Performance cam limited to 6000.
If you are gonna limit the RPM, then you might as well chose a cam to make the best of it. And if you do that, then you will have to carefully match the Dcr to it.
A streeter usually runs gears of no more than 3.55s Which will not get to 65 mph in first gear by 6000. That means a shift will be required. If you are running a 904/727 then the shift into second will drop the rpm down to 59% or about 3540rpm. That performance cam, that you want to shift at 6000 will have a power-peak at about 5200. This is a very nice torquey streetcam. It will hit 6000 at about 52mph with 26.5s and 5% TC slip.
Of course, you could get a cam that power-peaks at 6000, but a cam like that will not like 3.55s nor will it like the factory TC. But if you give it what it wants, it will get to the finish line quicker.A 6000rpm power-peak is a mighty big cam. With a 904/727 it will want to be shifted into second at probably over 7000. Your Magnum would need to have an oiling system upgrade to survive that.
Getting back to the 5200 cam; this cam will pull 3.23s easily enough.The new top speed in first will be 55mph. The starter gear will be a little soft at 7.91, so an upgrade to the TC will get you off the line quicker.
Also,of course, you could get any cam in between 5200 and 6000, but IMO, you will just be trading away low rpm power for a few ponies up top.And each cam will require a compression upgrade and or a TC upgrade.And each bigger than 5200 will want to be shifted at a higher rpm, and if you limit them to 6000 then the performance may actually suffer.
What this all boils down to is this; When choosing a cam, try not to get greedy.The numbers on paper are very deceiving. I mean 276 intake duration is only 6 degrees bigger than 270. But these two cams are world's apart in what they require in support works.
And if you don't care about your zero to 55 mph ET, then; I'm sorry to have wasted your time.
But in any case, you kindof need to keep one eye on the Dcr at all times.For a performance street machine, it needs to be as high as possible, yet not so high as to be in detonation all the time.
In a stock Magnum, the pistons are quite far down in the hole, so this should be factored in, cuz if you overcam it, you will end up either pulling the cam out,or band-aiding it with a much bigger TC and probably gears too, or just being sad all the time.
On another note
If the bores are round and without taper, then you are good to go.This is very important. Round and not tapered.
Keep in mind that each bore change of just .001 will change the ring gap by .0031416.So when the piston is going up and down, the rings will be expanding and contracting, and scrubbing in the grooves.
.003 taper will change the gaps by .00942. So your file-fits will be worthless, cuz you kindof have to make sure they have room at the bottom of the bore to not slam shut.Then when the piston comes to the top, the ring-gaps open up and away goes your compression.
So, I know you said the crosshatching is still in there, and I have seen the same on an engine with even more mileage. But I would still run a dial-bore gauge up and down the holes.
