RPM stock crank built bottom end.
- Thread starter CD07GT500
- Start date
With a billet crank gear and oil pump gears and rods, 7000k at least.
BUT the key to your redline is your valve springs. Stock 07-12 id stick to 6500 unless your valve springs are also upgraded.
BUT the key to your redline is your valve springs. Stock 07-12 id stick to 6500 unless your valve springs are also upgraded.
Even with upgraded valve springs, if your cam isn't making power up to 7,000 rpm, you're just beating up the valvetrain taking it north of the power peak. I probably could take mine to 7,500 rpm without remorse, but my max power number is likely in the 6,600 to 6,800 rpm range, so I have no reason to go there. Rev limit set at 7,000 rpm. Ported VMP Gen II with 10% lower, 2.5" upper. Rods are Manley I-beams.
What blower and pulley combo?
The blower and pulley combo will usually dictate peak power more so than the cams will. I am only asking from a crank perspective not valve train. Of course less rpm is better on valve train components. Shifting at peak is usually not optimum.
So 2.5 upper stock lower?
Boost may determine peak power, but the rpm it occurs is based primarily on the camshaft. Case in point, here is BJ's dyno numbers from an article in Ford Muscle with his new, built bottom end sporting 9.7:1 compression ratio with the difference between the two sets of numbers being camshafts only. BJ is not making any more power beyond 6,250 with his stock camshaft despite the fact that he's running 23 psi of boost. This is with a Gen II R, with a 15% lower and 2.4 upper. Boost is down 5 psi with the NSR cams. That's the same rpm power peak you'll see for a bone stock 5.4. There's no shortage of dyno charts in the sticky section of this forum that show the same thing from engines in between. I think the peak on the NSR cam is with his stock valve springs with 50k miles on them.
2.875 upper 10% lower
So he made peak power within 500 rpms going from cams way too small to cams too large for the combo. He could put 3.4 whipple with a 4"/7.1" pulley on it and make peak power close to 8000. Then run a 2.5"/8.12" combo and make peak power @ ~6600 all with the same long block. The blower/pulley combo will dictate peak power more so than cams will.
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Do what with stock valve springs? That cam has more in it with more lift but the cams are still to large for the combo. Regardless the valve train is not in question a stock CJ crank is. This thread was to gather a consensus on stock crank combos. Again springs aside blower/pulley combo will determine the peak more so than cams regardless of what springs BJ used.
Not hard to understand. Just pointing out that BJ did not have valve float. Same cams with a Sullivan manifold will make peak power much higher. Hence why I said the blower determines peak power more so than cams.
I think he means that the valves will float if you spin it too high. Sure the cam probably has the capability but the valve train does not.
If that is the case he is off base then. My car with stock cams same pulley combo as BJ made peak power around ~6400 just as his did. With large cams he made peak around ~6800. With stock lower 2.4 upper my car made peak at ~6800 with the stock cams.
13/14 use the same valve springs.
With a billet center counterweighted crank, rods, OP gears and springs these engines will go 8k+ without issue.
With a stock crank I wouldn't go over 7500, Mihovetz says 7200 is reliable limit. Stock/Cobra Jets flex and beat out the #3 main if you take a stock crank too high, too often.
This, especially on blower cars. A better balancer may give you some better life out of it as well.
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