i've been looking for a firebird, and i found an awesome '89 formula .... with one exception.

i was looking for a tpi setup. this one has a 305 tbi 5spd with a 3:08 open rear. i'm looking to see what i can get out of the 305 with bolt-on upgrades, then considering a switch to a 350, 383 or 400 if/when the 305 lets go.

i'm wondering what the positives and negatives are when comparing tbi to tpi. how tunable is it, what are the upper horsepower limits of the system. if tpi is significantly better than tbi, is a swap to tpi reasonably feasable? what changes other than the actual fuel injection units would be necessary? i've read that tbi has better low and mid-range torque than tpi, whis is attractive to me. is this true?

this car is in awesome shape and is exactly what i've been looking for, with that one exception. stay, or walk away?

 

Do a search. This subject has been covered before and usually ends up as a pretty heated debate.

 

the general consensious is that the two systems have nearly identical power bands, i.e. neither is good for high rpm use. Id say both stock tbi and tpi systems are good for street use in daily drivers. Tpi tends to give better torque output then tbi due to the long intake runners. The main difference is thata the tbi engines have crappy heads, poor stock intake, and the tuning in the tbi computer sucks in stock form. Both will need various bolt on parts such as headers and exaust to get some decent power and in the case of the tbi, in addn. to that, youll have to ditch the stock cam, heads, intake, stock 1200 stall torque converter, and buy prom burning equipment to get it out of the 16's. Id shoot for the L98 (350 tpi). Your getting better heads and more cubes to start off with so youll be further up the hill then youd be with the tbi. If the formula is in good shape, id say its worth it if you want a daily driver but beware, itll take some time and research to determine what mods will work best for you.

 

oh, almost forgot, the stock BW manual T5 is tin foil. Youll need a t56 or a tremmec 3550 if you want a maunual trans to last behind a modded setup. and, DONT GET T-TOPS!!! THEY SUCK!!!!!

 

Yeah t5s are junk. And I also hate my t-tops. I rarely take them off, makes the sun fry you, cars not as rigid, t top cars are heaviers....man I wish I had a hardtop.

 

I dont know about anyone else besides you two, but I LOVE my t-tops. Some leak, yes, but its very fixable, and as for the flex problems, some SFC's should take care of that, I would think. They may suck for drag strips, but I'll tell you what, I'd never trade in my t-tops for summer driving! Plus they just look plane sexy! Hehe. Anyways, guess everyone has their opinion, and thats mine.

Later,
Ben

 

i too love the t-tops.

since ALL thirdgens have wet noodle uni-bodies, they ALL need SFC's so that equals things out.

as for weight.

CC1 T-Tops 29.5

so t-tops add 30lbs, do an !AC, since you don't really need it, since the roof is removable, and you have lost way more than the wieght of the t's

 

Very much agreed! Well worth the weight IMO anyways. But I also forgot to mention that all F-body's could use the SFC's anyways regardless of t-tops or hardtops. Good points, Dewey. Again, all a matter of optinion and likes/dislikes tho, anyways, if you like the car, id say get it. Think you will be happy with it. You gotta love Formula's, and its a standard tranny to boot, even better!

 

So you're saying that you don't need A/C because the roof is removable? I don't know about you, but my IROC vert didn't have A/C and I just about died in the hot summer days even when my top was down. When I bought the car I thought the same thing: hey I don't care that this car wasnt optioned with A/C; the top comes down and that will keep me cool! I was so wrong....

 

if your going to go the t-top route, get SFC's. I didnt and all the flex really loosened up the t-tops. Although they where fine when i got the car, they leak like mad now. As for a/c, i dont have it and i dont miss it, either. But, of coarse, my metabolism is virtually non-exsistant so the heat usually doesnt bother me.

