Jay

iTrader: (2)

First off let me start by saying this isn't the usual "who would win" type question. More of an overall driving experience comparison.

The cars in question are both my girl friends. Her daily driver is a low mileage 07 Impala SS with the 300HP 5.3L. Last year I picked up the 91 Z as a parts car but she developed a soft spot for the car so I've been putting it back together for a nice weather fun car for her.

As purchased it had a tired low output carb 350 that was in rough shape. Originally I planned to put the TPI back on the 350 and call it a day. Unfortunately the engine had a broken piston, and weak heads, and who knows what for a cam.

I picked up an LB9 out of a 91 G92 5 speed car for next to nothing. I don't want to drop a ton of $ into the car and the 305 is staying. It was an LB9 car from the factory. It will eventually get the 350 from my IROC when I get the new engine built for that. But for now this is a low $ project. As it stands I have less than $500 into the car including purchase. Most of the parts going into it were left overs from other projects.

The car is an automatic, and that's not changing. The 700 was put together with a setup from Probuilt and has a 2600-2800 converter. It's brand newly built and never been used. Plus she doesn't know how to drive standard and has NO interest in learning. Currently the car has 3.08 drum brake rear, but I have a spare 92 3.23 disc rear along with 3.42 and 3.73 gear sets to choose from, and a zexel torsen from a 02 4th gen.

Other "mods" AC delete, smog pump delete (previous owners got rid of everything), 1 5/8" shorty headers, high flow cat and 3" cat back.

The dilemma is, I want the Z to be fun. I don't expect it to be the fastest or quickest but I don't it to be a let down compared to the Impala. Would a cam upgrade and or 1.6 rockers or any other minor add ons be worthwhile? I had planned on using the 3.42 gears, but toyed with the idea of the 3.73s. It doesn't have to actually BE faster than the Impala, but at least feeling more like a muscle car.
I've driven my friends 91 Z28 convertible with the 3.08 gears auto and supposed "peanut cam" and was underwhelmed.. though at the track it was not far off from what the Impala did.

Thoughts comments suggestions ideas?

yaj15

iTrader: (3)

If you intend on sticking with long-tube-runner stock style TPI 3.42 gears are the deepest that you would need to go. TPI's main goal was to produce a lot of low and mid-range torque and horsepower - from idle to around 4,500rpm in stock form. You can modify that basic set up to push the power band to 5,500rpm-6,000rpm but that's not TPI's main goal. Long-tube-runner style TPI set-ups don't need steep rear gearing to perform well.

If you had an LT1/mini-ram style intake set up you would stretch your power band in to the 6,000rpm-6,500rpm band. Then you need to start thinking about 3.73's or steeper gears since the motor will me making more torque and horsepower where the factory TPI starts straining for air - after 4,500rpm.

Follow GM's lead. The most potent LB9/700r4/rear gear combination came out in 1985 - you could get an LB9/700r4/3.42 geared IROC and it was a quick car back then and still performs well now with not to many modifications.

The highest performing LB9's from 1989-1992 came with the L98 cam, G92 gearing (3.42-10bolt or 3.45-9bolt) paired with the T-5 manual trans.

You've got aftermarket high flow exhaust from the headers back and a high stall converter with a built aftermarket trans. Your stall speed is a little high for a stock TPI car but you should have good performance out of it still.

Now it's time to address the intake side. Make your own cold air induction kit or buy some Hawks ram air boxes. Cut out all the baffling below the stock air box and run some tubes behind the fog lights and connect them to the gutted out air boxes. If you haven't already done so install some high flow aftermarket air filters.

Next I would look in to some after market TPI intake parts - ported plenum, 52mm aftermarket throttle body, aftermarket base. All of these parts will transfer over to your new 350 motor when you get around to it. Also the LB9's got 19 lb/hr fuel injectors and the L98's got 22 lb/hr fuel injectors from the factory. When you switch over the the larger 350 motor you will need to upgrade your injectors as well.

Also upgrade your ignition components and make sure that the rest of the car is in good running order as well. I'll take a 100% stock car that is in good running order over on that's modified and runs like crap any day!

Make sure your suspension is in good shape too. Poly bushings, good shocks, etc. Think about an aftermarket torque arm, boxed lower control arms, boxed panhard bar and sub-frame connectors. These cars should have come with sub-frame connectors from the factory. The floor is the only thing supporting the middle of these uni-body cars and when that gets met with some power, hard straight line acceleration, or canyon carving exploits the weakness in the factory chassis is on full display. Sub-frame connectors really do make a night and day difference in the stiffness of our thirdgens.

You can make all the power that you want - if you can't get it to the ground in an efficient manner you will just sit and spin tires.

Make sure your brakes are up to task too. If your lucky enough you can find a G92 car or a G92 10bolt from an LB9/T-5 car in the junk yard from 1991 or 1992. That would give you posi, 3.42 gears, and the larger rear brakes with PBR style calipers. You can upgrade your front brakes for not that much money to the 1LE set up or a Baer brake kit.