GREGGPENN

Many of you have noticed I went from a 350-build to a 383.

(Couldn't get myself to dish out the $3000 for a shop to do the engine, clutch, and shifter work -- so I opted to find a local guy to help me with the work. Since payment will be my 55k factory motor, that left me extra dough for a shortblock! Instead of a 55k 350 with headers, heads, intake, and cam, I'm doing the WHOLE motor.)

In prep for the 350 build, I spent hours and hours porting, siamesing, and (exterior) polishing a sweet SLP TPI setup. The intent was to do a modified SR setup w/o dealing with that discontinued piece. Plus, I really, really like the look (and potential powerband) of this setup.

Now that the intake is done and I find myself squarely staring into 383 power levels, I have to reconsider my choice. Problem is most people running added power may not understand the usage which I intend.

If I had an automatic, I would certainly avoid the SLP/TPI setup and install the HSR I also have. That's because automatics will double-downshift under high demand,,,plus the torque convertor adds to their low-end leverage. But I have a ZF.

My intent is to drive my 383 with single downshifts. And, I like driving more in the mid-rpm ranges better. I like the feel of big-block torque and the 383 should provide that quite nicely. I'm just not sure if/where too much torque would cause traction issues. Many people have suggested the SLP/383 is too much torque -- but they have track experience and run automatics. My interest is a bit different.

I want to drive by downshifting to 2nd out of corners and to 3rd on the hwy for "passing gear". Gearing leverage will be slightly less because of my higher gear selection. But the gearing of a ZF adds an extra gear over an automatic that makes my style/approach less dumb than you might think.

Doing a spreadsheet on my situation shows a modifed SLP intake will provide optimum torque using shifting described above. If I go with the HSR, I'd need to downshift to 1st under 40mph or 2nd under 60mph to enjoy the same level of torque. I really don't want to do that.

With that in mind, I'm trying to decide of the rediculous projection of 500ft/lbs of torque at mid-range rpms will constantly spin 315/35 tires all day long (3.33 gears). Again, I'm talking about using the technique above w/o revving and dumping the clutch to add add'l torque. I'm talking about downshifting, fully engaging the clutch, then stabbing it for short bursts. This is strickly for street fun -- with no intention to ever run it on the track.

Believe it or not, simulations show midrange torque could be up to 100ft/lbs higher than LS2 mid-range levels and 40ft/lbs higher than LS7 mid-range torque. (I've only driven an LS2 and felt more midrange would be nice to have. Just not sure how much. LOL)

Obviously a HSR would be faster on the track -- but why build for something I don't plan to do? I want a car that feels boosted. (Unless it's over-the-top. That's were I'd switch and extend the powerband with the HSR to create a more usable powerband.) Hopefully, people who experienced this level of torque -- with a stick shift can suggest whether it'll just be too much. And, I need to start polishing up my HSR! LOL

gp

FWIW, Here's a couple of pics of what I'm reluctant to leave unused (and sell) after the build.

frenchyoliver

Your setup is absolutly stunning with your 383. I would keep it this way...
But 500ft/lbs sounds unrealistic.
Nevertheless If you decide to sell I will be on the list.

Seems you have worked a lot on it. Your runners flanges look marked and a lot scratched.


Talking about torque , I just tried this morning the new mecedes 450 CDI with 780 torque at 2200 tr/mn...
With the new 7 speeds robotic gearbox, experiencing such power was amazing.
It made me feel my L98 was like a japan small four cylinders when I went home after test....

SurfnSun

There is no such thing as too much torque unless you get it and peak too early.

Personally Id do the stealth ram and 3.73-4.10's. That will take care of your downshifting problem and your car will be faster thru the whole band.

frenchyoliver

With 3.73-4.10's, arent you to fast across torque range ?
Plus SR, isnt that too high for open roads?

STL94LT1

With the right tires 500 lb/ft of torque should be very managable. My C5 is pushing 600 lb/ft of torque and is controlable (most of the time) on the street.

powerpigz-51

If I were you, I would run them both. Start out with the LTR set up. It seems you have a lot of thought and work into that set up, and I would love to hear about the end result. I will be running a similar intake on my 4+3 flat tappet 355 with Edelbrock heads. That much torque on a 6 speed street car sounds like a blast. Then if you are disappointed in some way, you can always switch to the HSR. I want stupid torque! (I also secretly want too much wheel spin).

GREGGPENN

At the ground...it would be optimistic. But my build should be as good/better than this:
http://www.superchevy.com/technical/...t_results.html

The enlarged/siamesed SLPs should help improve top-end roll-off and equal/better the runners used in the article.

