I'm looking at a '89 RS 305 TBI and was wondering what kind of mods can make the best power, and how reliable the TBI system is. Would it be better to turn it into a EFI or TPI, or mod the motor as a TBI?
Also, how hard is it to convert it to carb.

 

My experience has always been that TBI is the happy medium between the reliability and ease of maintenance of a carburetor and the performance of more electric fuel injection systems.

As far as I know, the best way to get a whole lot more power would be going with a different system. A intake/header/cam/carburetor setup is a reliable way to go if you've got the cash and the savvy.

IIRC, You can add nitrous oxide systems to TBI via a riser between the unit and the intake manifold. Or just a header/intake/cam setup will free up some ponies.

As far as stock, i think the verdict is that TPI is the top HP producer. couple it with a 5-speed, and that should be the quickest stock third gen on the road. TPI's require complex electrical systems, though. I'm a bit more mechanically inclined than electrically, so I tend to lean in the carburetor/TBI direction.

A 305 with a TBI unit is no kick in the crotch, though.

As far as retrofitting a carburetor, shouldn't be too difficult. The systems run similarly. At worst, you'd need a new intake manifold, riser and fuel pump. If you have the means to terminate fuel lines, that would help also, but likely wont be necessary. The hardest part, then, will be removing the sensors that the ECM uses to determine how the TBI unit operates.

Good luck with your selection.

 

This question is asked more than once a week - read through the threads on the TBI forum and search - there's a gazillion threads on TBI mods.

In the end, none are good for much. The TBI computer is just too restrictive. Best bang for the buck is to save up for a 350 swap, and use a 350 TBI chip, injectors, and knock sensor from a truck or Caprice.