I am looking at using a Comp Cams Extreme Energy flat tappet cam in my 1985 305 LB9 TPI. Specifically 12-256-4 that they recommend for TPI. I have seen internet comments about higher valvetrain noise than stock with this product series in general, and Comp Cams tech people reference possibility for some "sewing machine noise" because of higher valvetrain velocities.

My question is:
1. Have any of you used this cam and what is your opinion of the noise? Noticeable? Normal?.
2. Has anyone seen evidence of timing retard or knock counts generated by the valvetrain?

 

I previously had the same cam in a 350 with tbi. Yes it was noisier than stock. No, I did not have a knock detection issue. The noise drove me bonkers though.

 

Cant say ive seen much difference in knock counts with some aggressive cams. Xfi stuff has been very noisey and didnt seem to do much for knock on 2 combos i tuned. My own personal big cams didnt seem much different either

 

I have had a magnum high lift and lunati bootlegger with rhoads lifters. Never had a knock count issue. On the other hanf I had a comp 4x4 extreme roller a few years ago that was terrible.

 

If the noise bothered you, was it the intensity or the type of noise? Can you give an idea how loud it was?

 

I was asking because I had an experience once with a 305 that had some valve lash. Bad adjustment on a hydraulic cam, running like a solid lifter cam. The knock sensor was picking it up and causing an erratic huge retard--on the order of 20-30 degrees - closed throttle at idle or fast idle. The timing was swinging all over the place. So, if the Comp Cams grind is noisier, it would seem possible to get a knock sensor reaction. So, very interesting that you had that response with a roller cam. They market the one that I am considering (XE256) it for computer controlled SBC, so one would think it should work. But I would rather not have to change it out or tinker with the knock sensor calibration. I also am concerned if the base design is noisy, so perhaps I should be looking for a different design. The idea of pushing the area under the lift curve with higher velocity valve action seems reasonable, but perhaps these are exceeding reasonable limits.

 

I have a Comp Cams 260XFI HR-13 and on the street I have had a problem with knock counts. I have tried moving the sensor to the end of a 90 deg street ell to help cut down the sensitivity of it. On a 20 minute track session it's not uncommon to have more than 10,000 knock counts. I have ended up disabling the knock retard and go with reading the plugs to ensure I do not have too much timing on the motor.

 

My bone stock 91 z28 had all kinds of timing retard and knock counts on factory stock motor. I pulled 10 deg and put 93 in it and still got retard. I chalked it up as false and did what i could to disable the sensitivity and amount of timing it could pull. Sometimes they can act up. Not necessarily true knock. Always something to watch for

 

Sounded like my lifters were out of adjustment all the time. Didn't matter how or where I adjusted them, running, half turn, 1/4 turn, full turn. Constant lifter tick.

 

same as alcee cant stand that line..plus they all went flat fast..had an XFI 280 that lost lobes prior to 15k washed my hands of that companys stuff.
Not worth afew lbs tq.

 

on a flat tappet right? Not the rollers? I’ve heard this on comps flat tappets thats why i would never run a flat in a modern motor