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Old 10-06-2005, 09:43 AM
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Help With A Cam

I'm looking into getting a new cam for my new Chevy 350. Right now I've decided on a Competition Cams product.

My last 350 had 12:1 compression and was using a Reed mechanical cam with 264-268 duration and with a .555 lift, it ran 11.8 in the quarter

My new engine will have 10.5 compression with aluminum heads and the cam I'm looking at has these specs:

CCA-CL12-225-4

Brand: Competition Cams
Product Line: Competition Cams Magnum Solid Cam and Lifter Kits
Cam Style: Mechanical flat tappet
Basic Operating RPM Range: 3,000-7,000 RPM
Intake Duration 050 inch Lift: 260
Exhaust Duration 050 inch Lift: 260
Duration at 050 inch Lift: 260 int./260 exh.
Advertised Intake Duration: 306
Advertised Exhaust Duration: 306
Advertised Duration: 306 int./306 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.555
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.555
Valve Lift with Factory Rocker Arm Ratio: 0.555 int./0.555 exh. lift
Lobe Separation (degrees): 110
Intake Valve Lash (in): 0.022
Exhaust Valve Lash (in): 0.022
Grind Number: CS 306S-10
Computer Controlled: No
Lifters Included: Yes
Lifter Style: Mechanical flat tappet
Valve Springs Included: No
Retainers Included: No
Locks Included: No
Valve Stem Seals Included: No
Timing Chain and Gears Included: No
Assembly Lubricant Included: Yes
Pushrods Included: No
Rocker Arms Included: No
Gaskets Included: No
Quantity: Sold as a kit.




What do the techs here have to say about it?

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Old 10-06-2005, 09:52 AM
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Too long for 10.5. Try something in the 235 To 240 range.
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Old 10-06-2005, 09:56 AM
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Too much duration
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Old 10-06-2005, 01:10 PM
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What would you all recommend?

What would happen if I used this cam?
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Old 10-06-2005, 01:21 PM
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cam

duration should be in the 235/245 @.050 for this engine if it is a tru 10.5:1... If it going in a heavy car 3200lbs plus i would stay on the lower end, if it's in a lighter car with good exhaust, converter, intake go to the larger number...



Keith
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Old 10-06-2005, 01:27 PM
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Charlie, I'm not a professional engine guy, but this just seems extreme. Do you ever plan to drive this beast on the street?? If so, I'd back down.

Also, with this much duration, and aluminum heads, I'd imagine that on 92 Octane you could pump up the compression a bit higher . . . . but that wasn't the question and I'm not paying the bills for detonation if I'm wrong.

If you're ever gonna drive this thing on the street, I'd agree with one of the prior posts, something under 245 @ 50 makes a lot more sense.

I notice this is a single pattern cam . . . . .Are you using AFR heads??

Pat
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Old 10-06-2005, 03:13 PM
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What are the heads on this thing?
What is your max rpm?
What rod length is this thing?

If you are going to turn this girl to 7200 rpm I don't have a problem with the duration numbers, I have a problem with the lobe sep and the lift. It will need to be tighten a little and you will need some large ration rockers.

Now if this is street driven weekend warrior then yes you need to back way up.

Chris
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Old 10-08-2005, 10:13 PM
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Assuming you're using the same intake manifold, open headers etc
and are going drag racing with it, something like this should work well.

Comp cams #12-502-5 Look up the specs online at comp cams.

This is a tight lash cam with intense lobes. the short 280-284 running duration will match your 10.5:1 compression ratio better. This cam should be degreed in and advanced in the motor about 4-6deg from straight up. Intake lobe C/L @ 100-102. It's ground on 106LSA.

If you just got to have a huge cam try Isky cams #201549 Look it up online.
it is also a intense tight lash cam.
This cam also should be degreed in and advanced to 99*-102* intake lobe C/L
Both these cams work well on 10.5:1 motors.
They are plenty big to make good power. If you drive on the street I'd use the Smaller comp cam thou.
How will you be using this motor? what other parts are you using on it?
rear gearing? torque converter stall rpm?
Both these cams are stocked by Summit Racing.

Last edited by F-BIRD'88; 10-08-2005 at 10:19 PM.
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Old 10-08-2005, 10:18 PM
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Mysterious 396 SS

I've heard that if you have a lobe center less than 114 degrees, you will have vacuum problems with accessories like Power brakes etc
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Old 10-08-2005, 10:33 PM
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Quote:
Originally Posted by bgp
I've heard that if you have a lobe center less than 114 degrees, you will have vacuum problems with accessories like Power brakes etc
You heard wrong. Or at least didn't get the whole story. If the cams duration is long enough, the manifold vacuum will be low enough at idle, the the Power brakes don't work reliable all the time.
A cam ground on 114Lobe centers has less overlap than a cam with the same duration but ground on tighter lobe centers like 108 or 106.
Wether the brakes will be affected depends on the duration and then to a lesser extent the lobe separation angle.

Both the above cams will work ok with power brakes on most cars.
Both these cams require significant increased initial timing at idle and idle rough at 800rpm. The larger one will want the mechanical ignition timing curve in the distributor locked out with full advance at idle for best results.
If you still have trouble with the power brakes you can add a vacuum resiovor canister, (comp cams) inline between the power brakes and vacuum source. You can also add a electric auxillary vacuum pump. 1980's era GM mid sized front wheel drive cars and some Caddilac's have them.
I have used cams this big on cars with power brakes before. they worked ok.
Once the motor is set up right.
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