i just registered, and i assume this question has been asked like a billion times on these boards, so sorry in advance. i own a 91 RS with a 305 TBI of course, and am going to for sure ditch the LO3 and 700R4 in about 1-2 years, when i get enough money, and replace it with an LS1 (or LS6 if i get lucky and find one from a wrecked Z06) and a matching manual tranny. i know this is gonna bit more than a little pricey, which is why it's not happening any time soon. however, until then, i'm stuck with an LO3, and nothing against TBI fans, but quite frankly i hate this motor. 170 hp/225lb-ft is horrible for a 5 litre chevy V8. the car came with a K/N intake, and flowmaster 80's, which helps somewhat. anyways, i've considered getting a used 305 TPI setup from either eBay or a junkyard. will this swap cleanly without having to do significant mods? how much will this cost (parts)? also, what type of power gain can expect from swapping the TPI on? and lastly, the main reason i'm getting the LS1/LS6 is the 28-30 MPG it gets. however, the 350 HP the LS1 puts out is pretty appealing too. could i possibly get this out of a 305 TPI without running ridiculous psi's and compromising my gas mileage? and would the price involved be practical, or should i just save my money for the LS1? thanks for the help.

 

You are correct on this question being covered many times, if you run a search you will get many replys to this same query. But as to your question of getting 350ish Hp and 28-30MPG from a TPI, your better off saving your money for the LS1, I don't believe it is even possible to produce both of those numbers w/ a TPI w/ any tranny imagined. To produce judicious power is to compromise MPG in most cases. It takes air and FUEL to make power. Fuel Injected engines have come a long way since the TPI. So far in fact as to produce 405hp/29mpg (don't quote %100) in the ZO6 vettes. Amazing. But that is just my opinion.

 

Welcome to the board!
The TPI will give you more torque at mid-RPMs.
Not sure exactly how much with a 305 TBI eng.
The TBI heads and cam will hold you back some.

To swap you will need to replace the fuel pump, ECM, harness, and tranny TV cable along with the obvious intake parts.

The easiest way is to buy a wrecked 350 TPI car and swap everything over.

If you're willing to dabble in EPROM tuning, you can get fairly close to the 28 MPG mark. The later bins ($6E) have "highway mode" which will help your highway mileage. I've yet to enable it on my car since I'm still tweaking my ign timing.

My combo gets abt 20 MPG city/highway avg. It would do better if I could keep my foot out of it.

 

if you are intrested, i have a complete TPI unit off of my 87 IROC, i replaced it with the HSR, i have no use for it anymore and i'm willing to get rid of it at a good price for everything that you need except the wiring harness. I have a TPIS ported plendum, TPIS fuel pressure regulator, throttle body, fuel injectors, runners, fuel rails, well i have everything that you need, if you or anyone else is intrested please let me know and i will give all details about it!!!

 

That's what I did
http://www.cardomain.com/memberpage/400090/5

It will give you gobs of torque. I've read upwards of 70lb/ft just by swapping intakes. FYI, the LO3 cam is the second smallest cam GM ever put in a car. While the intake is off, I'd put in a new cam.

Heads-Even if you could find some 305 TPI heads, that'd help tremendously. The LO3 Swirl Port design kill the 305 after 3000 rpm. If you can't afford new heads, I'd at least try to P/P the stock heads as much as you can. Good luck, let me know how the swap goes, I'll be tackling it next winter!

-Corey

 

YO!!!! I WANT IT!!!, im tired of my 5.slow with TPI ill produce this

 

If you are really intrested in purchasing that please e mail me at irocing@yahoo.com and we can talk about it!