p4-33

Engine guys,

I need some guidance on putting together some custom ground cams. Bear with me... I'm venturing off into new territory. My goal is something that produces a low and wide tq band, without sacrificing valvetrain durability. I'm also aware that the cam alone won't accomplish this.

First, I've been looking at the Comp Cams Master Lobe Library, both to understand what I have now, ( I currently have Comp custom grinds) as well as make some changes. Is this the "bible"? Do other cam manufacturers have a similar and comprehensive library? Please point me there.

Next, on cam specs: There's differences in the @ .006 duration numbers vs. the @ .050 numbers. Some lobe profiles have narrower @ .006 duration spec with a given @ .050 number, others have wider durations. I assume a narrower base ( @ .006 ) equates to a more aggressive ramp profile, so what's this accomplish? In a marine application, does more aggressive equate to higher torque? Does it move the tq band up or down? And what affect does this agressiveness have on the durability of valvetrain components?

Comp Cams generally has 4 lobe profiles that appear geared toward marine hydraulic applications; High Energy, Magnum, Dual Energy, and Xtreme Energy. Comparisons of @ .006 specs vs. @ .050 specs show the aggressiveness of these profiles from low to high, relative to the above list. Can someone characterize how these profiles relate to marine use? Tq vs hp? Wider or narrower tq curve?

Also, does anyone have any experience with the Comp Xtreme Energy profile lobes? These have an inverted radius ramp design. What's this for, and what's your experience relative to valvetrain durability? They supposedly make pretty decent torque.

I realize these are very vague questions, but I have to start somewhere. I have a LOT more questions, so again, bear with me. I've heard good and bad here on Comp Cams... who else does custom grinds?

Thanks in advance,
Brian

TC

Call Comp and ask for Gordon Hollowell. Gordon can answer all of your questions about their products and help steer you in the right direction. Gordon works with many of the Nascar teams as well as the drag racing circuit. There are numerous cam specialists on this board and I'm sure this will be hot thread. Good luck!!

Nordicflame

Don't forget to look at the Extreme Energy XFI HR grinds as well. (they're not just for EFI setups) These have even slightly more agressive ramps as well. These more aggressive ramps also appear to reuce overlap a bit compared to a gentler ramp which should help with reversion when comparing similar @ .050 numbers.

After some lengthy conversations with Comp I just ordered and received in 5 days a 238 Extreme Marine High lift grind int / 248 XFI grind exh and had it put on 114 LSA for a 565ci motor with GM heads.
(Adv 294/300) 238/248 114 .612/.615

You should get a lot of good input here.
Oh yea...It was $249 for any grind you want from Summit

Dave

cstraub

Without knowing what the cam has to work with (airflow) all you can do is guess at a profile.

Along with airflow the combination and the rpm range is then considered. Lobe selection looking at duration on the seat, .050", .100", .200, .300 and so on can be catered to the engines requirements.

If this is a competition OEM headed BBC then you may want to look at grinding cams with 2 intake lobes, 1 for the good runner and 1 for the bad runner. This is old Pro Stock stuff but works very well on class limited engines. These cams are expensive but will squeeze more power out of the engine.

Nordicflame

I was assuming he knows that data and is trying to find a grind to fit his particular needs. There are many, many grinds available thru Bullet, Cammotion, Comp, Crane etc... that would more than likely fit his flow profile at a decent price.

Might as well swap 4 and 7 lobes while your at it Comp does this for a minimal charge.
Unfortunately I found this out after I ordered

cstraub

Dave,
I wasn't knocking your advice, just giving mine to Brian. Comp is a great company but your correct there are a ton of great cam companies out there:

Demos
Reed
Cam Techniques
Cam Motion
Schnieder
Elgin
Cam Craft
Bullet
Lazer
Airrington
Hyder
LSM
Jones
Cornett
Huggins

Sometimes the smaller guys can spend more time with you.

Steve A.K.A RAMPAGE

I would also try to get ahold of RMbuilder (Bob). He's an excellent source to speak with when it comes to custom ground cams for marine applcations. N.Y. (585) 654-8583

BenPerfected

Hi Brian,
Consider talking to Dave Generous at Cam Techniques. Dave throughly understands the marine needs...all of them. Last winter, we Spinton tested my valve train to 7000 RPM. The valve train stability was absolutely excellent, very smooth. The only change we made while on the Spintron was to increase the exhaust push rod wall from .125 to .160 (increased weight and stiffness).
These engines, including Dave's cam design, exceed all expectations on the Spintron, the dyno and in the boat.
As you know, I run my boat hard and I spend significant time above 6000 RPM. This package is excellent at top end, acceleration and idle.
I never checked my valve lash last year. As the engines sit on the shop floor, neither the intake or exhaust lash changed .001 in 2005.

Elite Marine

Contact Bob Madera at Marine Kinetics. He set me up!!

RMBuilder on the board.

Hot Boat

Jason Saris at performance marine in lake George has experience with custom grids and also request specific billets that the cams are forged from. I got mine from him. The cam was made by Iskidarian (sp?) The motor builds lots of tork.