Does anyone have experience with comp cam pro magnum lifters? On my recent engine build, I installed comp cams xr300hr hyd. roller cam, the pro magnum lifters and roller rockers. I feel like I can't get a straight answer out of comp cams regarding preload. Telephone tech support and my builder identify 0 lash/no pre-load. The tech tips on the comp cams web site says .002-.004 preload which I believe is about an 18 degree turn. These things are as noisy as my solid lifter motor. Some friends whose advice I respect recommend preload. Anybody in maryland want to give it a listen in the next couple of weeks? The engine (454, rectangular ports) runs like a scairt dawg. Pulls very strong up to 6100 rpm.
Thanks for advice in advance!

My guess would be the combination of an agressive ramp and an anti pump-up lifter. Even though the Comp XR rollers are not real high lift cams, the lift intensity is supposed to be fairly high. The Comp XE line of hydraulic flat tappets is known to be noisy just the same.

??? Possibly , like the XE line, you're hearing the exhaust valve slap the seat on closing. ??? If so, get used to it. No adjustment will help. Its the way they are.

I have that same cam in my 498". Which valve springs did you use? They recommend the 924-16. I feel they are a bit soft for that roller cam. They recommended the same springs for my xe284 flat tappet hyd.

They only recommend a 911 for most hydro rollers. As a comparison, Lunati only recommends single springs for their hydro rollers, including the .600 lift cams. Too much spring is as much of a problem with hydra rollers. The noise is most likely a result of the fast seat ramps of the Extreme Cam series.

Thanks for the responses, most appreciated. At this point, I'm leaning in agreeement with 427L88. But, Chevywidow: I don't recall the spring specs. I believe they were matched to the cam. They are dual springs. I will find out. I am considering putting some pre-load on the lifters this weekend. There is none currently. My math indicates a 7/16x20 thread .002-.004 turn is about a 9 degree wrench turn, which is almost nothing. I can still spin the push rod currently between my fingers. The car runs and sounds fantastic, it's just much noisier than any other hydraulic roller cam valvetrain that I have heard (I do not claim to have heard lots of them, either)
Thanks in advance for any additional thoughts or assistance

Maybe I'm missing something, but why would this motor be any different from other hydraulic cam motors running 1/4 to 1/2 turn of preload?

I dont understand why Comp would tell you to not run any preload....

Originally posted by MY FYN 79:
Maybe I'm missing something, but why would this motor be any different from other hydraulic cam motors running 1/4 to 1/2 turn of preload?

I dont understand why Comp would tell you to not run any preload.... =
It's the design of the lifters & it is a hot setting. The preload is .002-.004 hot.
This is how they try to get the engine to RPM with aggressive lobes. :D
BTW, you don't want to run more than about 360lbs or so on those cams for any extended use, they are a casting not a billet.

I truly appreciate the comments and advice. I intend to adjust the valves this weekend. They are cuurently 0 preload, I am going to go for .002-.004 which should be less than 1/16 of a wrench turn by my calculation of 7/16x20. Once again, Thanks guys, I'll post the results!