Finding zero lash for PTV check
Thread Starter
Drifting
Joined: Apr 2009
Posts: 1,898
Likes: 9
From: Morrisville PA
Finding zero lash for PTV check
I am using the feeler gauge method to check my ptv with a solid lifter and a checking spring. I am having odd zero lash findings. I am measuring at TDC with both cyl #1 valves closed. I came up with only 7.2 on my adjustable comp PR checker. This seems way off to me. I even tried 7.225, but as soon as the rocker gets snug, I can clearly see the checking spring compressing slightly, so it is not zero lash.
Do you need to use the EO/IC method to find zero lash instead of at TDC?
Car has 799 heads milled .030 and the cam I am installing is a 227/235 on a 114. It could be close without flycutting so I want to make sure I do this right. With the PR at 7.2, I got .120 exhaust clearance, but I don't trust the measurement. There is no way this car will only need 7.250 pushrods. I was running 7.325 pushrods with the 226/230 cam.
The lifters are LS7 lifters.
Do you need to use the EO/IC method to find zero lash instead of at TDC?
Car has 799 heads milled .030 and the cam I am installing is a 227/235 on a 114. It could be close without flycutting so I want to make sure I do this right. With the PR at 7.2, I got .120 exhaust clearance, but I don't trust the measurement. There is no way this car will only need 7.250 pushrods. I was running 7.325 pushrods with the 226/230 cam.
The lifters are LS7 lifters.
Last edited by mchicia1; Apr 30, 2012 at 11:32 PM.
Thread Starter
Drifting
Joined: Apr 2009
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From: Morrisville PA
I built it out of an ls7 lifter. I don't know if it is exactly the same height as the others but it is damn close by eyeballing it. But even with a regular lifter, I had the same results...7.2 pushrod. Makes no sense, I must not be all the way on the base circle or something.
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From: Jackson Tn
St. Jude Donor '06-'07-'08-'09
I built it out of an ls7 lifter. I don't know if it is exactly the same height as the others but it is damn close by eyeballing it. But even with a regular lifter, I had the same results...7.2 pushrod. Makes no sense, I must not be all the way on the base circle or something.
Thread Starter
Drifting
Joined: Apr 2009
Posts: 1,898
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From: Morrisville PA
But like I said, I was still getting 7.2 with a regular LS7 lifter. I am going to double check today if it doesnt rain. Will update thread.
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From: Portland OR
What rockers?
With the stockers, I remember one fellow forgetting to put the rocker stand on first.
The cam should be on the base circle at TDC. Certainly not as far off as your numbers are indicating.
With the stockers, I remember one fellow forgetting to put the rocker stand on first.
The cam should be on the base circle at TDC. Certainly not as far off as your numbers are indicating.
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Safety Car
Joined: Aug 2011
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From: Portland OR
Do you have the lifter trays in? I found that I had to remove them for the measurements, they hold the lifter up when you don't have any spring pressure.
Push the pushrod down with your finger to make sure it is on the cam.
Probably obvious, but might as well ask.
Cam degreed?
Push the pushrod down with your finger to make sure it is on the cam.
Probably obvious, but might as well ask.
Cam degreed?
Thread Starter
Drifting
Joined: Apr 2009
Posts: 1,898
Likes: 9
From: Morrisville PA
**Update**
Ok so my zero lash was off by .050
. The lifter trays were holding the lifters up because I didn't push down the lifter before I took my measurement. Whoops.
So I remeasured and got a hair below 7.250, which makes a lot more sense. I remeasured PTV and came up with .105 for the exhaust and .067 for the intake. The intake was tightest right after tdc...maybe 1 or 2 degrees and kept getting more and more room from there. Right after TDC is where I got my .067 measurement.
All I did this time was find where the tightest area was by looking at how much the spring compressed....I just eyeballed it. Then I took off the checking spring to let the valve drop all the way down, then I stuck my feeler gauges in as I slowly turned the motor over in that area between about 1 and 6 degrees atdc for intake and btdc for exhaust.
I am confident in my #'s now!
Thanks everyone, now the hard part is over and I can just bolt the car back together.
Ok so my zero lash was off by .050
. The lifter trays were holding the lifters up because I didn't push down the lifter before I took my measurement. Whoops.So I remeasured and got a hair below 7.250, which makes a lot more sense. I remeasured PTV and came up with .105 for the exhaust and .067 for the intake. The intake was tightest right after tdc...maybe 1 or 2 degrees and kept getting more and more room from there. Right after TDC is where I got my .067 measurement.
All I did this time was find where the tightest area was by looking at how much the spring compressed....I just eyeballed it. Then I took off the checking spring to let the valve drop all the way down, then I stuck my feeler gauges in as I slowly turned the motor over in that area between about 1 and 6 degrees atdc for intake and btdc for exhaust.
I am confident in my #'s now!
Thanks everyone, now the hard part is over and I can just bolt the car back together.
Thread Starter
Drifting
Joined: Apr 2009
Posts: 1,898
Likes: 9
From: Morrisville PA
I was chasing a tick noise...and decided to just tear the entire car apart. I removed both cam and lifters. I ended up finding nothing...The cam rollers and lifters looked brand new. I am thinking a lifter may have been sticking or something.
I had this cam laying around so I may as well throw it in. AI originally recommended me a 226/234, but I pussed out and went with the 226/230 thinking it wouldn't lope or smell. I was wrong on both accounts LOL, so I am throwing in a similar cam to what they recommended. A friend of mine owns a shop and I got this brand new for $200 from Lunati. It made 475 with AI heads and a ported ls2 intake manifold on an LS2 GTO, so it has been proven to make power. We shall see.
I had this cam laying around so I may as well throw it in. AI originally recommended me a 226/234, but I pussed out and went with the 226/230 thinking it wouldn't lope or smell. I was wrong on both accounts LOL, so I am throwing in a similar cam to what they recommended. A friend of mine owns a shop and I got this brand new for $200 from Lunati. It made 475 with AI heads and a ported ls2 intake manifold on an LS2 GTO, so it has been proven to make power. We shall see.
Last edited by mchicia1; May 1, 2012 at 09:57 PM.
Safety Car
Joined: Aug 2011
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From: Portland OR
You are welcome sir!
I joke a lot, but if I can give back 1% of what I have learned here, I'm tickled.
My first Vette, my first Ls engine, and I have taken this thing way further apart that I would have ever thought. Having a blast too!
Ron
I joke a lot, but if I can give back 1% of what I have learned here, I'm tickled.
My first Vette, my first Ls engine, and I have taken this thing way further apart that I would have ever thought. Having a blast too!
Ron