speedtigger

iTrader: (16)

I spent the morning installing my new camshaft, but out of curiosity I decided to check the factory preload first. This 2004 LQ9 has .130" lifter preload from the factory. I was a little surprised to see this as most of the posts that I read noted about .100" as the factory spec. I also scoured about 2 dozen different lifter preload threads and came away with the idea that ideal lifter preload should be between .080" - .100".

For comparison purposes, I also measured the base circle diameter with some dial calipers and found that the Comp XR275 measured 1.485" compared to the factory cams 1.550". This is a difference of .065". When divided by 2 I see that we get .0325" which would be the difference in lifter preload between the two on a given engine.

After installing the new cam I used the Comp Cams pushrod length checker to find 0 lash pushrod length readings varying from 7.2875" - 7.2750". This means the popular 7.400" pushrod would have netted between .1125" - .125" lifter preload. So I ran the numbers for the .025" short 7.375" pushrod and came up with a lifter preload of .0875" - .100". So, it looks like the 7.375" is perfect.

I just find it hard to believe that I needed a shorter pushrod on a camshaft with a smaller base circle to get the proper preload. Has anyone else seen a factory preload as big as .130" on a stocker?

PREDATOR-Z

Measure for correct p-rod legth, that is done with a checker. .120+ is a bit too much IMO.
don't forget those will be more agressive lobes.

speedtigger

iTrader: (16)

My new 7.375" pushrods arrived. After installing the new pushrods, I double checked my Comp Cams pushrod length tool with my old school method; a dial indicator. The results from the dial indicator verified the Comp Cams pushrod length tool. All readings were in the high 90s with the new cam and pushrods.

01ssreda4

iTrader: (96)

Something just doesn't sit well with me here. What is the length of the stock pushrods that came out of this engine? And I agree with Pred Z about not wanting to run that much preload on a harsher ramp. Factory specs are for quiet, gas mileage compliant, make the complainers happy kind of engines.

speedtigger

iTrader: (16)

The stock pushrods looked to be about 7.380", but research shows factory pushrods are 7.385". So, the pushrods I bought are about .010" shorter than stock.

Brigger18

iTrader: (20)

I'm interested in this too. I just checked my preload and its .100, I have the brute speed blower cam from comp. I removed a comp cam from the same engine. Comp recommends .030 preload if I read things correctly. I have 7.400 push rods. I didnt check preload before I removed the old cam either. Coulda, shoulda, woulda.

speedtigger

iTrader: (16)

Is this for Comp lifters? Or, factory lifters? I have not read about anyone trying to run that little amount of preload on the factory roller lifters. Whenever I hear .030" preload, it is usually by somebody talking about an old flat tappet hydraulic lifter.

PREDATOR-Z

I try to run them anywhere between .060>.080

speedtigger

iTrader: (16)

It was amazing to me that when I researched this, recommendations were all over the place. I probably read at least 25 complete threads on the topic of preload between this site and others related to Gen IIIs. The two most popular credible recommendations that I saw were between 60-80 and between 80-100. I found slightly more recommendations for the 80-100. Those recommendations coupled with the oft cited factory spec of .100" is what had me choose the 80-100 range.

Brigger18

iTrader: (20)

Here is what I just got with my new cam. Doesnt say anything about roller or flat tappet just hyd. I'm at .100 right now, I'm gonna shim mine to about .070 and see how they work. I've also read between .060 and .100.

speedtigger

iTrader: (16)

Looks like the same old standard crap Comp puts in every cam package. I had the same thing in mine. I can only say shame on them for such poor attention to detail. I think a company that claims to be valve-train experts owe their customers more than that.

Brigger18

iTrader: (20)

I didn't want you to think I was crazy.

speedtigger

iTrader: (16)

HA! Not a chance. Conversely, I think Crane Cams recommends .090".

PREDATOR-Z

Preload in our motors are dependent on p-rod length due to non-adjstable rockers. so a range is all you can hope for at best. Also if your cam is dual lobed, it might mean runing 2 different length p-rods for closest comparison on intake and exhaust.

Scoggin Dickey

iTrader: (34)

I don't understand why you would think it is sub-par for comp not to supply an actual value for lifter preload with their cam paperwork. They don't know what lifters you are running. No level of expertise can give you a value that is dependent on a different part than what they are selling you. Comp sells multiple different variations of lifters and they will supply you with recommended preload when you buy them. They can't supply you with preload information with nothing but a cam because the cam does not determine what preload you should run.

speedtigger

iTrader: (16)

That is a very understanding position you are taking. But even if they put that much thought into it, which they didn't, Comp Cams might consider saying something to that effect. Instead, they give you a generic answer that is incorrect for the cams that they are selling to the roller hydraulic crowd.

While I have been using Comp Cams when appropriate for 25 years, in this instance, Comp Cams does not appear to deserve your compassion.

They are putting out bogus data. Plain and simple.

Scoggin Dickey

iTrader: (34)

I understand what you mean.

The PC answer is this: The value they give is dependent upon abiding by their entire instructions which includes using their lifters. They mention that in order to be set up properly and maintain their warranty etc that you should use the Comp Cams recommended lifters. Any specific numbers given are in reference to their recommended lifters. In this case it would be 850-16.

Of course, there is a kink in the PC answer. If you open the 850-16 and read the instructions, it will say .045" and I don't have an answer for that .

The real answer is to follow the advise of a reputable dealer/installer from whom you purchase the parts. Then, if there is an issue, you have done it their way and that will go a long way in getting a problem resolved if you have any. I personally do .060"-.080" and I have my personal car set up at .050" for the quietest valvetrain and best performance. I'm using LS7 lifters 12499225. I never set them up over .080", they start to get noisy at that point IMO.

The less preload the better while maintaining proper preload and contact everywhere between the camshaft and the valve tip throughout the range of motion both directions, IMO.

speedtigger

iTrader: (16)

Today I tore my LQ9 down to install LS7 lifters. What I found was that the new lifters were absolutely identical to the old lifters. Same dimensions, and same appearance. This may explain the .130" preload that was measured in my stock LQ9. If LS2/LS7 lifters are .050" taller in the the plunger cup area as is often said and they did not install shorter pushrods in these motors to compensate, then we can expect all 2004 and newer LQ9s to have around .130" preload. So does this mean that all 2004 and newer LS motors have the same .130" preload from the factory? Or, did they start putting shorter pushrods in the newer motors?