Re: Optimum lifter preload
[Re: A727Tflite]
#2591357
12/13/18 04:10 PM
12/13/18 04:10 PM
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Joined: Jun 2008
Posts: 3,916 usa
lewtot184
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master
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Posts: 3,916
usa
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I see this preload topic brought up and battered to death with opinions and such.
Question for those that may have checked. How much plunger travel exists on a production Chrysler lifter? How much plunger travel exists on a late model aftermarket lifter?
Reason I ask.
The service manual calls out .060” - .210” dry lash. That equates to .040” - .140” plunger preload.
If you have production level plunger travel - your engine should not run poorly, idle poorly, perform poorly with this preload.
I ran production juice lifters in Stock Eliminator in the 70’s with a GK cam, production pushrods and rockers and never floated a valve, broke parts, etc. I kept my preload at .060”. No issues for 5 years using the same parts without replacement. Of course I only spun it 6K back then but it never failed me. all the tappets I've measured had .200+ plunger travel. this does not include any of the race tappets, just factory or OEM replacement.
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Re: Optimum lifter preload
[Re: A727Tflite]
#2591435
12/13/18 06:20 PM
12/13/18 06:20 PM
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Joined: Jan 2003
Posts: 6,416 Abilene, Texas
fastmark
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Fastmark - how did you determine how much preload you have ? What method did you use ? I used a dial indicator on the tip of the rocker by the pushrod and tightened the rocker stands until the pushrod had zero preload. The cam was on the base circle, of coarse. I tightened the bolts till the shaft was tight to the stands and then read the indicator. Comp had a different way in some instruction I had once. They said to mark the pushrod at zero preload and and then tighten the shafts and mark again. Measure the difference and you have your preload. Both methods came out the same, .110.
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Re: Optimum lifter preload
[Re: A727Tflite]
#2591442
12/13/18 06:49 PM
12/13/18 06:49 PM
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Joined: Jan 2003
Posts: 14,506 So. Burlington, Vt.
fast68plymouth
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A question for fast - in theory, wouldn’t weaker valve springs allow quicker and more violent lifter separation/pump up?
Wouldn’t weaker valve springs take longer to “pump down” the plunger versus a stronger spring? I would think so. In my case, the tired old 361 had the 100,000 mile stock single-without-damper springs...... so not much pressure.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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Re: Optimum lifter preload
[Re: fast68plymouth]
#2591475
12/13/18 08:23 PM
12/13/18 08:23 PM
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Joined: Mar 2011
Posts: 3,083 Michigan
A727Tflite
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Michigan
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A question for fast - in theory, wouldn’t weaker valve springs allow quicker and more violent lifter separation/pump up?
Wouldn’t weaker valve springs take longer to “pump down” the plunger versus a stronger spring? I would think so. In my case, the tired old 361 had the 100,000 mile stock single-without-damper springs...... so not much pressure. So in my mind ( and you seem to agree a bit ) a weaker spring would take longer to pump the plunger down - and that may be why some engines like Ron’s buddy and your 361 too so long to regain compression. Of course other factors may play in to this - condition of the lifter itself and maybe actual cranking oil pressure, would be a neat experiment.
