I can not get a straight answer anywhere. i would like to know if it would be possible to swap out a 89rs 305 tbi with a GMPP zz4. if it is what would i need, would it be legal, and would it be worth it?, thanks guys so much for replying :hail: :hail: :hail: :hail:

 

It is a roller block so yes it will work. You will have to convert to a carb set-up but there is tons of stuff on how to do that. As for legality, depends on where you live. If you have visual inspection, no. If you have sniffer, maybe.

 

yes it is possible. i am in the process of doing the exact same thing. i am using a 650 barry grant demon carb. you will need all your accesories off your 305. starter, alt, ac if you want, and brackets. i am not using any somg stuff but i am sure you can.

you will also need an AFPR, or a new feul pump. tbi requires more pressure than a carb so an AFPR or a feul pump for a carb will fix that.

you could use your TBI or even go TPI but you will need a different cam for your ecm. this will also take power out of the zz4. when dynoed at 350 hp and 405 lbs it was with a carb.

as far as being street legal it comes with a sticker in the crate that says, not legal for use in california or any emissons controled vehicle after 1986. but there are ways around that. on top of that i have never ever had anyone that was inspecting my car look under my hood, or do a sniffer test, but that is in missouri.

 

Thanks so much Badbird and shifty, that helps alot, as for the emission testing i live in new york and they usally just do an exterior test. but if i have any other problems i know a mechanic , thanks again guys :hail:

 

What does being a roller block have to do with anything? One-piece rear main seal? Big deal.

You don't have to switch to carb. TBI can be made to work with the ZZ4. Go to the TBI forum for more info.

You're more likely to pass sniffer with TBI than you are with carb. Better gas mileage, torque converter lockup still works, etc.

Technically, it isn't legal anywhere within the United States. Practically, though, you won't have any problems getting it through inspection/testing.

 

With a zz4 you will get the most power out of it with a carb or multi port set-up. I don't even like carb but I think it is better than a TBI set-up for that motor. Guys can't even tune and supply enough air to a heads and cam 305 no less a 355 Hp screamer. Now a 4barrel tbi is a different story.

 

How to get the most power wasn't part of the question. Sure, you'd like to do that, but emissions (legality) and "worthwhileness" were the questions posed.

A stock TPI is a bigger restriction than what you can do with TBI. I do know a 3rd gen'r who did TPI on a ZZ3 (the same as a ZZ4), and the grand total of parts he retained from the orginal TPI setup were the fuel rails and ECM (but not the PROM). TBI would be almost the same with regard to parts replaced, but larger TB & injectors, better-flowing manifold, and PROM tuning would cost you a lot less than base, runners, plenum, TB, injectors, AND PROM tuning that TPI will require.

Going to carb because it's "simplier", or because it's cheaper, or makes more power cheaper, is setting yourself up for disaster at smog time.

The case against TBI is 100% related to the way the factory delivered it on showroom cars.

 

I agree and I should have taken TPI out of my Multi port comment. A zz4 is a lot of money to be restricting it. If smog is a concern and you don't need a 11 second car than a fully tuned TBi is not a problem. You will not need a zz4 under it though. A simple built up 350 with vortec heads will be cheaper and yield the same results.

 

Hey guys what about the 350 H.O. That cost about 2500 compared to the ZZ4 which is running about 3700 i am thinking that the first one will most likely be a better buy in which it only produces 25hp less in which i could just get a cam package or somethin along that line to get it up to that same mark, let me know what u think? i am a sponge for ur info, thanks guys! :hail: :hail: :hail: :hail:

 

the 350 Ho is a great buy. You can always switch cams. That is cheap compaired to heads and other things. However you may want to get the vortec heads machined to accept higher than a .480" lift cam. You could stull run an LT4 cam on that motor and you would have a really nice car. I say if you are going for TBI, I would skip the zz4 and go for the 350 HO. Unless you plan on making a serious motor where aluminum heads, Hyperutectic pistons and a balancing may be what you need.

 

What ET's would it be for the lo3 swap to the GM 350 HO with headers, catback 3.42 w/ posi?

 

It all boils down to how well you burn chips and dial in the tune. JProvost say high 12's with his 330HO TBI combo.

 

So if i buy a chip tuned for my engine, high 12's are possible?

 

Well anything is possible with enough money and chip burning patience. This not something you will get with one burn. You wil have to data log feverishly and burn and re burn new chips until you have it dialed in. It sound tedeous but it is not bad once you get the hang of it. Spend some time seaching on the DIY board to see if you are up to the task. Building a big inch TBI motor with all the proper goodies is not the hard part. Part throttle tuning, injector choices, FP, and WOT tuning are the things that make these swaps hard.

 

Mine passed as a 305 under the CA inspection. What they don't know won't hurt them