macx

When you get done laughing, consider this - I'm researching / planning a
383 targeting a fat & flat & broad torque curve for a mild stall performance
700R4 (wide ratio spread) in a 3400+lb car with 3:08's. I like the reverse cooling of the LT1 design and the fact you can still stroke it without the cost of an LS1 type motor. Also definite on port efi. However, the stock LT1 efi intake is just an open box plenum with short runners - definitely NOT a low/mid range torque manifold by any stretch. GM makes an LT1 carb dual plane intake for swaps that looks a lot like a Performer RPM, and says it adds 30 lb ft to a stock 350 inch LT1.

By converting to port efi and using either the GM LT1 system or something like
DFI or FAST, should be just the ticket for my target of fat torque from
2500 up with a torque peak of around 4k & hp peak of just over 5k.

Has anyone ever tried this intake on an LT1?

Thanks!

John W

Since this hasn't seen any comments, I suppose I will lend my $0.02. I did a bit ofresearch since I was contemplating building a carbed LT1. It looks like any sbc manifold will fit, but an adjustment for the bolts needs to be made (bolts are at a non-standard position). Many folks just drill them out at home using the intake manifold gasket as a guide.

The beauty of the stock LT1 intake manifold (over say a TPI setup) was that the short runners allowed it to rev. Your wishes (high low rpm torque and max of ~5000rpm) sounds like you want a TPI type manifold.

When you say "fat" torque curve, I am guessing you mean flat and broad? Check out this link with some dynos of a stock LT1 intake and stock cam/LT4 HOT cam combination. It don't get much flatter than this. A 383 is going to have even more torque.
http://forums.corvetteforum.com/zerothread?id=623117

A good first step would be to ditch the 3.08 and step up to 3.42ish gears. Most folks with autos lilke that combination.

What are you looking to do with this engine? Perhaps we can point you in the right direction.

John


[Modified by John W, 2:35 AM 8/11/2003]

macx

This would be for a daily driver 82 - mixed 60mph & 75 to near 80mph.
With 255x60x15's at a rolling dia of about 24", it would hang around 2k or
plus a couple hun at road speeds. I compared the 7004R 1st w/3:08 to a 2004R w/3.23's and the 700 combo is a lower 1st but such a wide 1-2 spread. Then a nice man wrote in the forum about 700's having less internal inertia, and other advantages, so if I can really pump the low/mid range torque, it would work well (using about only a 2200 converter, letting the torque work) Also no conversion hassles, just a better later model case onto the stock Vette tailshaft/housing (I do all my own work). Then I found that I can't find anything between 3:08 & 3:54 for the D36. Not wanting to run closer to 2500 at near 80, that reinforced my wide ratio 700 w/3:08's. I've read a quite a few dyno reports on various 383 combo's, and using AFR 190 heads, Comp Cams HR in the 224 to 230 intake range at slightly over 500, I've seen a number of 9.6cr 383's put out 425 to 440 torque at 2500, with peaks near 500 at around 4k. The best ones just about universally also used RPM Air Gaps, which are said to be just a small tad (single digits) better than the Perf RPM pretty much across the board. CC makes an LT1 specific hydr roller around the 220/500 range. I've read a bunch about the adapted dual planes, and looking at pics it could be done but I'm wondering about the access mount bolt location. Want to keep it clean & no hassles, and if the GM LT1 dual plane is close to an Air Gap, sounds like the way to achieve that. Of course, would convert to port efi, using either the GM system modified, or a DFI or FAST type setup to enhance driveability and throttle response at street rpms's, with the plus of relatively more liveable mileage. Lingenfelter made some monster torque motors using pretty much the same setup with efi and sometimes the SuperRam, with torque peaks at/under 4k. The TPI engines seem to sign off not much above 4500 even with the entire aftermarket large base/runners deal, which would be exacerbated with a 383, and both they and the SuperRam still have the not so good entry angle from base to ports. Not to mention they're quite a few hun $ more, even considering converting. A good hi-rise dual plane has longer runners than the stock LT1 by a bunch - and not too much shorter than the SuperRam. The most successful (wide, flat torque) usually had Air Gaps or Super Rams. I'd go something like 3:23's if they were available, but without them, want to stick to 3:08's for the hiway. BTW I'm not so much into the stoplight grand prix as I used to be, but still want the capability to blow the doors off the occasional jerk driver when I get the urge. Oh, and thanks for the comeback. Didn't figure
I'd get many responses, just "threw the hook into the water" just in case.

redvetracr

macx, If you or anyone else is interested I have two NOS/GM in the box LT-1 intake manifolds these are the later (refined) intakes both different part numbers and both discontinued by GM many years ago. e-mail direct for part numbers. redvetracr@msn.com

John W

Macx,
Talking about accessories. I think that you will have to use LT1 specific accesories and brackets. The LT1 uses a water pump driven from the cam sprocket, all LT1 equipped vehicles used a serpentine setup. The serpentine setup varied from model to model (F-body, Y-body, B-body), this adds some additional cost to the swap.

You may want to check out the camaroZ28 forum at: http://web.camaross.com/forums/ . There a good number of folks who have built 383s and you can see their "recipes" and results. Since the LT1 is reverse cooled, people have had good results running dynamic compressions of 9:1 (usually static compressions of 11:1 on up). The info that you have found for sbc buildups is a good starting point, but it needs to be modified to take advantage of the LT1s peculiarities.


John

macx

I've found you're absolutely right. I've recently
done a lot of reading, lately focusing on the LT1
and like what I've seen about the advantages of
the reverse cooling, coupled with the still reasonable
cost of stroking to 383. Some problems with the
opti unit but also have found some fixes for that.

Have also found that it would be good to start with a
complete engine to get all accessories & mountings.
However, it has to be Corvette specific so that the
access & mounts fit into the 82 chassis (which reportedly
also then gets me a 4 bolt block). Would then
sell the top end (heads/complete intake setup) and the
complete reciprocating assembly to offset the AFR's,
intake, and 383 kit (looking at Scat cast crank, 7/16's
cap screw I beam rods and Speed Pro coated pistons).
Have found some sources for complete used engines incl wiring
and all access, and likely could in my own area with
some searching. Also, then, "standard" 82 small block
82 headers will work (angle plug). In general, the
swap would be considerably cheaper than an LS1,
even without modifying the LS1 intake/cam/improved heads/
headers etc, and a 383 LT1 would be close enuf in performance
and better in lower rpm torque (and likely better for a 3:08
gears in combo with the wide ratio 7004R) when considering the
increased stroke and overall a good return for the investment.
(In other words, I might even be able to afford it!)
Besides, half the fun is planning and researching diff. combos
to get it "just right", and then doing the wrenching!
Thanks for the input.

John W

For reference, I paid $800 for a f-body LT1 longblock about 3 years ago from an individual. There is a web site LT1s that run that seems to specialize in "modern" engines http://www.lt1sthatrun.com/ This company would be a good reference point for cost.

John

macx

Hey, thanks for the link! Looks like they've got a bunch of 'em!