Need help picking a cam.....

[jschiller]

I am in the pre-build stage of my motor and need help sorting out all the cam options out there. The engine is a .030 over 428 CJ, forged pistons 10.0 CR, either a Blue Thunder 4x2 with 2 Holley 450's or Edelbrock Performer RPM with a 750 Holley, iron CJ heads, WR Toploader and a 3.31 rear.

I am looking for moderate HP out of it, 425-450 max is fine. This is a street only car.

I can't decide if I should go with a hyd roller or flat tappet cam, but leaning toward the mech cam. The roller should be maintenance free but there's something about the clickety-click of the mechanical cam that says Cobra to me.

All suggestions welcome. Give me the benefit of your experience and save me !! I'm going nuts here.

John

[Excaliber]

First of all you should be looking for a 'Cam Kit'. Comes with lifters AND valve springs to match the cam profile. Push rods MAY have to be custom if your engine block has been cut down, the heads are shaved or your rocker stands are 'non standard' in height (to tall or to short for the block\heads combination).

I went with a Comp Cams 292S flat tappet. Pulls nicley from about 1800-2000 to 6200 or so. Nice street cam with a mild 'lumpy idle'. You NEED a 'lumpy idle' for the proper sound in a Cobra.

This cam (as do most) requires inner valve springs which MUST be removed for the critical 20 to 30 minute breakin period. The inner springs are reinstalled after break in. The nice thing about a roller cam is no break in to speak off, minor at least. BUT, NO WAY I would run a roller solid for a street application, there for race only, as they WILL fail on the street. Certain EXPENSIVE options exist to make a roller 'live' under street duty. A hydraulic roller is a great option for the street, BIG dollars compared to flat tappet. Not to mention I don't care for a hydro cam anyway.

See my engine build thread for more information on breakin of a flat tappet cam.

Ernie

[decooney]

In your CJ a regular solid or hydraulic flat tappet cam will do just fine for what you are looking to accomplish; you can spend the extra money on a nice FE rocker arm assembly or something. Good Luck.

[jschiller]

Ernie and Duane--

Thanks for the feedback.

Is it accurate to say that a cam for a 428 would be suitable for a 427 and vice versa if the other components stay the same? In other words the longer stroke in a 428, bigger bore in a 427 have no large impact on cam choice?

John

[Excaliber]

I'm running a 428 crank in mine, the stroke isn't 'that important'. What is of more concern is matching the cam with your expected cruise rpm (read that rear gear ratio) and heads, intake, exhaust system etc. Cam selection is one of the more tricky things to get right.

Lets say your running a 5 speed (poor misguided soul that you might be ) and your cruise rpm for your typical mph on highway is 2200 rpm. Yet your CAM profile prefers 2500 or higher rpm. You got a problem! The motor will not be happy being below the cam curve. You will find yourself speeding up or downshifting into 4th (which is what you should have anyway ).

[decooney]

John,
What Ernie is telling you is so true. If you undercam it, cruising on the freeway with a WR 4-speed and 3.31diff ratio is noticeable like the engine is straining to rev. If you overcam it, and say the power is in the upper 3k range, it will feel like you need lower rear diff gears to keep it in its sweet spot. Many people have done the WR Toploader with 3.31s and its sort of an agreed standard when running the 428s especially.

I bascially have the same heads/trans/diff ratio as you. I've tried the 282s, 300s, a 295s-custom grind I have now, and friends with the 270h and new 286h cams. If you want to do a solid cam and not so radical, the 282s is a nice all around cam. I had this in my last car and it was great. If you want to go with a bit more rumpity rump and higher rpm performance some people like the 294s cam like Ernie was talking about. I did a custom grind just a tad more lift/dur than the 294s. I prefer it because I wanted it tad more radical. I don't know, if I had to do it over again, I'd probably drop back down to something like the 286H, but in a solid cam; custom made. I think Comp came out with this one so it would be right between the other two, but I don't think they make it in a solid grind yet. You could copy it and do a custom grind cam like I did from Crower. In my case I took two cams and compared with software on three different 3 mile track scenarios for reference and split the difference on a few parameters. So far so good. Like he said, matching it all up is the trick and including spot-on carb tuning. Once you get it dialed right in, it makes it that much more fun to drive in varying conditions.

To me, cam selection and drivetrain setup really comes down to how you plan to drive the car 80% or more of the time.

[Loadco]

You can't go wrong with the 282S. Great street cam. Nice sounding idle and good power down on the low end which is important for street driving (especially with 3:31 gears). That's what I'm running in my 427.

[trularin]

May I suggest you contact Keith Craft. There are tried CAMs that they know about that will work for your application.

Just a suggestion.