[Tom Cheatwood]

Has anyone made a change to the Comp. Xtreme energy cam? If so,what cam were you using and what kind of gains did you get from the Xtreme grind in your 455? I'm thinking I might make the change this winter.
Tom Cheatwood

[Tom Cheatwood]

Has anyone made a change to the Comp. Xtreme energy cam? If so,what cam were you using and what kind of gains did you get from the Xtreme grind in your 455? I'm thinking I might make the change this winter.
Tom Cheatwood

[Skip Fix]

Tom, I think Lee Atkinson has tried one. I have one I had ground for my original 78 400(now siting in an 81 project TA). The seat duration is not exactly what they advertise even checking it at the correct lobe lift theycarry about 6 degrees more seat than they say.

From looking at the lobes and the duration at .200 they look like a good quick ramp design similar to the Ultradyne. Add in the correct seat duration and they are about the same. Their newest catalog has some even newer lobes in it.

My 400 has a 262/270(per Comp) 218/222@0.050 I had ground on a 112 for this 9:1 400. Waiting for the rest of the exahust to get hooked up to drive it some.

[Michael G]

Tom, I didn't want to respond to your question because 1. I am not running a 455 and 2. I did not make a change from another cam.
I've spent the season running the cc 268 EE cam in my 428 and will be pulling it this winter. Other then possibly being the reason for not achiving my performance goal, I do not want to work with it because it has to be
one of the noisiest cams i've ever ran. I first thought the problem was with my 1.52 cc roller tips. I tried a set of stock rockers with no change.
After reading a related post from Will I am conviced the problem must be related to the fast ramp lobe design. Also not knowing the effects of the faster ramps on the down side on my non hardend valve seats I've decided it's got to go.
My 2 cents and something to think about.
Maybe some more opinions from others running this cam will back up my suspicions.

[Will]

Michael G, what lifters were you running with it?

I naturally assumed all the racket mine was making was due to the Rhoads lifters I had on it. Haven't heard complaints of excessive noise from other folks running them with regular lifters. Very interesting... I was also running the Comp roller tip rockers and more than half of the roller pins worked their way loose in the rocker body. Don't know what's up with that...

Anyway, I went to the CC XE274 from a custom Comp grind based on the 280-9 magnum lobe that was a single pattern, 232 @ .050" and 112 lobe sep. The old cam was installed at 111 intake centerline and had 1.7 ratio roller rockers on it that were causing coil bind problems. I replaced that setup with the XE274 and the 1.52 Comp roller tips and the engine picked up a lot of power. Never got it to the track with the first setup and really wish I'd just left that cam in there, advanced it 4 degrees and switched rocker arms to fix the coil binding problems. The XE274 had a very lopey idle in my 400 and came on strong above 3500 RPM. In a 455 I'd expect it to be a bit mellower and the power to come in closer to 3000 RPM. If you really wanted to tame it some and get the torque in earlier, do what Skip did and get it ground on a 112 lobe separation with the intake at 107. That would be a mean cam in a 455...

[Michael G]

Lifters I am using are the Summit brand which I believe are made by crane. The next set will be CC to be on the safe side.
The noise sounds more like spark plug wires arcing to ground. Even turned off the garage light once just to check.
Picking the right cam for all the right reasons has never been one of my strong points. All I know is the RA-IV style cam is a hard one to beat and I think I can spin one fast enough to make it work. Wheather I can flow the air will be another story. At least now I have some times to compare it to. Timeslips don't lye. Mike

[Skip Fix]

I have tried all types of lifters on fast ramp cams and they all have valvetrain noise. I agree it is probably from the ramp design, never caused problems but they are a little noisier.

[77TA]

I have the EX274 in my 455. It ran 13.7@ 103 with restricted secondarys and with it cutting out in 3td and 4th gear on a 100 degree day on a very slick track with stock 255/60 dunlop tires. I run a 3.42 rear gear with a 4 speed. I have AC and run a stock intake. The engine has a slight chop to the idle and will rip from about 2000 rpm to 5500. I hope to get in the low 13's this next year with current tires and maybe a 12 sec run on drag radial's I think the cam is a great alround choice. I run standard lifters and stock rockers also. There is a little noise from the valve train but its not that loud. I think adjusting the lifters a touch tighter than normal helps. I also got 18 mpg with this combo with the AC on but that was with a lean carb setup. normal is about 13 mpg with richer jets.

[Will]

77ta, get that engine tuned, solve your fuel delivery problems, and you'll be in the 12s no problem.

Funny you should mention the good gas mileage with that cam. I too found it to be really stingy on the gas while cruising just below my torque peak on the freeway (about 3500 RPMs). I think it's because the lobe profiles help the engine run so efficiently that you barely have to crack the throttles to make enough power to cruise on down the freeway.

In my 400 with 3.23 gears and 3000 stall, I could fill up the tank, drive 40-45 minutes to the track on the freeway, make 5 or 6 full passes, then drive home and still have a 1/4 tank or more of gas left.

If you're running a Q-jet you can tune those little primaries to run as lean as possible without surging for best part-throttle economy and throttle-response and setup the secondaries a tad richer to compensate at full-throttle. Since the secondaries handle about 2/3 of full-throttle airflow, the primary jetting has little effect on WOT air/fuel mixture.

Cheers,
-Will

[77TA]

with drag radials I got it to run 13.1 @105.3 last weekend 60ft down to 1.93 from 2.2. I made a pass with a 60ft of 1.93 and missed second gear before getting to the 60ft mark so it would have been quicker than the 13.1 run if id not messed it up. I was getting some wheel hop so I was hesitant to really hammer it right off the line. I was hitting the gas about 10 ft out of the hole on my best run leaving at about 2000 rpm.

[Tomo]

I ran this cam in my 462 with tri-power.
Wasn't that impressed, compared to how the car ran with a tired 400 and the tri-power.
About to install 1.65 rockers to see if that helps. Could be the tri-power.
tom

[Lee]

I've put XE268's in a 455 and a 428. I used "regular" type lifters on both, and neither of them are what I would consider "noisey" at all. Both motors have excellent low-end, and nice power all around.

Lee

[PONTIAC DUDE]

Just watch what lifters you buy, as Crane makes a comparative Rhodes type lifter. Which by the way, in very noisy. All the Cam companies are making this type of lifter and others, low bleed down rate, to help the cam respond with the new stiffer ramp profiles and spring pressures needed to make these cams perform at higher rpms and load. You have to pic and choose a lot more nowadays as there are tons more offerings out there. Later,

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