn it over until its at its tightest spot and keep adding more feelers until the valve hits the piston.With the checker spring you can push the valve down with your finger to see how close you are getting.Then at the end measure the feeler gauges and thats your PTV clearance.
Thread Starter
On The Tree
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Hey redtail,
not subtracting the preload makes sense to me for the same reason as you explained. The one thing I'm not liking about the feeler gauge method is that it seems there is room to miss the position where you have the absolute minimum ptv clearance. For it to work you would have to start at some position before tdc and as you turn the motor over every once in awhile you gotta check how close the valve is by pressing it down. I don't think you can just push the valve against the piston and let it ride till it comes up the highest because that would just be TDC, you gotta let the cam drive the valve. It probably isn't as bad as I am making it out to be and I could be wrong but I am probably going to just go with the clay method, my new head gaskets are the stock GM MLS so I can use those for the test.
not subtracting the preload makes sense to me for the same reason as you explained. The one thing I'm not liking about the feeler gauge method is that it seems there is room to miss the position where you have the absolute minimum ptv clearance. For it to work you would have to start at some position before tdc and as you turn the motor over every once in awhile you gotta check how close the valve is by pressing it down. I don't think you can just push the valve against the piston and let it ride till it comes up the highest because that would just be TDC, you gotta let the cam drive the valve. It probably isn't as bad as I am making it out to be and I could be wrong but I am probably going to just go with the clay method, my new head gaskets are the stock GM MLS so I can use those for the test.
yeah i know what you are thinking,once you are there doing it its real simple.Its something thats really worth doing if you dont plan on pulling the heads off the car to see if your cam will fit.But if you have the heads off the car already and have modeling clay,then that way is probably your best bet.
