Cam duration

[lefty o]

so what we are saying is, that you have to have the heads/intake/carb to support the increased duration of the cam to actually see an increase in useable rpm.

[Steve.k]

So the heads here and intake are not enough? Im thinking the cam is short. Thats why im asking.

[randy331]

Randy the old motor with single 1050 peaked at 5100 however that was 571ftlb. Now its 595 at that same rpm. Will the car not accelerate faster all things being kept equal?

I didn't say it wouldn't be faster if it made more power.

You asked about cam vs rpm and posted a dyno sheet. I was just pointing out the peak TQ to peak HP rpm spread seemed narrow from the good engines I've seen, maybe a sign of something not matched well.

Randy

[lefty o]

So the heads here and intake are not enough? Im thinking the cam is short. Thats why im asking.

im not saying that, but if you want more rpm and add duration expecting to see an increase in rpm, the heads and intake could be the limiting factor.

[Steve.k]

Like short on duration? What would u change. Car weighs in at 3700. I think the heads and intake are lots ahead of cam.

[randy331]

Randy-----what would you consider an excellent spread ??? Mark H.

1200-1500 rpm is normal on most stuff I've seen.

Our emc engine was 1600-1700 rpm. I've seen 1800 rpm, but being too far apart is probably a sign something isn't matched well, just as much as not enough spread is.

But the application would dictate if a big spread is desirable.

Randy

[swampbuggy]

Thanks for the response Randy, Mark

[Steve.k]

. If you take peak hp which varies by 2hp from 6600-6900 you have 1300 spread roughly. Duration will move peak up for sure. Will we see gains? Thats the big question i guess.

[cjperformance]

I would like to see another .050"+ net lift and 5/8* on the intake.
I dont know the .200" figure on your cam , do you know Steve?
Can you lash the intake tight for a run to try and get a rough idea of what it wants.

[Steve.k]

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Craig thanks. Thats what im wondering? I was hoping to work around lift as clearance tight now. Duration may be tough to get even. But just wondering. Cam card above.

[cjperformance]

Ah bugger!
Are your clearance problems head related- retainer/guide/seal etc at full lift OR piston/valve clearance?
Contact Crane and get the .200" duration or someone here will have it im sure.
I dont see duration alone giving the best result.

[Steve.k]

Piston valve be tight for much more.

[cjperformance]

Piston valve be tight for much more.

Ok, at what lift figure is it tight on intake to piston?

[superpursuit]

.200" duration for crane R-262/420 is 182 degrees.

[cjperformance]

.200" duration for crane R-262/420 is 182 degrees.

Thankyou.