A few years ago when I did my heads/cam I set my lifter preload to .075". The valve train has always been a little noisy, much more than I would care for.

Back when I came up with .075" preload I spent A LOT of time researching the correct preload to run...a lot. The numbers were all over the map .010-.100. Depending on the time of day, when you call Comp Cams they tell you .030-.040 to .080-.090.

I'm in the process of installing new rocker arms so I'm going to take the opportunity to check the pushrod length again.

What pushrod preload should I be using? Does more preload reduce valve train noise or does less preload reduce valve train noise? I've read arguments for both.

BTW: 228/232 .571/.573 112

Thanks for the help! I really really appreciate it.

 

I've been searching the web for a while and here is what I've found:

stock .060 - .120 preload
850-16 .030 - .050 preload
comp R .004 -.010 preload

This is "hot" preload so you can expect to lose .010" from the head/block expansion.

A lot of people are running the 850-16 lifters and a lot of people complain about excessive valve train noise. Comp Cams does a horse crap job of explaining the lifter preload requirements of their lifters and everyone generally assume O.E. specs.

From what I've read, too much preload results in excessive noise as the pushrod is bottoming out (at lower RPM and oil pressure). However, I don't think this is the case. A lot of people (myself included) don't have much in the way of excessive noise until AFTER the motor warms up. Thus, it would seem that the noise is a result of too little preload NOT too much preload. This is because .010" of the cold preload is "lost" when the motor warms up.

My preload is .075" cold or .065" hot. If .075" is quiet and .065" is noisy it would seem I should have a preload of .085 cold (so its .075" hot). However, if the .030"-.050" of preload is correct, .075"-.085" seems like it would be way to much preload.

Any thoughts? Pro engine builders, what say you?

 

Is anybody running the comp 850-16 lifters?

 

I always use the 875-16

 

What are you running for preload on those? Comp Cams says those need .003-.010.

 

I don't have the answer you are looking for but would suggest you find out which company makes the lifters for Comp. That would be a better source of information on where to set the preload. I highly doubt they actually manufacture the lifters in house and there are only a few manufacturers to begin with.

 

the first time I just used stock pushrods. This time I am getting custom pushrods due to the cam and milled heads. I was looking at .010, but was going to call Comp and verify what the lifters want. I know with the LG G5X3 and those lifters I had ZERO lifter noise with stock rods.

 

Great idea!

I'm a little frustrated with Comp Cams right now. Depending on who picks up the phone over there you get a different answer.

I'll see if I can get that info out of them. I would really like to solve this mystery, and I'm sure many others would too.

 

Maybe I stand corrected. See link below. Given the information in the link, you may want to contact their engineering department. I have had no luck in the past with their tech support. In fact, they told me something once that would have ruined my motor had I followed their advice

 

So I called Comp Cams and the tech sounded like he knew what he was talking about (it didn't sound like he just came off the street when they threw the "help wanted" sign up in the window). He told me I should shoot for .043" but .043"-.060" is what I want. He also told me that the lifter has a total travel of .160", which I believe is exactly what the stockers have. I think I remember determining that as well when I was determining the preload that I currently have (.075").

Here's the deal. My valve train is quiet when the engine is cold. Its not until the engine warms up that the valve train get noisy. I only really notice the noise when I slowly accelerate in 1st gear (up to 4000+ rpm, for example). At that point the valve train sounds "loose", is the best way I can describe it...and it drives me crazy. So, to me, it seems that there are two important variables at play here. 1) lower oil pressure and 2)lost preload (.01") from engine expansion.

My gut feel tells me I want a little more preload to account for the lost preload when it gets hot, but the tech thought that would not be a good idea as you can damage the internals with too much preload. But how much is too much? He also seemed to believe that the valve train would quiet down with less preload, but why is it quiet when the engine is cold?

He also said that with my cam (228/232 .571/.573 112) the valve train is going to be noisy. But, again, I ask why is it not noisy when its cold?

Has anyone ever quieted down the valve train by reducing the preload? I can buy that lifter can suck in more oil if it has more travel and, thus, have more cushion. But again, I ask, why is it quiet when its cold as the lifter has more preload when its cold.

Yella Terra says I want .060"-.090". Of course not all lifters are the same (if you tried that on caddy lifters you'd likely destroy the valve train. But why is yella terra recommending something that the comp cam tech told me would destroy the lifters?

Does anyone trust the techs at Comp Cam? Holy crap is this frustrating.

I have more $ than I do time. If I could I'd try every combination to see what worked, but I just don't have the time.

Thanks for all the help! Any thoughts/experience would be greatly appreciated!!

 

I haven't heard any LS engines with aftermarket cams that have "silent" valve trains.
Maybe it's a relative term.

My LS1 with an EPS cam, ls7 lifters, and YT rockers is also pretty quiet cold. Certainly not silent, but quiet. When fully warmed up it makes a decent racket.
I set the preload to .060 cold.

My L33 (alum 5.3) with a similar cam from Tick is much quieter. It uses stock rockers with trunion kit. It also makes noise when warmed up, but not too bad. Most noticeable right around 2300 rpm. Same preload.

Noisier hot tells me the lifters bleed more when hot and the oil is thin.

Folks have used the fancy Johnson lifters with good success. Bring your checkbook.

Btw, the YT rockers make noise too. When I replaced my busted YT's with the new design, it was certainly quieter.

A bunch of words with no answer. If convinced it's preload related, try a couple different sets of pushrod lengths and see what happens.

Ron

 

Pushrods are easy to change out, so take Ron's advice.

In the 3 motors I've done H/C on, I've set them all in the .025-.035 range.

All with LS7 lifters and stock rockers with the trunion upgrade.

I haven't noticed excessive valve train noise. I spin/spun each of these motors to 6800 rpm+

 

Thanks guys.

Yeah, I think what I'll do is to get a couple sets of pushrods. One for around .05" and the other around .085 (as I'm already at .075"). Then I'll sell the pushrods I don't use!

 

Not sure what oil you are running, but that might have some effect as well. Mobil-1 is thin once hot. Wondering if an oil with higher viscosity at 100 degrees C would quiet things down before going back into the motor. German Castrol 0W30 (now made in Belgium) is high within the 30W range and might be a good oil to try if you can find it locally.

 

I don't run walmart oil (Mobile-1) in my vehicles. I have been running Royal Purple 0w40 but I think I'm going to give the Royal Purple HPS oil a try.

I'm going into the motor anyways to install the rocker arms so I think I'll take the techs advice and try less preload, but I'll also have a set on hand that slightly more preload than I'm currently running if the shorter pushrods don't seem to help.

 

any of you have experience running 875-16? Trying to decide what preload I want to shoot for...

 

Those don't require much preload at all, something like .006-.010. Since pushrods generally come in increments of .025, unless you get lucky, or can use shims, you'll likely need adjustable rockers to achieve that.

 

Would you all agree that if you have a decent size cam and you claim not to have valve train noise that you are either a) deaf or b)lying?

 

By the way, comp cams tech support is useless. They either have no idea what they are talking about or lifter preload can be anything and it doesn't matter. I've called them 3 times and each time they tell me something different. Today it was .018-.025, the other time it was .043-.060, and another time it was .020-.040. Thus, it looks like a preload of .018-.060 is ok, if they have any idea what they are talking about.

 

I'm going to be running 7.375 pushrods with my 875-16 lifters. They will give me approx .022" preload. With no preload I need a 7.353" pushrod.