Estimating power? 421 Stroker.
12-31-2007, 01:35 AM
#1
Estimating power? 421 Stroker. Is there possibly any theads I can research this aspect? Im getting close to purchasing parts for my build Im really focused on the round about numbers the engine could make..
421 w/ large cam(undesided) and High flow heads (undesided) 11:1 Compression
Looking for some guidence/motivation to get me on the project
421 w/ large cam(undesided) and High flow heads (undesided) 11:1 Compression
Looking for some guidence/motivation to get me on the project
12-31-2007, 06:34 AM
#4
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My 421 makes 560rwhp@6200rpm with LS6 heads and a solid cam. The FAST intake is really holding it back, if I were you I'd use a single plane and you shouldn't have a problem making close to 600 with a big cam.
12-31-2007, 08:05 AM
#5
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Brake Mean Effective Pressure (BMEP) or torque per cubic inch @ power peak rpm is a good method for predicting horsepower, as it doesn't vary much from engine to engine. If you want to predict peak horsepower, an above-average, reasonably price build might have around 170 psi BMEP at the flywheel or about 1.13 lb-ft per cubic inch. For a 421 that's 475 lb-ft at power peak rpm.
If you get max power @ 6500, that 475 lb-ft is just shy of 590 fwhp or perhaps 515-520 at the tires. If KC's 421 makes 560 rwhp @ 6200, he is achieving about 475 lb ft at the wheels or perhaps 540 lb ft (637 hp) at the flywheel. That's 1.28 lb-ft per cube or 193 psi which is quite good.
It's more difficult to get BMEP as revs increase, but the best Sprint (Nextel) Cup open engines make about 213 psi or 1.42 lb-ft per cube @ about 8800. If a 421 LS street engine made 1.42 lb-ft per cube at 7000 it would have about 800 hp at the flywheel and maybe 700 at the tires. That would certainly be a challenge. LS6 heads have done 1.42 lb-ft per cube on 300 cubic inch engines, but not on 421s.
600 hp at the wheels at say a reasonable 6800 rpm is 1.25 lb-ft per cube or nearly 190 psi BMEP. I think this is doable, but it won't be cheap. It also won't be an "internet-designed-by-commitee" engine.
FWIW, the highest NA engine BMEP is probably a Pro Stock 500 cube mill @ 1.60-1.63 lb-ft per cube (@9500+). If you could do that on a 421 @ 7500 you'd have over 960 hp @ the flywheel and about 850 at the wheels. That would be impressive....and very costly.
Jon
If you get max power @ 6500, that 475 lb-ft is just shy of 590 fwhp or perhaps 515-520 at the tires. If KC's 421 makes 560 rwhp @ 6200, he is achieving about 475 lb ft at the wheels or perhaps 540 lb ft (637 hp) at the flywheel. That's 1.28 lb-ft per cube or 193 psi which is quite good.
It's more difficult to get BMEP as revs increase, but the best Sprint (Nextel) Cup open engines make about 213 psi or 1.42 lb-ft per cube @ about 8800. If a 421 LS street engine made 1.42 lb-ft per cube at 7000 it would have about 800 hp at the flywheel and maybe 700 at the tires. That would certainly be a challenge. LS6 heads have done 1.42 lb-ft per cube on 300 cubic inch engines, but not on 421s.
600 hp at the wheels at say a reasonable 6800 rpm is 1.25 lb-ft per cube or nearly 190 psi BMEP. I think this is doable, but it won't be cheap. It also won't be an "internet-designed-by-commitee" engine.
FWIW, the highest NA engine BMEP is probably a Pro Stock 500 cube mill @ 1.60-1.63 lb-ft per cube (@9500+). If you could do that on a 421 @ 7500 you'd have over 960 hp @ the flywheel and about 850 at the wheels. That would be impressive....and very costly.
Jon
