Odd Lifter preload issue/question
Thread Starter
Burning Brakes
Joined: Apr 2010
Posts: 753
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From: Spring Hill TN
Odd Lifter preload issue/question
Hey all i have a z06 with tfs 215s and a g5x3 cam and lunati shaft mount adjustable rockers. Heres my question I recently switched from comp cams 5/16s to 3/8s pushrods 7.500 length. With the 5/16s pushrods i was running a turn and a half preload .090. Since I changed the pushrods the max preload i can run is about 3/4 turn about .045. Im running ls7 lifters and pac 1521 springs shimmed to spec. Anything more than .045 and the car is hanging the valves open and wont idle.
The only change was the pushrods is there any reason why the stiffer pushrods need a different preload? flex maybe? The car is running fine i was just curious as to what would cause this.
Thank you in advance for the replies.
The only change was the pushrods is there any reason why the stiffer pushrods need a different preload? flex maybe? The car is running fine i was just curious as to what would cause this.
Thank you in advance for the replies.
Burning Brakes
Joined: Mar 2010
Posts: 1,189
Likes: 4
From: Freeport, FL
Pushrods alone will not have an effect on the preload.
Heck, .045" is enough preload and will lessen the chances of lifter "pump-up". Strange about the change, but it sounds like everything works just fine.
I'd be curious to hear what the cause is, if you found out what was really going on.
Heck, .045" is enough preload and will lessen the chances of lifter "pump-up". Strange about the change, but it sounds like everything works just fine.
I'd be curious to hear what the cause is, if you found out what was really going on.
Thread Starter
Burning Brakes
Joined: Apr 2010
Posts: 753
Likes: 0
From: Spring Hill TN
Pushrods alone will not have an effect on the preload.
Heck, .045" is enough preload and will lessen the chances of lifter "pump-up". Strange about the change, but it sounds like everything works just fine.
I'd be curious to hear what the cause is, if you found out what was really going on.
Heck, .045" is enough preload and will lessen the chances of lifter "pump-up". Strange about the change, but it sounds like everything works just fine.
I'd be curious to hear what the cause is, if you found out what was really going on.
Last edited by BHRZ06; Oct 21, 2010 at 07:48 PM.
Burning Brakes
Joined: Mar 2010
Posts: 1,189
Likes: 4
From: Freeport, FL
I havent and the rockers are a tad noisy compared to before definitely has a sewing machine noise now. If i tighten it at from where its at it hangs the valves open. The car runs great though very strong. I just found it really strange. I changed 1 cylinder back to 5/16s for fun and it takes .090 with the 3/8s .45 is the max any more and it wont run. The noise is a bit annoying but i guess ill get used to it
So, at one setting it doesn't allow the valve to close ("hangs the valves open"), but when you tighten the adjuster on the rocker arm to add more preload it then allows the valve to close??? Seems reverse from what should happen.
I'd be curious to see pics of the set-up.
Well, I hope you get it figured out
Thread Starter
Burning Brakes
Joined: Apr 2010
Posts: 753
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From: Spring Hill TN
Not sure if I understand...
So, at one setting it doesn't allow the valve to close ("hangs the valves open"), but when you tighten the adjuster on the rocker arm to add more preload it then allows the valve to close??? Seems reverse from what should happen.
I'd be curious to see pics of the set-up.
Well, I hope you get it figured out
So, at one setting it doesn't allow the valve to close ("hangs the valves open"), but when you tighten the adjuster on the rocker arm to add more preload it then allows the valve to close??? Seems reverse from what should happen.
I'd be curious to see pics of the set-up.
Well, I hope you get it figured out
Thanks for the input man i found this extremely odd
Burning Brakes
Joined: Mar 2010
Posts: 1,189
Likes: 4
From: Freeport, FL
It is strange. All I can say is that there most be some kind of interference using those pushrods. Can't think of what the interference would be though
Thread Starter
Burning Brakes
Joined: Apr 2010
Posts: 753
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From: Spring Hill TN
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Thread Starter
Burning Brakes
Joined: Apr 2010
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From: Spring Hill TN
Thread Starter
Burning Brakes
Joined: Apr 2010
Posts: 753
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From: Spring Hill TN
Team Owner
Joined: Mar 1999
Posts: 22,025
Likes: 192
From: At the beach in little Rhody
Found it, read the entire thread. Erik is "Racer7088". Link
Last edited by vettenuts; Oct 22, 2010 at 05:21 AM.
Former Vendor
Joined: Apr 2006
Posts: 2,470
Likes: 2
From: Portland OR
St. Jude Donor '10-'11-'12
Here it is without the commercial post in the middle of it:
We offer HKE pushrods 11/32 and 3/8's, what ever length you need
I use 11/32 on TFS intakes and 3/8ths on exhaust as that all that will fit the bigger heads with the port moved over. We've used larger but we had to modify the heads. The smaller and older heads can run 3/8ths on some depending on rockers.
As always you have to check first. Get 1 3/8ths and then check.
As always you have to check first. Get 1 3/8ths and then check.
We offer HKE pushrods 11/32 and 3/8's, what ever length you need
Thread Starter
Burning Brakes
Joined: Apr 2010
Posts: 753
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From: Spring Hill TN
I would suggest double checking this. Erik at HKE has made a few posts recently where he has found the 3/8" pushrods make contact even though the newer heads are machined for them. When I did mine I used machine blue and coated the pushrod then spun the motor with no spark plugs to keep pressure on the lifters. I can't remember where Erik said this problem occurred but if I find his posts I will link it.
Found it, read the entire thread. Erik is "Racer7088". Link
Found it, read the entire thread. Erik is "Racer7088". Link
Le Mans Master
Joined: Jan 2009
Posts: 6,226
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From: Morton illinois
St. Jude Donor '14-'15
what is suggested preload on a LS7 lifer? My caddys are .60, and I thought the LS7 were about the same...have you checked spring height as well? my buddys VT was being noisey and broke some rockers...turned out it was the wrong size valve seat...and you sure 7.5 is the right PR? 7.5 is pretty long..what CC are your heads?
Le Mans Master
Joined: May 2005
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From: Fort Lauderdale, Florida
Thread Starter
Burning Brakes
Joined: Apr 2010
Posts: 753
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From: Spring Hill TN