Okay, I just picked up a '91 TBI formula...a truly beautiful car, but the performance is dimsmal compared to my other TPI car...

Anyways, I've read the ultimate TBI stuff, and am curious of the actual power gain (#s) that you all have achieved.

I will definitely do all the UTBI mods, and also want to change the cam. Consensus says LT1 cam, but 1 or two other seem to have the LT4 version. Obviously the LT4 is the more aggressive version, but how do the two compare in terms of real world power and driveability? I have a B&M TC (2000 rpm stall) sitting around that I figured I should also use. Any opinions on how this may affect cam choices?

I also have a dual cat y-pipe and 3" exhaust system laying around I am going to throw on.

So w/ the above, are we talking somewhere in 250-275 HP range?


Thanks for any info...

MILT

 

Well, the looser convertor will want a bigger cam. The LT4 cam specs are: 203/210 duration @.050 and .476"/.480" lift (with 1.6 rockers). I looked around a little bit and couldn't find the specs on the LT1 camshaft, but I think that it's a bit smaller. I'd go with the LT4, especially if you're gonna do some intake/exhaust modifications to go along with it.

 

The Lt4 is a good cam.
While you're doing the y-pipe and exhaust you should try and install some larger exhaust manifolds or headers. The TPI manifolds are slightly larger. As for the ultimate TBI mods, please PLEASE make your fuel pressure regulator adjustable. Your TPI might be MAF but TBI is speed density and anything you do to free more air will require you to manually help with the fuel delivery. Go to my website and do the adjustable fuel pressure regulator while doing the other mods!
The heads on the Lo3 are crap compared to the Lb9 and L98 so understand that you can't really get huge hp from the motor unless you do heads and cam. It's like a package deal. It came from GM with all crappy parts so do piece by piece. I'm honest when I say the only thing I like about the Lo3 is the flat top pistons and how well it responds to N2o.

 

Heads made the biggest diff along with exhaust...but then again I did heads and intake and 1.6 rollers together.

Good luck

 

Thanks a lot for all the help guys. I think I'll skip the heads for now as I'll probably end up either selling the car or installing a new motor sometime in the next year or so.

Oh, forgot about computer chip mods. Obviously a new chip would get the most from the mods, but will the car run *well* w/ the stock one?

MILT

 

does it really take n2o pretty well? i was thinking about getting it so i could actually win a few races but i still havent decided...if i am gonna get n2o is there anything i should do to prep the motor?