 

ackkkkkkk! how did my tbi post turn into a t-top post?

btw ..... i had an 87 firebird that i loved, and one of the things i loved most about it was the t-tops. all you have to do is make sure the windows and t-tops are adjusted properly and the seals are lubed and they don't leak. i had my 87 for 9 years with no problems (except at a high-pressure car wash!).

i just bought the '89. it already has subframe connectors, although they're bolted in, not welded. it also has a cat back 2 1/2" exhaust with a flowmaster, b&m ripper shifter, msd coil, aftermarket rear lower control arms and adjustable panhard bar. paint's in great shape and interior is amazing. paid 3,500 ... a little high, but not when you factor in all the aftermarket pieces included, how well maintained it is and the low mileage (90k)

which brings me back to the original question.

i plan to try and tweak the 305 a bit before upgrading the engine. i'll put headers, cam heads, etc on the engine, but will only do mods that will translate to a 350 or 383. this will be a daily driver, i'm not going to go crazy.

from reading the postings on here, i've come to suspect the tbi can be made to work. i like the idea of computer control and the improved fuel economy available with fuel injection.

 

In my opinion, it's hardly something to base buying a car on unless you're just looking for something to drive. If you (as I suspect) also want to mod or work on the vehicle, it's not that big a deal. Especially if you see a motor swap in the near future anyway. As far as the work to swap, besides what you end up doing in the engine bay, there's some minor wiring inside the car, and a fuel pump swap involved.

On the other hand, if you're like a lot of other people here, who dream and dream and dream, then hit one little curve and decide to sell the car because it's too hard to get where they want it.. take a pass and just get what you're looking for right off the bat.

A completely untouched TPI will outperform a mildly modified TBI after second gear. But for the first 60' that TBI sure is torquey.

You can't beat TBI for reliability and cheap replacement parts, though.

 

All i can say is that buying the 305 LO3 TBI was one of the worst decisions i have ever made....

Be careful and take in other things to consider...

Check the tech articles on the main page to see what the work is to switch to a TPI

 

I own both a 305 TPI and a 305 TBI, both are 5 speeds. Stock for stock the TPI will win in probably every catagory except intial price. (~50 hp more stock and much better(stiffer) suspension, better gears and posi traction). However, I think the TBI is cheaper to mod(ex. intake manifold for TBI ~$50-200, vs. TPI full intake manifold is $300-500+ or more SR) assuming you like to do your own work.

Just saw your new post, not sure what your ET goals are, but with a bigger engine if you want better than say high 12s, then I doubt you'll be able to swap very much from the 305 to a bigger engine. Exhaust is the first thing that comes to mind and I wouldn't go bigger than 1 5/8" on headers and single 3 ", but that would probably barely due(not desired) on aftermarket headed 350 or 383. Same with heads and cam. Too big for one or too mild for the other.

ex. I was running a 214/220 cam in my 305 TPI which was ok for a daily driver, but it sometimes had hard brake pedal and no power until 1500-2000 rpm, and that's a mild cam for a 350 or 383. And it still only ran low 14s.

I'd say you can get(average) mid to high 14s in a 5 speed 305 TBI with gears, cam, and bolt ons, which is about the same as a 305 TPI(maybe high 13s to mid 14s)

After sunday (1/19) I'll report a new time hopefully high 14s on a stock long block LO3 as I just finished a header install last night and what a difference.

 

i dont regret buying my tbi. Granted its not super fast and would only pull mid 14's if i got lucky but it sure is easy to work on. The parts are dirt cheap, its simple, and its dead reliable. What i do regret is buying a bright red car and then putting a loud exaust on it. Seems like everyone wants a piece of my car. Always have some ***** flashing his blue head lights at me trying to start someone. Ive even had an old lady wearing a mink coat pull up next to me in a caddy with a northstar wanting to race. She started revving the engine and shot fire at me with her eyes while angrily pointing her finger straight ahead. I didnt race her, too buisy LMAO. Gotta admit that the caddy did launch nice, though.

 

teh battle of teh induction systems has no place on these boards. carb, tbi and tpi all have their good and bad points. all have been reworked into making respectable power.
that is the end of this thread.

later
tim