I have a 52mm Holley TB sitting in my garage forever. Any one try Holley?

It's a stock 305, but I should see some gains considering the stock one has 80,000 miles on it.

 

If you get 1 hp out of it i'd be surprised..

 

There shouldn't be any real gains on a stock LB9. The TPI system was designed for 305 motors to begin with so it's not as much as a rescriction as with the L98 motors.

When my L98 was all stock I installed a BBK 52mm throttle body. The gains weren't that much but it was noticable a little. Now I'm in the process of having all of my aftermarket intake parts ported, that throttle body will really be helpful.

Does your LB9 have the L98 profile cam or the low lift peanut cam? If you have got the lower lift cam you should at least consider installing a cam with the same (or simular) profile as the L98. That low lift cam will really hold you back on how well your other performance mods will work out.

 

I have the T5, so it's probably the bigger cam. And the have the 3:45 gears. It's a torque monster.

 

just because it makes a lot of torque doesn't mean it needs a lot of air. Even on my well modded TPI 350 Corvette, replacing the 58mm throttle body with a stock 48mm resulted in no change in power. The only change it made was that part throttle power "felt" different because for any given amount of pedal input, you're actually letting more air in, but since the car's maximum air requirements were still below what the 48mm could provide, there was absolutely no change at WOT.

 

Thats great news. So you have 1989 IROC with the LB9/T-5/3.45 posi rear combination.

Since you've got the most potent factory LB9 drivetrain combination I would start moving in to exhaust and intake mods. One mod done alone won't make a big difference but an entire system will.

Look in to some headers and exhaust. After I did that to my car it really woke up. The stock manifolds on these cars (even the TPI cars) really suck in terms of performance for lack of a better word. Headers, y-pipe to go along with them, high flow cats, and a cat back exhaust will really open your car up. Should be worth around 15hp and 15 pound feet of torque.

Next I would go after the intake. You can make a cold air kit cheap for TPI Camaros or buy some ram air boxes from Hawks Thirdgen. You want to get some duckting that will start from right behind the fog lights and connect to the bottom of the factory air box. Cut out all the baffles from the bottom of the air box and install aftermarket airfilters and that will really make a difference - even on a stock TPI car. I've done this to my car and it make a small performance increase - the stock TPI becomes the limiting factor there. I had better throttle response and better top end power from 4,000rpm up to the red line at 5,500 rpm. Even below 3,500rpm (where you drive most of the time on the street) there is an improvement in terms of performance, its just more apparent at higher rpms.

These mods are cheap and will really pay of latter if you decide to install some after market TPI intake runners, base and port the plenum.