With adjustments for exhaust and accessories, my projection drops to 417hp/487tq (which is my comparison to GM LSx numbers btw). Obviously less than that would make it to the ground. So, the actual rwtq would be 440-450ish? (Which is what I'd be looking to hook on street tires.)

GREGGPENN

I think that's a reasonable point. If I pick 3.93 gears (in the middle of the range above) and do a chart, it turns out that the results could be similar (maybe worse).

Shifting at 6000 rpms with 3.93's works out to be the same as shifting at 5100rpms with 3.33's. IOW, the mph when shifting would be the same (in all gears). But, I figured my shift point would be closer to 5500 rpms,,,5400 at the lowest. With 3.93's, it would take 6500 rpms to equal that shift point (MPH).

With an extra 10-15% torque using a TPI, it might just offset a 10-15% gearing change. The feel and time getting there might also be the same. I'd rather save the money and keep my gears!

Aurora40

500 lbs-ft in 3rd gear is the same wheel torque as 240 lbs-ft in 1st. 500 lbs-ft in 2nd gear is the same wheel torque as 335 lbs-ft in 1st. So it's unlikely to burn the tires off in 3rd gear. 2nd, you might have some breaking loose depending on the situation.

The lack of mechanical advantage is a pretty big tamer of that torque. I think you'd need to have some insane forced induction kind of torque to have issues in 3rd and up.

383vett

Gregg, I think you are trying to overthink this. For what you are doing, just build the motor with the broadest flattest torque band you can and the rest will take care of itself. If you're worried about spinning your tires, there is nothing that says the right foot needs to be planted to the floorboard. Nice work on the intake.

GREGGPENN

Yeah,,,I really didn't expect to have problems with 3rd gear or higher. And, regardless of the intake 1st gear will need to be feathered. 2nd gear is the biggest question.

The bonus question is whether the HSR would put down enough torque to make me go ga-ga. An M6 LS2 I drove was nice, but not ga-ga material. I've been trying to figure out how much more torque (over the LS2) it would have taken to be really fun and/or break the tires loose TOO easily.

An HSR costs an extra $300 for the dizzy/fuel lines. The SLP doesn't and is "ready". I know the track guys would pick the HSR (as they should). I'd go the opposite route with the SLP -- if I can hook it fairly well. Street builders might have a better handle on that aspect. For one thing, racers rarely use sticks.

GREGGPENN

Your statements above say use the HSR. What if,,,instead of being worried about spinning the tires, I'm worried that I won't feel my $6000-$7000 bought me enough torque!

(I don't care how fast it can go in the 1/4).

Pete K

Build max torque, and buy better tires

GREGGPENN

This is the crux of my question. Because I don't go for maximum mechanical advantage (with the lowest gear), I want extra torque to make up for it.

For track conditions, 1st gear would be required at 25mph and 2nd gear would be required for 45mph. 20-25mph is approximately the speed coming out of corners on the street. 45 is about the lowest people see on the hwy for "passing" launches. I'll use 2nd and 3rd for those conditions. Mechanical leverage will "kill" some of the fun because of my gear selection. And, that's the thing most people won't get when reading this thread.

My gear selection could be described as passive aggression!

LT4BUD

I really think you should be looking at the horsepower curves as a basis for selecting your gears to get in the max hp range at the speeds you desire.....

This was discussed extensively in a previous thread..


http://forums.corvetteforum.com/c4-t...vs-torque.html

More horsepower is always better...just need gearing to get in the power band at the mph you will be racing...rear wheel torque and horsepower go together...don't get tricked by motor torque

rodj

I think you would be impressed
You have seen the intake comparision
http://www.compcams.com/Community/Ar...?ID=1737510521

pologreen1

HSR is the best bet with that hood already in place.
anything else is a waste of time, except a min and REAL low gears.

l98tpi

http://www.compcams.com/Community/Ar...?ID=1737510521[/QUOTE]

Don't let the L98 bashers read this!!!

Aurora40

And that's why I was saying it probably isn't too much torque.

I didn't quite follow your "single downshift" thing since you said you'd go to 3rd for highway passing. If you meant shifting from 5th or 6th to 3rd is a single downshift, then it seems it's a statement with no real meaning, as it doesn't rule out aggressive downshifting (i.e. 6th to 2nd for highway passing).

But for what you described as conservative downshifting, the more torque the better.

Aurora40

It sounds like he is trying to intentionally hamstring the gears though, as that suits his driving style.

If your constraint is that you will always be in a tall gear and in the low-end of the power band, then presumably it would be better to have a motor with a strong low-end.

I don't quite follow why that constraint is imposed, but different strokes...