Hey! I am about to purshase an 86 Iroc wich has a 5.o TBI. The engine is running great but I intend to bring some upgrades to it.
My concerns are :Is it worthed to remain with the TBI system over a TPI(wich I have as spare)?? Basically, I would rebuilt the engine and add a bigger cam, roller rockers, L98 heads aluminum, and a complete exhaust... Since I already have two complete TPI settup (MAF and MAP) I am considering this option...

I never built a TBI engine and wonder the real HP/Torque potential? Any suggestions...

Thanks, Pat

 

EDIT: damn! Didnt see your sig Wouldve been telling you stuff you already know

 

If you want to use the tbi Id get a 454 tbi, 80 pph injectors, good single plane carb intake, adapter, and high flow fuel pump. If you dont have prom burning equipment youll need that. Id get the PP2 or the flash and burn, G2 adapter from moates.net, and some flash rom. After that youll want to get an editor. The DIY-Prom board has many threads on this so do a search. All in all id keep the powerband under 5500 rpm and the LSA at 112 or more to ensure you can both feed it and stay within the limits of the tbi ecm. Properly tuned it should eb able to support what you wish to run. The only possible problem may be idling as the pulsewitdths will get really short, but with a VacAFPR you can sort of get around this.

 

That is completely up to you. I changed from 350 TBI to 350 TPI because I never really liked the fuel system enough to put money into it when I didnt have to. I noticed the TPI made a incredible amount more midrange than the TBI could dream of. I drove my employee's 305 TPI TA and it felt balanced, but it didnt have the throw you in the back torque my 350 has.

Take that for what its worth.

 

TPI (stock) = long intake runners = lots of low and mid range. Carb/TBI = short runners = lots of mid and high range. The only difference between carb and TBI is that carbs are easier to tune. The advantage of TBI over carb is the reliability that it'll idle for a year if you had a big enough gas tank . Compensations let the TBI control the AFR better than any carb on the market so that's the only REAL advantage.
Keep this in mind; stock TBI calibrations were for anymic engines with the bottom of the barrel parts. This is why TBI runs like **** with a stock tune. Without tuning (speed density) it'll only supply enough fuel to make x amount of horsepower. Hence the bad rap given to TBI through countless magazine articles written by non-engineers. Any calibrations engineer will tell you that it's possible to make x amount of horsepower with x amount of air and x amount of fuel. If you don't give it enough fuel (stock TBI injectors and fuel pressure) you aren't going to make diddly squat worth of horsepower. Make sence?

 

I knew this....

 

Is there some reason you are not
considering a carb?

 

Hey thanks for all your clues!

Actually, I was thinking in a carburator combo but then, I would have to buy stuff: intake/carb/air element etc. Since I already have a COMPLETE speed density (with SLP runners & Edelbrock base) and Maf setup, I would prefer to spend the extra money in good heads/porting. As for the engine, it is a TBI and functionnal/reliable but STOCK!

As for fuel efficiency, it does concern me but only to a certain point. I would like to stick with the 305 or my 5.0TPI and just refresh it with good components.

This will be a daily driven vehicule so I do need fuel reliability and a good launch when needed. The car is auto so I will probably go with a 3.23 ratio/stock converter.

Thanks again for sharing

 

Hey 91z28ss, check your pm