Excellent post here guys, Mindgame

I have a buddy who recently rebuilt his motor, and its just not running right, but I think they were going 1/4-1/2 past with the comp-rs.. I just forwarded this to him, and if not on his own, by next weekend when I am down there I will do it for him and see what the results are. His valve train is noisy and he feels like hes "losing power" alot faster than he should be. Hopefully the 0-ish(haha) lash diddly will fix it.

I'll keep you guys updated and see what I/We can come up with.
Great info. (I'll soon have the Comp-Rs in my motor in the next weeks when I button her up, so Im very glad I found this thread!)

 

When I do my rocker adj., I slowly tighten the nut down until the rockers arm doesnt chatter anymore. This should be fine right? The pushrod end slapping the rocker arm is what I am listening for. Any opinions or advice??

 

Since the Comp recommended spec is cold w/o the car running I
would think it's the best approach. I agree since the determination
of zero lash with the car running is nearly impossible to identify. There
is just too much going on with the engine running to accurately set
the lash. I have set hydraulic lifter preload using the cold w/o engine
running method for 25 years. It works great and is a lot easier too.

 

Actually there website says with the engine warmed to normal temp.

http://www.compcams.com/Technical/Cu...ML/282-283.asp

 

Comp R`s are set cold, regular HE lifters hot.

 

I just did a H&C install with comp R's and 7/16th studs this weekend..

I did 1/16th of a turn past zero..

No problems here at all.. noise is fine revs freely..

I was pretty scared about lashing these things after looking at all the threads I guess I was just lucky, or careful.

 

says who? Did you read the tech tip on there web page?

 

The link you posted does not list comp r`s unless I`m missing it. It lists the HE`s.

 

Your missing it.
The "r"s that you refer to are the 875-16 lifters which are called Pro Magnum hydraulic and in the tech tip right below the description it says
"Pro Magnum lifters must be installed on an engine with adjustable rocker arms and preloaded to .002-.004" Always set the preload with the engine warmed to normal operating temptures to allow for thermal growth."

 

Your right I was just looking at the wording pro magnum, did not look at the part numbers. I was looking for Comp R wording. Of course that does go against what most people on here have posted they were told by comp cams help line.

Thanks for the point out though.

 

Some of the Mustang guys on the mustang forums actually set their lash about 25 thousandths LOOSER than zero lash. You get some ticking but apparently you make more power.

I have Comp R lifters with a cam similar to the GM 847. The cars pulls very hard to 7200rpm with my valve lash set 25 thousandths looser than zero lash. 116mph traps so far. I'm going to dynotune the car in a couple of weeks with PCM for Less.

Any comments? Am I doing something wrong or harmful?

 

It has always been said that "looser is faster" in regard to hydraulic lifters. If your car is mainly for race or limited street, no problem. If it's a daily driver, you probably want a little preload to keep things quiet. YMMV.

 

I have true duals with dynomax bullets. I can't hear the sewing machine under the hood.

My mechanic set the rockers on his supercharged 540 V8 25 thousandths looser as well. He says it makes the car think there is a bigger cam in there than there really is.

 

Well cool, they recommend the preload settings HOT. Never mentioned that in their old catalogs but I'm sure they got tired of answering the question, thus updated.

FWIW I have been setting them just as I described and haven't had an issue yet. Like I said, play with it at the track and see what you find.

-Mindgame

 

Grip,

Whether you're doing anything harmful or not is anybody's guess. Just keep a close eye on things and play with the settings somewhere where you can really quantify gains/losses. The track or a dyno is as good as it gets.

I do remember reading some tech from Chapman Racing Heads some time ago where they talked about tighter lash sometimes helping power and how it seemed counterintuitive, but the bottom line was that some valvetrain setups just did better with a tighter setup. Testing on a Spintron was showing them that the lash had a very definite effect on valvetrain harmonics and in this case, the tighter setting yielded better dynamics.

edit:
Worth noting is the fact that Chapman was working with a mechanical cam, not a hydraulic. I don't doubt that harmonics could be effected with either though.

-Mindgame