LT1-LT4 Modifications 1993-97 Gen II Small Block V8

How high to spin turboed 383?

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Old 04-20-2012 | 12:03 AM
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Default How high to spin turboed 383?

Forged 9.2 compression 383 with a TC78.

Cam-224/224 .577/.582 114 LSA
Rockers-crower 1.65
Springs-Comp 26094-16. Seat load: 178lbs @1.900''_Open load: 459lbs @1.275_Rate: 449lbs/in
Lifters-LS7 with about .00416" preload

Currently only spinning to 6000, but would like to turn it up a little. I'm making 600hp and 600ft/lbs spinning to 6000.

What should this valvetrain be good to? I've got the 24X conversion so the stock computer is no longer the limiting factor.
Old 04-20-2012 | 12:11 AM
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whens your cam stop making power?
Old 04-20-2012 | 12:21 AM
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I don't know. I was hoping someone with something similar would chime in. Here is the dyno sheet, but I think we had the rev limiter set to low.

Old 04-20-2012 | 12:36 AM
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Originally Posted by LT1 POWR
I don't know. I was hoping someone with something similar would chime in. Here is the dyno sheet, but I think we had the rev limiter set to low.

idk from your dyno it wouldnt do any better to spin it any higher than 6000 it stops at 6200, put a bigger cam in it if you wanna spin higher
Old 04-20-2012 | 12:44 AM
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The graph is deceiving. The motor hit the rev limiter, thats why it dropped off like that and then bounced back up.
Old 04-20-2012 | 12:46 AM
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Originally Posted by LT1 POWR
The graph is deceiving. The motor hit the rev limiter, thats why it dropped off like that and then bounced back up.
its awesome number... I spin mine to 6700 idk why your rev limiter is already adjusted
Old 04-20-2012 | 02:12 AM
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Why spin more rpm? Just turn up the boost for more power
Old 04-20-2012 | 07:53 AM
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You should spin high enough to use the whole top of the power curve. By shifting just after peak power you endup further down the curve after the shift than necessary.

I don't have any boost experience but with an NA setup with a good valvetrain it is typical to turn 4-500rpm past peak
Old 04-20-2012 | 08:38 AM
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powers still going up keep twisting it........if it will go there and not scatter of course......if you plot your shift extention from high to low rpm the line should be straight horizontal on the graph......plot it and thats how high you rev it
Old 04-20-2012 | 10:57 AM
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On your cubic inch with that cam... I'd say true peak power is somewhere between 5800-6000rpm, so like other's said, shift between 6200-6400rpm.

Spinning higher will not make more power though. Only way to do that is to turn up the boost as it sits, or swap out the turbine housing for a bigger one.
Old 04-20-2012 | 01:52 PM
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I run my set up to 6800rpm and the motor still wanted more. But im limited to the stock pcm right now. I would twist it up untill i was no longer making power and adjust the limiter to the results you get.
Old 04-20-2012 | 03:26 PM
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Originally Posted by 96TransAmboosted
I run my set up to 6800rpm and the motor still wanted more. But im limited to the stock pcm right now. I would twist it up untill i was no longer making power and adjust the limiter to the results you get.
That's the plan. Anyone know if/when I'll encounter problems with valve float or anything else.
Old 04-20-2012 | 05:31 PM
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Originally Posted by quik95lt1
......if you plot your shift extention from high to low rpm the line should be straight horizontal on the graph......plot it and thats how high you rev it
Exactly. Very few people seem to understand that.
My power peak is at 6400 and I shift at 7000-7100 because the (relatively) tight converter pulls it down to 5400 on the shifts.
Old 04-20-2012 | 06:47 PM
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On a boosted setup u can makes huge power and still keep the rpms below 6500. Just add more boost. Sooner.
Old 04-20-2012 | 07:00 PM
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with a boosted car they make a lot of power below peak so even if you short shift it. your not likely to lose much et. if you say drop 1k rpm at each shift point you would only drop 50 hp. realistically you will drop less than 750 rpm depending on the trans and convertor.
Old 04-20-2012 | 07:18 PM
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Originally Posted by BIGCAT7274
with a boosted car they make a lot of power below peak so even if you short shift it. your not likely to lose much et. if you say drop 1k rpm at each shift point you would only drop 50 hp. realistically you will drop less than 750 rpm depending on the trans and convertor.
You're also losing the mechanical advantage from gearing which is the bigger factor.
Old 04-20-2012 | 07:38 PM
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Looks like your building max boost at 3500 rpm.

Obviously your cam wants more RPM as its still climbing.
Old 04-20-2012 | 11:08 PM
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The whole point isn't to make more power, that'll come in a couple weeks when I turn the boost up. It's to find the power that's already there. I just want to see what kind of power can be made with only 10psi.
Old 04-20-2012 | 11:18 PM
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What heads do you have?
Old 04-20-2012 | 11:23 PM
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Brodix Track 1. They flow over 330cfm.



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