LT4 dyno/track results for LT1/LT4 bolt ons? My quest for a six speed C4 continues....

[BIGBADJOHN]

Hi all,

Well, I am in the thick of my chase for a 1992-1996 corvette, but since it is Easter and since it is raining cats and dogs, I have yet been able to put the laptop down to go out in search for my vette to be. I have a lead on a few (all 6 speed), including a 1996 CE with the LT4 engine and 50k miles, a 96 black coupe with the LT4 option, a red 93 coupe with 48k miles, and a dark red 92 with 50k miles. All are less than 20k, with the 92 being all the way down at $16900. I am stoked!

Anyway, on to my questions. I have been poking around on some corvette forums and chevy related performance parts houses, and have gotten a general idea of bolt ons available for the LT1 and LT4. My mod budget will be VERY small when I get the corvette, but that's ok because I want the car to remain as stock as possible for resale anyway. Nevertheless, small mods like the TB airfoil, vortex intake or cut stock airbox with K&N filter, MSD 6AL ignition with coil and wires, hypertech programmer/powerstat, and possibly headers or even headers and catback exhaust could qualify as mods that won't break the bank and can be easily removed should I want to take the car back to stock. Here are some questions I have for you all regarding the more common bolt ons that I have mentioned above:

1. Does anyone have any before and after dyno data or track test data for any of the mods I have mentioned above? I am VERY interested in seeing any of this, as it could potentially save me lots of research and disappointment when I get ready to mod my corvette...its out there somewhere calling me now.

2. How well do the more common bolt ons work together? Could you recommend a "suite" of minor bolt ons (short of major work like heads and cam or supercharger) that work well together to wake up the LT1 or LT4 corvette and shave, say, half a second on the e/t?

3. Coming from a background from ford products (namely the SVT contour and Mustang) I know that some great bang for the buck mods include a bigger MAF/throttle body, aftermarket gears (3.55 for a street stang to 4.10 for a mod motored cobra bracket racer) and even a small single stage dry nitrous kit (adding a 100-150 shot can have a great impact on E/T). Are these also mods that are relatively inexpensive for the corvette?

4. Perhaps the ultimate easily removed bolt on modification is a dry nitrous system from NOS, nitrous express, edelbrock, etc etc. Does anyone have any experience with adding conservative amounts of nitrous to a stock or near stock LT1/LT4 corvette? Not that I would do such a thing, but it would be a cheap (although relatively volatile) way to see 12 second e/ts.

Thanks in advance for your input as it will help me get a feel for gains I can expect, how far I should go, what I should budget for in the future, and feasibility for mods to work together without adversely affecting the car's longevity or driveability. Thanks.

 

[vetsvette]

Mods?

Before you start talking about mods maybe you should try an LT4 out first. I don't think you appreciate the difference between that motor and your SVT. There are any number of mods available but you are looking at over 330 HP to start with. And once you get used to driving it you should not have any problem getting into the 12's. If you can get a LT4 CE for less than 20K I suggest you jump on it. If you can get any LT4 (in good shape 0f course) for less than 20K you had better check it quick because it won't be around for long.

 

[BIGBADJOHN]

Thanks for the reply.

I totally appreciate what you are saying. Comparing the SVT contour to a corvette is like comparing a stock Z-71 pickup to the GOLDBERG monster truck. There is no comparison.

That said, I will let you know that the SVT contour is not the kind of car I am used to driving. Its a high strung front driver and not exactly what I would call a muscle car. I'd put it up against a 328i anyday, but I have decided that the sport sedan craze is not for me (too yuppie). Most all my other cars have been muscular v-8 coupes...not exactly corvettes, but still strong. They include a modified 1994 Thunderbird (ran high 14s despite crummy ford 4r70w automatic and 4000 lb heft) 1994 Lincoln Mark 8 (285 hp luxo barge that just "happened" to be able to lay down 40 foot black stripes wherever and whenever). and my personal favorite and first car, a 1971 Chevelle malibu with a strong 350 and powerglide tranny. I am no stranger to frame twisting torque and instant sideways fun.

Anyway, I don't want to go crazy with modifications, but part of my enthusiasm about cars is the ability to work on them and see the gains from my efforts....which is why I am asking about the modifications. Is there a search feature on this forum? I should start there but haven't been able to find it yet....

Any info you all could provide would be great.

 

[Trance_LT4]

To answer your questions, as best that I can.

#1 I didn't dyno my LT4 bone stock, but they average about 280-290 hp at the rear wheels in stock form. With only flowmasters exhaust system for mods, I dynoed 305 to the rear wheels.

In that form, it ran 12.9 @ 109 on reg. radials.

#2 Since then, I've put a conical K&N system, MSD6a (you don't need an MSD 6AL since your vette is going to have a rev limiter on its own, the 6AL will cost more initially, and to change RPM pills) MSD wires and coil, TPiS Air foil, MAF descreened, and coolant bypass.

In this form, the car runs 12.5 @114 on reg. radials

#3 I also come from the mustang world. The same idea behind their mods works for us, better air flow in and out, better spark.

The flowmasters were my most expensive mod, at $600 for the system, but I think they did the most. LT4s are rated (but we all know how ratings go) at a 13.7 from the factory, and with just the flows, I ran 12.9. All my other mods were very cheap, some free, and combined they dropped another 1/2 second.

With a Hypertech programmer to maximize the programming, and to lower the fans "on" tempurature ($350) a bigger MAF and 52 mm throttle body ($200 and $350), I should be low 12s, even high 11s if it works they way I think its gonna work.

#4 I can't use nitrous myself, because of strict maryland laws regarding nitrous systems and street vehicles, but I only see one problem. LT1s have a high compression ratio (10.5:1) and LT4s are even higher (10.8:1). There is a higher tendencey of the engine to detonate with nitrous, especially with high compression, unless you take away timing and run better than pump gas (octane boost from pep boys won't solve the problem). You will also have to change to a colder spark plug. With all these changes, plus the $600 or so for the nitrous system, $300 to install (you'll want a pro to do it, and make it look clean) the small 75hp shot you'd be able to run on 10.5:1 or more CR.......nitrous won't prove to be as worth the effort as it did on your 5.0

Like I said, a few simple add-ons, on a bone stock (top end and bottom end) LT4 , and you will be comfortably in the 12s.