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Re: Optimum lifter preload
[Re: lewtot184]
#2592265
12/15/18 12:13 PM
12/15/18 12:13 PM
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Joined: Jan 2003
Posts: 27,421 Balt. Md
383man
Too Many Posts
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the valve spring controls pump-up, not pre-load. reducing pre-load just reduces pump-up distance. Yes but the point here I believe is if you run the lifters with almost no preload even if you over rev the eng the lifters cant pump up enough to hold the valve off its seat. I have seen that a few times over the years on stock type engines. When I worked at a used car dealer I ran a 351 Mustang real hard on a road test and the lifters pumped up enough to hold the valves off the seats and stall the eng. I had to wait a bit before it got comp back. That's why I ran only about .010 preload in my old 383 since I raced it sometimes and used basically the stock valvetrain with Comp single springs. Course to close to no preload and it has more valve train noise. But I understand what you mean also about the spring tension making a difference if you run the normal preload. Ron
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Re: Optimum lifter preload
[Re: fastmark]
#2592266
12/15/18 12:15 PM
12/15/18 12:15 PM
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Joined: Jan 2003
Posts: 27,421 Balt. Md
383man
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Too Many Posts
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Balt. Md
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Most stock lifters will pump up and hold the valves open at the upper RPM if they have to much preload, setting the preload from .010 to .030 hot will help stop that I keep going over this I’m my brain and I think this is has got to be the case. The higher the rpm, the more they will pump up. The more room they have to pump up, the more like they are to hold open the valves. Basically your right but the stronger valve springs will fight against the lifters pumping up and holding the valves off the seats. Ron
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Re: Optimum lifter preload
[Re: A727Tflite]
#2592705
12/16/18 12:30 PM
12/16/18 12:30 PM
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Joined: Nov 2003
Posts: 36,041 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
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Lincoln Nebraska
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Fastmark - how did you determine how much preload you have ? What method did you use ? What I do is: with it mocked up, put a swath of dykem on the pushrod, then slide a thin flat razor blade over sideways from the valve cover flange on the head & make a slight mark in the ink then undo the rocker to let everything raise up till the cup "just" reaches the snap ring then make another razor mark then measure the distance between the (2) "marks" on the pushrod.
live every 24 hour block of time like it's your last day on earth
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Re: Optimum lifter preload
[Re: RapidRobert]
#2592733
12/16/18 01:27 PM
12/16/18 01:27 PM
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Joined: Jan 2003
Posts: 6,416 Abilene, Texas
fastmark
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Posts: 6,416
Abilene, Texas
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Fastmark - how did you determine how much preload you have ? What method did you use ? What I do is: with it mocked up, put a swath of dykem on the pushrod, then slide a thin flat razor blade over sideways from the valve cover flange on the head & make a slight mark in the ink then undo the rocker to let everything raise up till the cup "just" reaches the snap ring then make another razor mark then measure the distance between the (2) "marks" on the pushrod. I’ve done it this way before. I got the same measurements both ways. I fixed the problem yesterday without buying adjustable rockers at he customers request. I settled on .035 to .045 using Shim’s under the stands. It was a royal pain. Way too time consuming just to save the customer money and be a one time fix. I had to use more shims at one end of the drivers side head. Better than .110 to .145 preload though.
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Re: Optimum lifter preload
[Re: fastmark]
#2592748
12/16/18 01:47 PM
12/16/18 01:47 PM
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Joined: Dec 2004
Posts: 10,555 Rittman Ohio
fourgearsavoy
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I had to use more shims at one end of the drivers side head. Better than .110 to .145 preload though. That just doesn't sound like a good solution to me Wouldn't that stress the shaft? I wouldn't sign off on that repair Gus
64 Plymouth Savoy 493 Indy EZ's by Nick at Compu-Flow 5-Speed Richmond faceplate Liberty box Dana 60
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Re: Optimum lifter preload
[Re: fastmark]
#2592763
12/16/18 02:14 PM
12/16/18 02:14 PM
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Joined: Jan 2003
Posts: 14,506 So. Burlington, Vt.
fast68plymouth
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I Live Here
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So. Burlington, Vt.
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Aaaaahhh yes........ the old “stand splitters”, er...... I mean shims.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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Re: Optimum lifter preload
[Re: fast68plymouth]
#2592783
12/16/18 02:57 PM
12/16/18 02:57 PM
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Joined: Nov 2003
Posts: 36,041 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
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Posts: 36,041
Lincoln Nebraska
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I dont have the last word on this but it recollected something about custom shims that someone offered that are thinner on the "sides" to counteract this.
live every 24 hour block of time like it's your last day on earth
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