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Old 03-13-2008, 12:53 PM
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Racing Motor - Cam selection

So here's another thread about selection for my camshaft. I am building a 283 for circletrack motor and am meant to be leaving the enginge stock as equipt from factory! Now obviously nobody does that unless you're really green The rule that I have to keep with is the 15" of vacume at 800 RPM. Other than that someone will have to do a tear down of the motor and then check grind numbers to check the camshaft.

Here are the two that I am looking at and then I have a few questions.

Comp Dual Energy 12-208-2 Summit Racing Link

Comp XTREME Energy 12-238-2 Summit Racing Link

I am already planning to use Rhoads lifters to help on the idle quality and vacume readings. Here are my questions:

What is your recomendation among those two camshafts? I have to run stock manifolds exaust (center dumps) and intake. I have unmodified 60cc chamberd GM heads and my 283 is not bored. Do you think the vacume will be alright?

The notes on both the camshafts say [2] Requires machining on cylinder heads. *** does that mean? could they be a little more ambiguious? What will need to be machined?


Last edited by Bull_81073; 03-13-2008 at 06:28 PM. Reason: correction
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Old 03-13-2008, 11:07 PM
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No ideas? I usually get a near immediate response! I was hoping for some feedback since I need to start buying my parts!
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Old 03-15-2008, 05:51 PM
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To be competative, a 283 will need to buzz a lot higher than a 350.
Use a short/moderate duration solid lifter cam in your C/T 283. LSA should be 110++ for good manifold vacuum. You need to get busy on those cylinder heads if you expect to run with the pack. (compression ratio and flow)
I would suggest one of the milder Comp Extreme tight lash, solid lifter grinds, possibly, but not necessairly custom ground on 112-114LSA for max manifold vacuum at idle.

Hyd's are for sissys.
Consider one of these comp cams you can look up the specs yourself
comp #12-222-4 12-223-4 12-674-4 12-675-4 12-676-4 12-677-4
the larger ones may need to be ground on wider LSA to meet the vacuum limitiation. Maximize the spark timing at idle to maximize the idle manifold vacuum. Up to and including locking out the timing curve. Compression ratio is your friend.
Don't be afraid to play with the installed cam phasing (adv/retard) to adjust the usable power band to dial in your 283, especially on the milder cams in the series. Just be aware that later intake valve closing point timing needs compression ratio. Don't be shy on the rear gear ratio.

Last edited by F-BIRD'88; 03-15-2008 at 05:58 PM.
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