305 TBI to 350 TBI - Third Generation F-Body Message Boards

weberflorida · 05-18-2003, 01:34 PM

Hey guys I am pretty new to this board so sorry about the dumb questions. I have a 91 RS with a 305 TBI motor. I am wanting to put in a 350 long block out of a 91 Z. I will I be able to just keep all the same injection stuff and just swap the longblocks? I know that I will need a new knock sensor and maybe larger injectors but will I need anything else. Thanks guys

87WS6 · 05-18-2003, 04:57 PM

You can do it. Personally I wouldn't keep the TBI setup. I think it would keep you from realizing the full potential of your engine.

Depending on the laws in your state I would rip out that TBI setup and go carb. TPI will be a bit restrictive for a 350 also.

I prefer fuel injection. An aftermarket DFI is the way to go.

weberflorida · 05-18-2003, 05:19 PM

Thanks for the info. I will look into some after market fuel injection systems. Why is the TBI so restrictive?

Deemax · 05-19-2003, 07:59 AM

You gotta weigh the cost vs. benefit. If you have the TBI now, its a real simple, and obviously inexpensive, swap. Everything bolts in, all you need to change is the knock sensor, injectors, and chip to accomadate the 350. Sure, you can make more power from a factory TPI or aftermarket FI system...but it'll cost ya. I was looking for around 300HP from my 350. I got there using the old 305's TBI. It all depends on how much power you want, and how much you're willing to spend.

weberflorida · 05-21-2003, 06:54 PM

Thanks for giving info. Gives me a little more to think about. I will get back to you on specifics if I decide to go radical. Thanks again.

Mark1963 · 05-22-2003, 11:14 PM

You were asking why the TBI is restrictive. The main reasons are intake and exhaust. You could use a carb intake manifold with an adaptor plate, a holley 670 TBI unit and a better air box will help with fuel and air delivery. Some decent headers and exhaust will help.
I'm replacing my 305 TBI with a 355 engine with the holley TBi unit.

weberflorida · 05-23-2003, 05:26 PM

What kind of horsepower do you think you will make with that motor? Does anybody know what kind of horsepower and torque you can get out of a tbi motor?

Thanks

vwdave · 05-23-2003, 07:32 PM

In florida, all the emmisions stuff is fair game. I completely removed mine. Helped alot in power.

Weber, I am guessing about 240-275hp and 300lb-ft at the wheels.

Mark1963 · 05-23-2003, 08:08 PM

I've got an edelbrock performer rpm setup. Estimated hp for this engine is up to 420. Will have to wait to see whether the tbi restricts the engine, looking at other posts, people have got up to 400hp using tbi.

Mark

weberflorida · 05-23-2003, 08:18 PM

Guys thanks for the posts. I think I am going to try it stock TBI with 350 injectors and a different maniflold. See how that works first. Thanks again.