Havoc40

The preload debate regarding noise is really just a fight with sizing and grinding issues within the internals of the lifter bodies themselves. Some quiet up with more preload, some less. When the parts are ground straight (no taper) and sized properly, you don't have a single point controlling the valving of the lifter. That single point causes many problems once temperatures rise to operational levels. Many of those problems include noise, as well as not achieving full potential of the cam profile. When you have a straight lifter bore and piston as well the components being sized properly, preload becomes moot when regarding noise and is more about performance.

Having .002-.004" preload is not acceptable for "preload" IMHO. Think about thermal expansion here, especially in an all aluminum LS engine. Do you honestly think after engine temperatures increase, the .002" preload is going to remain? Answer is no, you'll have a few thou lash.

There is nothing to gain from running the piston down .100" on OEM parts, unless your trying to band-aid a noise problem. Valve float would have to be severe in most cases to cause contact from over pump-up, but it has happened before.

FWIW LS7 lifters have an average total travel of about .200", give or take GM's allowable tolerance window.

speedtigger

iTrader: (16)

Wow. That is more than I would have guessed.

ZeeOSix

The chart I posted shows the current LS7 lifter (GM p/n 17122490) to have a total plunger travel of 4.22 mm = 0.166". Not sure where the 0.200" came from. Did someone measure it?

speedtigger

iTrader: (16)

I don't know about that chart, but I am willing to bet that Havoc measured.

RonSSNova

iTrader: (3)

So in a lifter that is machined correctly, (the bore in the lifter body), preload should work anywhere from .010" to .100" with the lesser value preferred from a performance standpoint.

The lifters with issues would have to be tapered with the bottom in spec and the top out of spec. Interesting.

So the bleed down rate is plunger location specific. Hence folks trying all kinds of different preloads to shut them up.

BigBirdLS1

I am soooo glad that my XE-R lobed cam is quiet. If I had noise like the OP I'd never drive my car I'd try anything to get it quiet. Hope those new lifters fix the issue.

dr_whigham

iTrader: (49)

Am I the only one who's not in the preload pissing contest that wants to know who the lifter manufacturer is?

DrkPhx

iTrader: (15)

OP - That sounds terrible; much worse than the usual sewing machine sound. What was the length of the pushrods when you ran the LS6 cam and LS7 lifters? I ask because the LS6 cam has a smaller base circle than the stock LS1 cam which requires a different pushrod compared to stock.

salemetro

iTrader: (5)

As measured with a pushrod length checker, and verified w/dial calipers.7.295 gave me zero lash. ..7.375 length gave me .080 preload (first set of pushrods). Now, there's 7.350 (.055) in the engine, and no change.

thunderstruck507

iTrader: (18)

Stock ls1 is ~7.4" and I thought the ls6 cam used ~7.425"

Is it possible there was an error measuring? It's apparently easy to do...I did it wrong. Did you double check by counting turns too?

3pedals

iTrader: (3)

That's the way I like to check PR length, and I beleive .030 - .050" is correct.
Hope the new lifters work out for you

salemetro

iTrader: (5)

I get what your saying....but no. Measurements were dead-on.

I've decided....for sake of a fair comparison....to just pull the heads and replace the lifters. I'll be leaving everything else the same for now....cam, springs, etc. That way, there should be no debate as to what the root cause of the problem is. I'll install the new cam and springs in a month or so, but should get to changing the lifters in the next week or so.

RonSSNova

iTrader: (3)

This is also how I'm doing it. No counting turns. Just direct measurements.

I was unable to get the used lifter apart. so I'm letting one soak in brake clean to thin the old oil.

Ron

5.3LJimmy

iTrader: (10)

LS6 Camshaft - 204/218 .551/.541 117.5 LSA Please note that this cam has approximately a 0.050" smaller base circle than a stock LS1 camshaft. This smaller base circle will require longer pushrods for applications with stock length valves and no milling for the head surface.

^^^ That is from Thunder Racing's site and I agree after installing a couple LS6 cams that the base circle is 0.050" smaller. If all other components are stock then the correct pushrod length is 7.450" when running an LS6 cam.

salemetro: I think you are running a pushrod that is way too short. That noise is excessive and is obviously coming from more than a couple lifters. There is an issue with your preload, not the lifter choice.

thunderstruck507: The LS6 had the same pushrod length as every other gen 3 engine. The LS6 specific valves are longer to compensate for the smaller cam base circle. Also if you are running stock gaskets and a stock head milled .010" then you should be running the 7.4" pushrod.

It may be good practice to measure pushrod length but in alot of cases it causes more harm than good. I have seen quite a few folks that measure and end up with the wrong length for their engine.

joecar

Also, do the LS7 lifters have the cup located 0.050" higher than the LS1 lifters...?

if so then using LS7 lifters with stock LS6 heads/cam and stock gaskets results in a net shortening of required pushrod length.

thunderstruck507

iTrader: (18)

That sounds like creating extra work for yourself to please us internet browsers, I didn't mean to imply I thought you should do such a thing it was just a thought that the combo as a whole versus 1 part could be to blame.

Thank you for clarifying, I seem to recall now reading the ls6 valves had longer stems.

salemetro

iTrader: (5)

[QUOTE=5.3LJimmy;16053872]salemetro: I think you are running a pushrod that is way too short. QUOTE]

Something to consider, is that the heads have been milled, and I'm using aftermarket head gaskets (I didn't check compressed thickness)...also, there are 2 different height LS7 lifters that have been produced over the years...varying from each other by .050. I'm not sure which "batch" mine are from, but I would assume they are the taller ones. Additionally, I'm not sure if the comp trunion kit would change rocker installed height at all (can't imagine that it would). From looking at it, the swipe pattern looks normal. Also...it's an L33...so should have the same lenghth valves as the LS6...correct?

I get what you're saying, but I have verified the measurements 3 different times, as well as checking (for the hell of it) installed spring height. 7.295 has been the repeated zero-lash MULTIPLE times. Don't know what else to say here....except that I've been over it a few times, with the same result.

I'll be tearing into the car tonight after work, and finishing over the next few days as time allows. I'll be using OEM head gaskets this time, and won't be changing the cam out yet.

salemetro

iTrader: (5)

No worries....it's more to put to bed any potential "unfair comparison" claims. Not to mention, a cam change will be easy to do in the near future.

RonSSNova

iTrader: (3)

If he did a direct measurement of the adjustable pushrod set to 0 lash, with his combination of parts, added the desired preload to the length, how could he end up with pushrods that are too short?

i'm going to assume he had the cam on the base circle and not on one of the ramps. Beyond that, it's not rocket science.

kenp

iTrader: (9)

I don't disagree with you, and in my install I included the assumption that I would lose approx .010" to thermal expansion. If you do the install and everything is at 70* F and you assume 220* F temps fully warmed up, there's a 150* F differential. I'm no mettalurgist, but near as I can tell, aluminum expands about 13 micro inches per *F and steel expands about 8 micro inches per *F. 150 X 13 = 1950 micro inches of expansion for the aluminum, and 150 x 8 = 1200 micro inches. one micro inch = .000001". The aluminum would expand approx .000001 x 1950 = .00195" and the steel would be approx .000001 X 1200 = .0012". .00195" - .0012" = .0075", so, there may be a loss of about 7.5 thousandths of an inch. I set my cold pre load at .012" so that should have me in the .004 range fully warmed. I've been running the comp "r" that way for 3 or 4 years now w/o issue. That's the way I did it. Works for me. That's all I can say about it.