PTV issue (yes i searched)
PTV issue (yes i searched) Hi all,
I have been searching since last night and have not found any information. Im wondering if anyone here has run into this
I have an LFA block (aluminum 6.0)
They ahve the LS2/LQ9 pistons and rest of a 6.0 rotating assembly.
I ordered a BTR Stage 4 NA cam for it and i have a set of 243 heads that have been miled .025
Last night i got around to stabbing the cam and checking the pushrod length and the PTV clearance. (no i do not have a degree wheel)
Using the clay method i found out quickly that the exhaust valve hits. and hits early about 3/4 the way up the exhaust lobe. This is with a stock compressed gasket installed.
Now i dont mind having to flycut but i wanted to make sure this is right first. Has anyone ran into this issue? Just for kicks, i removed the exhaust pushrod and rolled the motor over with only the intake side. It cleared fine (which is the bigger lift side as well).
Note, i did call BTR and they recommended using the valve springs to check the PTV not a check spring or the inner dual spring (i tried both but not the actual spring setup)
They said that using the inner spring or a check spring, the preload can cause the valve to drop in about .100-.150. So this might be my problem.
Again, just running it by you all for more ideas, or if anyone has had this happen. I cant check anything until i get home stuck at work all day
I have been searching since last night and have not found any information. Im wondering if anyone here has run into this
I have an LFA block (aluminum 6.0)
They ahve the LS2/LQ9 pistons and rest of a 6.0 rotating assembly.
I ordered a BTR Stage 4 NA cam for it and i have a set of 243 heads that have been miled .025
Last night i got around to stabbing the cam and checking the pushrod length and the PTV clearance. (no i do not have a degree wheel)
Using the clay method i found out quickly that the exhaust valve hits. and hits early about 3/4 the way up the exhaust lobe. This is with a stock compressed gasket installed.
Now i dont mind having to flycut but i wanted to make sure this is right first. Has anyone ran into this issue? Just for kicks, i removed the exhaust pushrod and rolled the motor over with only the intake side. It cleared fine (which is the bigger lift side as well).
Note, i did call BTR and they recommended using the valve springs to check the PTV not a check spring or the inner dual spring (i tried both but not the actual spring setup)
They said that using the inner spring or a check spring, the preload can cause the valve to drop in about .100-.150. So this might be my problem.
Again, just running it by you all for more ideas, or if anyone has had this happen. I cant check anything until i get home stuck at work all day
Your piston to valve minimum is going to be 8-12 degrees before tdc and after tdc, not at max lift. So basically as soon as the intake valve starts opening, it's getting close to the piston, and just as the exhaust valve is almost closed, the pistons runs up and gets close. You can check with checker springs, but there won't be a .100-.150" difference. I would say .020-.030" at the most. I would also recommend using solid lifters when checking. You can take a couple of old lifters and make them solid pretty easy. Basically your only two options is to either fly cut the pistons, or advance the cam. Advancing the cam will lessen the intake p2v clearance, so it's going to be a juggling act, and even then if you get enough on the exhaust, you may not have enough on the intake.
so i have continued to research. And it appears that we checked PTV incorrectly.
What i did not do was rotate cam to the base circle then tighten down the rockers to 0 lash. Instead i just threw the rockers on wherever the cam was and tightened them down
One other question. I have the BTR trunion kit. Do i need to run the stock rocker pedestals?
What i did not do was rotate cam to the base circle then tighten down the rockers to 0 lash. Instead i just threw the rockers on wherever the cam was and tightened them down
One other question. I have the BTR trunion kit. Do i need to run the stock rocker pedestals?
Last edited by steves86ta; Feb 4, 2015 at 04:40 PM.
But ill mess with it tonight and see what happens. Im really thinking that not tightening the rockers while the lifters were on the base circle could have caused my issue.
Atleast i hope
It's not a bad idea. I do it on max effort engines where everything little thing means something. You will gain a little when switching from a checker spring to a real spring. But you can't use a hyd lifter when using that method.
sounds good to me, im going to shim a lifter so it is solid.
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Verdad Gallardo Okay, an update.
Yes checking the PTV clearance the correct way helped me find the issue.
The problem is the damn pushrods are to long. threw my pushrod checker in and was able to come up with a needed length and will be ordering a set
thanks
Yes checking the PTV clearance the correct way helped me find the issue.
The problem is the damn pushrods are to long. threw my pushrod checker in and was able to come up with a needed length and will be ordering a set
thanks