We autocross our '93 in various SCCA and road racing events and need to keep within certain boundaries or we jump classes. However, we are needing to gain a little more HP to compete against the LT4s in our same class. We have already changed out to high-flow exhaust, K&N filter, hyperchip, 160 deg thermo, etc.

In looking at parts, we notice that '94 has changes on items like Throttle Bodies, Injectors, etc. - does anyone know if this is due to performance changes in the component or it is it due to the programmable eprom?

If it is a performance gain, we would like to pursue installing the '94-'96 LT1 Throttle body, 26#/hr injectors, etc. on our '93 LT1.

Are there other parts such as rocker arms from the LT4 that would be interchangeable with our LT1 without tearing into the engine?

We are desiring to find enough minor changes to hopefully gain about 20-25 HP.

Thanks in advance for any suggestions / advice anyone has.

 

The injectors and TB aren't going to gain you a thing. The LT4 rockers are 1.6 ratio and will increase your valve lift. There's a real gain there. Assuming you're running a class where you have to stay pretty stock, this and some tuning may be all you can get away with. With both, you may gain 20 ponies or so. You'll need to upgrade your valve springs to the LT4 ones, at least. I'd recommend something even a little better for hard running.

 

Theres no gain to be had in injectors. You can go with a factory TB bored to 52mm for stealth but a 94+ tb is the same size with the exception of the LT4's.. I can pick you up about 15 hp over your hypertech chip if your interested.

 

I'm interested in gaining the HP, tell me more?

 

Put a set of 3.73 gears in there and youll be as quick as they are.

 

the gear change would change our class - can't do that one

 

Your pretty much stuck with 1.6 RR's as the best bang for the buck.Nothing to gain in the intake without exhaust and cam changes.It breathes well stock.Alvin can take some datamaster scans from you and do a good mail order tune to gain a few ponys but with out an exhaust change you will be lucky to get 30fwhp with the tune and RR's.If you can use it there is always some debate about a cut lid air cleaner with a K&N filter.I doubt it will help much with a totally stock exhaust(which is really not that bad).

By exhaust I mean LT headers of course cat backs help a little but LT's are better(no sense in using shorties either).

 

I'm wondering how in the world they would know? I raced cars for about 15 yrs. and tech at most tracks is a joke!

 

If you want to gain some good ponies you should just bite the bullet and get you self a LT4 cam, Heads, and Intake manifold, etc. I know it's a few bucks, but you can always sell your old parts! I know a guy who has a few sets if your interested!

 

I have been looking at the LT4 Hot CAM kits in JEGS... I am interested in pursuing that option as well.

 

A good choice but you indicated your concern about changing class.If your going that route Ported heads,Cam you will need a new opti as the GenI will not fit after doing the cam you will have to upgrade it to a 95.

 

This isn't true. I have the Hotcam kit with the original style 94 opti.

Now some say it is highly desirable to upgrade the opti, timing set, etc. But it's not necessary. I spin my car to 6500 but then I don't race it weekly. The single roller LT1 timing set is not exactly garbage.

 

I thought all you have to do is grind the pin down on the hot cam for it to work on the opti???

 

that is correct, i have the hotcam kit in my 93 and it runs fantastic. cut the dowel with a cut off wheel. idle is almost stock too. if you want a nice lope at idle go with a comp cams 306. if you want something real radical go with the gm847 cam.

 

Just remember that if you are serious about auto-X, if someone wants to protest your car, there is a procedure and if you get caught you lose. Having an idle that rocks the parking lot is a good clue that you are not stock. All tech does is make sure your Vette is safe for competition. Other Vette drivers can spot cheaters easily. A good set of headers put me in the street prepared class. It's pretty easy to spot headers on a stock Vette. Just so you know. Now if all you want is braggin rights in your group, go for it.

 

I am assuming that you are running BSP in SCCA since the hyperchip isn't legal in stock. Also in stock you can't update or backdate to different year parts, so the valvetrain stuff isn't legal either, nor is the bigger throttle body. For BSP best thing to do is bring your engine to an LT4 spec. If you do pieces and parts, that isn't legal in BSP. You can basically update and backdate the engine as a package, but the engine has to be stock from the intake manifold flange down, for whatever engine you claim it is. That means that if you claim the engine is an LT4 it has to have all LT4 parts in it. You can't just change the rockers in an LT1 to LT4 rockers if the cams are not the same. Hope this makes it a bit clearer, but there is a right way to do it. When we were running BSP we got an LT4 and had it blueprinted. We were making about 400 hp at the flywheel in legal BSP trim.

And Gar... In autocross it is obvious if you have a gear in it. Everybody is watching you and they can hear your shift points and know when you are or aren't hitting the rev limiter. Then when your competitors makes a run everybody sees where they are shifting and then it is more than easy to figure out if somebody has a gear in it. In short, it is obviouls enough that you likely wouldn't get away with it. Since it is easy to count input shaft revolutions relative to tire turns there isn't going to be a teardown fee. For the small protest fee, if they suspect there is a gear in it, it is gonna get checked. If you aren't beating anybody, nobody is going to care, but when you start winning expect the paper to fly. In a serious autocross you would be found out in about 30 seconds, or about as long as it takes to make half a run.....

While power is important you are probably better off to spend the money on wheels and tires and improving the handling. Handling counts more in autocross than power. A good LT1 with a six speed has most of the poke it needs, and you won't give up much in terms of run times to even a built LT4. If you can gain some grip, and work on the nut behind the wheel, there is a lot more to be gained than if you added 20 hp. Springs, swaybars, and most importantly shocks will make you a lot faster than 20hp ever will.

 

Points well taken... to keep points too

Sounds like I need to locate a good used LT4 engine or start buying lots of LT4 parts

Just curious, does anyone have the stock specs on an LT1 cam for the '93 - I'm having trouble locating that data.