Reply to "Questions regarding George's 275/285 Custom Street Cam Profile"

Safe rpm limit will be determined by the valve spring pressure vs. the total mass of the valve train.


I think that stock you are looking at a single spring and dampener at something like 285 #'s open. Maybe 35#'s on the seat? Right there with those valves the safe rpm limit is probably just a little over where the cam runs out of enthusiasm? About 6,000 rpm.


The rpm potential of the camshaft, by the timing events mostly. A little by the valve lift? But the valve lift is more to match the flow of the valves.

The iron 4v heads with a good valve job on the intakes flow around 300cfm at .600" lift. Less lift, less flow. So you match the lift to the flow of the ports.


The fact that it has roller lifters has almost nothing to do with the cams performance. That would effect total gas mileage more than anything else from less internal friction (maybe 1 mpg better?) and lower your need for ZDDP in the oil. Thats all that they do here.


It strikes me that the timing events on this proposed cam are very similar to the stock CJ cam, just with roller lifters.

The characteristics then should be very similar to a stock CJ cam, i.e., all done by about 6000rpm.

It doesn't have enough duration or overlap to continue past that. Centerlines are wrong for high perfomance. Those need to be 110.

If you want to go faster, more rpm with power, then you need more duration, tighter centerlines, and more overlap.

On a 2 valve engine, that's the only way you can do it.

That means you need to put up with a more radical idle, more valve train noise, more exhaust noise.

If not, then you have to go to a 4v, dual cam engine and have the primary cam idle like a pussy cat, and the secondary cam goes ape?