what's the difference between them?

 

the 305TPI is WAY better than a TBI, trust me i know from experience. The TBI is about the same thing as a V6 but you have the V8 sound. There is NO power coming from the TBI. Go with the TPI you can get A LOT more out of it. the TBI to the TPI.

 

what makes it so much better? (i'm car illiterate) .. i know they have the same cubic inches and everything, is it the heads ? or the tpi chip? or what?

 

The main thing is the induction. You get a lot more air in there through the TPI setup. Plus when you start modding it you can get the runners and all the extras on the TPI ported and get A LOT more horsepower out of it than you would with the crappy TBI.

 

alright. so the induction is the main difference.. i was looking through google looking for how big a difference (in hp) there was in tbi and tpi. the tpi had 205 hp (35 more than the tbi).. i'm just trying to get my car to beat this car that has a 5.0 tpi (it is stock).. any ideas on how i can beat him? and what's the cheapest way to get more horse?

 

My dad converted his 305 TBI to TPI, and gained 17 HP and 70 TQ at the rear wheels. He says the car has never felt better and the swap is very much worth it.

 

so basically, he just changed the tbi to a z28 motor... cool... how can you do it?

 

You will need to spend quite a few dollars on this conversion and it may not be worth it. Look into buying a 350 crate engine. More bang for your buck then a weak 305. My opinion.

 

I think the TPI motors typically also came with a more aggressive camshaft and better heads also. Generally the LB9s had the same cam as the l98. The roller with around .410 inches lift. I think the TBIs have flat tappet cams and the swirl port heads.

 

The 305TBI (LO3) has a smaller cam and crappy heads vs. the 305TPI (LB9). You can do the open element mod, add no more than a .460 lift cam to the LO3 (and a new chip burned), and you will have the 305TPI's begging for mercy.......or you can just converto to carb like I did and never look back!

JW

 

The tbi's also have smaller exhaost than the tpi. The heads were also different. Most of them had the same cam as the tbi. The tpi just makes tons more torque then the tbi.

If you are going to make the swap find a tpi car with the same trans and year to make the swap as easy as possible on you. Make sure you get everything. Computer, wireing harness, fuel pump, intake manifold, throttle cable and kickdown cable if you have an auto, and the air box. Your going to need gasgets and some fuel lines also.

 

The 5-speed tpis got a better cam than the tbi. TPI cars also had the luxury of posi traction, and 3.23 gears, along with an exhaust that wasnt 2.25" and didnt have the swirl port 187 heads. Basically everything that came stock on a 305 tbi motor is restrictive. I would have liked to pull some good times outa my car this year, but the lack of a posi rear and 2.73s along with stock tuning and a ****ty track didnt let me. But Im looking forward to next year. The only thing that kept me from doing the tpi route was the fact that it cost less to do heads/cam than to do the tpi swap.

 

posi was an option didnt come on all tpi cars

 

So were 3.23 gears, but the simple fact that you could get them was nice.

 

Yes they were options, TPI, Different gear ratios and Limited Slip to name a few. However; some of the original owner's did not buy these options. When I bought my IROC New in 1987 I had some financial limitations at the time. So some options were not considered which I am correcting to this day. Still glad I got the IROC.