273 commando Build
another thing isky told me was this t3 cam was good from 2000 to 6400 peak power. the engine seemed really happy around 5800 and was still climbing .. I never took it above 5800.
from what you are telling me this t3 cam was all done pulling under 4800 is not even close . I can assure you of that lol
When I mention a powerpeak, that is exactly what it says , the rpm at which the power on a dynograph has reached it's highest number.
This has nothing to with the engine's redline
nor to it's shift point.
It's just a powerpeak.
The peak can be long/relatively flat, or it can be short/narrow/ and pronounced.
In a given longblock, in most instances this includes with headers, this peak cannot be moved around much. Yes you can increase/decrease the horsepower number, a little bit, at the peak, with intake carbs spacers and so on, but fundamentally, the rpm of the peak doesn't change much. That will take a different cam, or at least a different LSA..
Your shift point, for a fast trap speed is related to the powerband requirement of the transmission. With a 4 speed this is easy cuz each gear is nearly the same shift split of about 72%. So then whatever rpm you shift at, in the next gear, the rpm will drop to about 72%. and you want the incoming power to be at or near the same as the outgoing power. With a 4-speed, this is gonna be about 400rpm past the peak power, depending on a host of engine parameters. So if your power peaks at 5000, then you might outshift at 5400, and you're looking for the same incoming power at 5400x .72=3900; thus your powerband is from 3900 to 5400. From there you gotta go out and test it. But thru the traps you wanna be very close to, if a lil past, peak power.
If you shift too early, your rpm will fall further down the powercurve, making your engine struggle to get back up on the cam.
If you shift late, you should come in at a higher power, but leave at a lower power. I like this a lil better, cuz this gives the car a lil kick-in-the-azz; but your engine has to survive the extra top-end rpm.
Now, if you have an automatic, that's a whole nuther thing.
So
If your engine is pulling past 5100, with a 222/108 cam, that only means one of maybe three things;
1) the cam you installed does not match the camcard you posted, or
2) the cam has flat-lined early, due to environmental complications, or
3) you haven't actually driven it fast enough to feel it nose-over, cuz until you do, there is not enough time to actually feel it.
The camcard you posted says 44* of overlap. With headers, that should put a nice lil power bulge on the power curve. With headers but a less than stellar exhaust system, or without headers at all; that would mean a long flat power curve/without a powerbulge, like a 340... So yeah, I get it, that you might think it's still pulling at 5800.
I assure you, that I have had bigger cams in much more potent SBM engines than your 273. I even had a cam similar to the one that you posted the camcard for, and while it was a nice hi-torque cam(223/230/110/51overlap), it peaked at around 5000.
Oh sure that lil cam pulled to 7200 as well, but it was way past pulling hard. I just went there cuz she sounded awesome, screaming thru dual 3" cannons, and she was happy about it. The thing is, until it hit mid-Third gear, there was no way to feel the nose-over, cuz at WOT, the tires were still spinning.
I'm glad you like your 222/222/108 cam but 050-wise, let's face it; it's just not that big.
Get yourself a windshield-mounted accelerometer and it will reveal the truth to you.