SBC TPI 383 ways to reduce torque

[sanderson231]

I do not agree at all. No other intake except the belt driven kind will make more mid-range torque. NONE of them!

I do not agree at all. No other intake except the belt driven kind will make more mid-range torque. NONE of them!

I watched a couple of the Richard Holdener videos and it is crazy how much peak torque the TPI intake makes. But the problem is that the OP is concerned about too much torque. So that leaves three options; 1) detune the engine to make less torque (and give up HP), 2) drive the car conservatively or 3) use a different intake. I like sports cars that feel like sports cars (Quad 4 in a Pontiac Fiero) so I would select the latter.

There is a lot of reasonable experience in the Fiero World running V-8's and 3800 supercharged engines on a 5 speed, manual transaxle rated for 200 ft-lb. So I think that GM's torque ratings are conservative. I suspect that the 383 the OP has chosen with a TPI intake would be reliable with no other torque management than reasonable use of the right foot.

[nilak]

I watched a couple of the Richard Holdener videos and it is crazy how much peak torque the TPI intake makes. But the problem is that the OP is concerned about too much torque. So that leaves three options; 1) detune the engine to make less torque (and give up HP), 2) drive the car conservatively or 3) use a different intake. I like sports cars that feel like sports cars (Quad 4 in a Pontiac Fiero) so I would select the latter.

There is a lot of reasonable experience in the Fiero World running V-8's and 3800 supercharged engines on a 5 speed, manual transaxle rated for 200 ft-lb. So I think that GM's torque ratings are conservative. I suspect that the 383 the OP has chosen with a TPI intake would be reliable with no other torque management than reasonable use of the right foot.

The car is registered as historical, I have no idea what kind of checking they will do for the next inspections so it’s safer to stick with the stock intake.
I can apply appropriate throttle and that will be more efficient and safer for the engine but I don’t know how consistent can I be. The engine can produce high torque even at a small opening of the flap, but It should be that hard

[steveo]

the logic still seems weird to me. you could choose any engine in the world, you went and chose one that you feel is way too powerful, and you want to repair that error electronically to make exactly the powerband you want.

it's possible to get close by making your ignition and AFR totally incorrect (a purposefully bad tune) but considering there is a gigantic lobe filled rod that contains most of the actual parameters controlling your powerband, if you really want to reduce low end torque and increase high end power, and the bore and stroke must remain the same, the correct parameter to modify is the cam

are you sure you can't just spend the extra time and money beefing a few things up to handle the power?

[sanderson231]

I just looked up specs on 1991 ZF6 transmission and it is rated for 450 ft-lbs. Not sure what the clutch and rear end is good for but doubt that the transmission is too weak unless you like to rev to 3000 rpm and drop the clutch.

[nilak]

I’ve watched this presentation youtu.be/E0yZdLkpvR0 some while ago and these guys did some extensive research on this transmission. They say it can handle even 475lbft although it’s rated by the manufacturer dor a lower torque (I think 400lbft). But taking into account it’s now over 30 years old and 130k miles, I thought something like 400lbft would be better for reliability. Anyway 12% over 400lbft does seem a huge step, it could be safe.
Another problem can be the the C beam, but that basically depends on the output torque not input (engine) torque and I think can be a problem if you use drag tires even with std engine, 1&2 gears can generate enough torque up to race tires traction break up.

[LeMarky Dissod]

nilak, IFF I were stuck in your shoes (big if), I'd start by:
a. calibrating the spark map using 87 octane instead of 91 or 93
b. NOT using WOT-PE below, say, 2750RpM
c. under-utilizing WOT-PE from 2875-4000RpM
d. saving for a smaller cam, if not a smaller crank or engine (whichever happens to turn out cheapest)

[sanderson231]

IÂ’ve watched this presentation youtu.be/E0yZdLkpvR0 some while ago and these guys did some extensive research on this transmission. They say it can handle even 475lbft although itÂ’s rated by the manufacturer dor a lower torque (I think 400lbft). But taking into account itÂ’s now over 30 years old and 130k miles, I thought something like 400lbft would be better for reliability. Anyway 12% over 400lbft does seem a huge step, it could be safe.
Another problem can be the the C beam, but that basically depends on the output torque not input (engine) torque and I think can be a problem if you use drag tires even with std engine, 1&2 gears can generate enough torque up to race tires traction break up.

What I read is that the 92 and earlier ZF6's were German made and rated for 450 ft-lbs. GM licensed the design and in 1993 began making their own. They changed the design of some of the helical gears to lessen gear noise and then rating dropped to 400 ft-lbs.

I also came across a thread where corvette owners were successfully drag racing with the Dana 44 differential and laying down some low 60 ft times. Not sure is you have Dana 36 or the Dana 44 but the 44 sounds strong. I did find info that said the 1993 and later Dana 44's were somewhat stronger.

I think you are being overly paranoid about breaking stuff. Install a good clutch and drive the car. If something breaks upgrade it.

[sanderson231]

C beam upgrade:

https://www.corvetteactioncenter.com...e-beam-plates/