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Discussion Starter · #1 ·
As long as I have the head off I want to put in a performance cam. It's a '72 and it's pretty much stock except 6/2 headers w/resonators. I want to boost power in the mid rpm range (3-6k) but I don't want to have to set the idle too high (under 1000 would be nice). I'm looking at two cams from Motorsport. One is 274/274 with .480 lift. The other is 270/280 with .460 lift. Has anyone had experience with these or similar cams. Or any other suggestions?
Thanks, SoM
 

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I just installed 274 cam in my car. it's good in the power range you're talking about. 270/280 cam, you need to raise the compression to 10 to 1 or so to be effective. later
 

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Re: MORE...What cam to choose?

What about for a mild build of a L26: 1mm overbore, 6-2-1 tube header / exhaust, SM Carb needles, Adjustable (NISMO) cam gear...I was thinking about the 270/280/.460 cam also -or- the NISMO L7 cam 270/270/.475
 

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Both camshafts have too much duration for your application. A better choice would be the 260 degree camshaft from Comp Cams. It will increase the torque output from 1600 to 5500 RPM and actually make the car easier to drive than the stock camshaft.
 

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Discussion Starter · #5 ·
jerja,

A couple questions...

What is the issue with too much duration? Is it dropping the manifold vacuum?

What is the lift on the 260 from Comp Cams? (There's a 260 from Motorsport that's .460)

Also I should have told you, this is part of a progressive upgrade. Can I live with a higher performance cam until I upgrade the compression?

Thanks for your input, SoM
 

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Re: jerja,

The 260 grind has .420 lift and works fine with good stock valve springs.The long duration grinds reduce the mid and low RPM torque. This is very evident unless the compressio ratio is increased. Unless some good head work is performed (porting, valve unshrouding, port matching and compression increase) a shaft with more than 265 degrees duration will almost always hurt performance.

It would be worthwhile to live with it only if you plan on an upgraded head that is capable of flowing more air. Performance part selection should always be built around the cylinder head flow, compression and intended use.
 

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Comp Cams has their catalog screwed up. They list the L-6 cams as L-4. If you purchase the 260 shaft the proper P/N is 84-123-4. You can get it from Summit for around $110.00.

My setup is:
Stock displacement 1971 240
Ported E31 head with stock valves and port matched
10.5 Compression
Headers with 2.5 pipes
Stock SU's
Comp Cams 260 camshaft
Pertronix module and coil
Stock valve springs

Engine dyno results at the rear wheels corrected:
145 HP @ 5300 RPM
137 Lbs torque @ 2400 RPM
145 Lbs torque @ 4800 RPM

As you can see the torque curve is really flat. The engine idles smooth at 800 RPM with 16 inches of vacuum. It will blow the doors off a stocker shifting at 4500.

The single biggest mistake that most poeole make is installing a camshaft with too much duration for the cylinder head flow. If in doubt always select the camshaft with the shorter duration.
 

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Discussion Starter · #8 ·
Thanks for the help...

I'll check back to see if anyone else posts, but I guess I have to think about how much $ I want to sink into the head while it's off...
SoM
 
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