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Author Topic:   RPM on a 383
udecide66
Member
posted May 26, 2004 04:14 PM
If you are lugging the engine at that speed you may be harder on it than gearing it to run higher rpms. That combination will prob pull to 7000 or better. But if you only want to turn 6000 then go to a little smaller cam so that you make more torque at your target rpm that will make it perform better. The weakest link is your crank. A forged crank and 6" rods would be better insurance. I would prob look to turn more like 6500 minimum and really 7000 would prob work better as long as you dont tear up the crank.


sixwillwin
Member
posted May 26, 2004 06:36 PM
I ran nearly the same motor as you described, I turn it 6800-7000 every nite. Works well.....

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tilley88
Member
posted May 27, 2004 02:01 AM
Nuthin wrong with a Scat crank. Best Chinese junk you can get. It's still American steel. Twist 'em hard, 6600-7000 rrrr's. Anything more is probably beyond your tork curve.


21racer
Member
posted May 27, 2004 06:23 AM
your torque range will be about 5500 hp will be around 6500 you can turn it on up to 7000. had one and loved it. had cast crank from speedway motors,stock rods and speedpro piston ran 25 nights then crank broke cheep crank!!!!


Racer0
Member
posted May 27, 2004 06:38 AM
Why not throw it on the dyno and run it - a couple of pulls and you'll know where it makes power and if the cam is too big for that combo - best $75-100 you'll ever spend to find exactly where that combo will run - plus you can do some tuning to find more power (jetting, timing, etc.) - have seen 20-25hp gains on the dyno all the time from engines that were already "set up" to run...

Best RPM range for power of that engine will be dependant on head flow, intake flow, carb, exhaust flow, and of course CAM design / specs. Everyone on here is just guessing at the RPM range where it makes power based upon a combo that they put together or had put together for them... there wasn't enough info to accurately guess the combo's power/rpm range. Heck we don't even know if you're running stock iron exhaust manifolds and 2" pipes/mufflers like some classes require... that would cut the exhaust flow down a lot over open headers..

Raz_900
Member
posted May 27, 2004 01:05 PM
I would be more concerned about the bearings and/or block spinning over 6000. If it's a stock 2 bolt with stock main bolts and stock replacement bearings, it's gonna live about 15 laps above 6500.

If it has ARP studs and HP bearings, I'd advance the cam 4 degrees and gear for 6700 max. It'll make virtually the same power as spinning over 7000 but will live a longer life. And as stated above, the rest of the combo makes a big difference in RPM. A 2 bbl carb and stock manifolds limits you to around 5500-5800 on a 383 max. More than that and you're doing nothing but wasting gas.

Picture stuffing an elephant through a coffee stirrer. That's what a 383 would be like through a 2bbl and into stock manifolds and 2 - 2 1/2" pipes at 7000 rpm.

udecide66
Member
posted May 27, 2004 01:32 PM
i turn my 383 7300 with a large 2bbl (890) and it pulls hard all the way to the end of the straight. it could go more if i wanted it to, but i think my valve springs wont handle much over what i'm giving them now. with a 4bbl and headers it would be well worth it to turn it 7000+ rpm.

luke

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JMillerJr76
Member
posted May 27, 2004 05:48 PM
I built a motor for my cousins modified, with the 215cc 49cc chamber dart heads, flat tops 6. inch rods and a 9000 series scat crank, and he told me that it pulls all the way to the 7800 chip he felt that it still had more! I would rather zing a motor than lug one, the only engine failures we have had was from lugging the motors, the next race night after lugging one, we would break the cranks.


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