I got a 91 Firebird 305 tbi. I was wondering if I could get a little feed back on some basic mods I could through on it. I have already switched to an open air element, what do you suggest I do next.

Rats91

 

1. Ultimate TBI mods in the tech articles of this site

2. GEARS and posi Check out the SLP posi. http://www.slponline.com/view_produc...TNUMBER=64501T

3. Then replace exhaust from the engine back using headers and cat-back for a TPI car since it has 3" exhaust instead of 2.5" for the TBI system.

 

Posi & Gears
Headers, Cat, exhaust
K&N Filter
Ultimate TBI mods
Change Timing

That should be a good improvement from stock.......

You may also want to try and do the weight-reduction mods to save some rotational and dead weight.....

 

Do gears and posi (if not equipped) last. Do the exhaust from engine back (headers, catback), then maybe new intake manifold (4bbl -> TBI adaptor plate) and an open element or dual snorkel intake.

Good luck.

 

What ratio is the best?

 

I would say 3:23 if it's a mild street car, so that way you can keep the highway driving with the good gas mileage........

 

Depends on what you want to do with the car.

3.42 is a good all around gear that cruises nicely on the interstate at 70+ mph.

3.73 is good if you are going to run at the track more. It will run around 250 rpms higher at 70 than the 3.42 and will thus cause more interior noise from the exhaust.

It will also depend on the modifications done to the car. Stock engine puts out its torque very low in the rpm range and thus the 3.42 would work better than 3.73 because the 3.73 will allow the engine to run out steam to quickly. But a modified car with cam, heads and exhaust will have a much higher power band to run in and the 3.73 gears can really shine.

 

I'd go no higher than 3.42 (3.45 if BW rear). 3.73's are too much for TBI and TPI motors.

Even the new Z06 Vettes with thier 6500 redline only have 3.42's and they seem to hit 11+ second runs with them.