arite here it goes. i have a 1990 RS and jsut finished swapping out a 305 TBI and put in a built 355. i kept my 305 intake and TBI set up on this 355 just for money reasons for now and of course the power is good but its not the best. i've been reading a lott of posts about tbi and tpi, and also read up on MPFI. i want to switch to another kind of fuel injection without having to change everything over to carb just because i like the better fuel economy. i mean 15 mpg is better that 14 mpg right haha. but what way should i go for the EFI swap because any way i go i'll be needing the entire system from the computer all the way to the new sensors. Money is an option but i'm a guy who'll save up for the best of whatever so should i go with a TPI conversion or an MPFI conversion and any suggestions on brands and where to find it is always apreciated or i could go to a junk yard but new is deffinitely better. later on i deffinitey want to supercharge the engine so i'm leaning toward TPI but i just need a little guidence.

 

TPI is just a form of MPFI. Same thing. MPFI stands for "multiport fuel injection". TPI is "tuned port injection".

Here's two great swapping guides for you to read up on.

https://www.thirdgen.org/newdesign/tech/tbitotpi.shtml

http://sethirdgen.org/tpi1.htm

Money is everything. There are aftermarket options to get MPFI. These can cost $2000-3000 though. Staying GM will keep parts prices low. Still look at at least 1/2 of aftermarket prices.

 

thanx a lot for the help i really appreciate it. I did know that TPI is a form of MPFI and i knew about what all the letters meant but i was talking about an MPFI unit like edelbrock makes where there are fuel rails set up onto the intake manifold and the top looks like a throttlebody or a carb where the TPi unit has runners and all of that other good stuff. But thanks a lot for the help

 

So what's your question?

 

my question is which system would i benefit more from as far as expanding to a supercharger and buying better heads or jsut which system is better all around: the TPI like in third gen 350's or the aftermarket MPFI like edelbrock offers

 

Typically the TPI intake is an rpm killer, it doesn't flow enough to make HP over 4500 rpm. There are supercharger kits available for the TPI unlike the Edlebrock MPFI which has no aftermarket direct fit supercharger.

Supercharging changes the rules though, since you're pressurizing the intake charge you don't have those restrictions anymore.

There are other "TPI style" intakes out there that accept a near direct fit aftermarket supercharger. Here's a great webpage comparing these other intakes.

http://www.stealthram.com/intakecompare.html

I'm partial to the LT1 intake conversion. It can use the supercharger that sells for the TPI systems with very little modifications.

 

that's another question i had but idk if it has anything to do with TPI it prolly doesn't but is there a way to convert my 355 sbc with the 305 intake manifold, tbi, and 305 ECM to an LT1 or LS1 style cause isn't the only difference between the 3 engines (355 TBI, LT1, and LS1) the top part of the engine meaning from the intake manifold up?

 

Yes, you CAN convert your TBI intake to a TPI, LT1, HSR, Superram, ect....by using the link I gave you in my first post.

https://www.thirdgen.org/newdesign/tech/tbitotpi.shtml

That would be for TPI but you can use it as a guide to convert to the other types of EFI intakes.

Forget about the LS1, it is a TOTALLY different engine. There is nothing that crosses to our regular gen 1 SBC. The LS1 is a gen 3 engine.
Take that back, you can swap connecting rods between all 3 gen SBC's.

The LT1 is a gen 2 engine. The intake can cross to a gen 1 SBC like you have with some modifications.

 

well i think i may just do an LT1 conversion instead of a 3rd gen TPI conversion and thanks for that site btw, i read through it and it helped me with this decision.