need some tbi help

[munroe]

im swithching the caebed 350 that was sawppep into my 87 for a tbi 350. it origionally came with a tbi 305. what i need to know is what computer would be the best one to use. fortunaly the wiring harness is still there. the other thing i was wondering is, is there any advantage to sswitching from a tbi to a tpi manifold?

[Jim85IROC]

The computer that you have already will work. You will need the PROM from a TBI 350 truck though. You'll also need the larger injectors, the correct knock sensor, and perhaps 1 or 2 other small widgets.

As for TPI vs. TBI, the difference is huge. You can't just change the intake manifold. You need the entire induction system, wiring harness, computer, as well as fuel system modifications (fuel pump, lines, etc). However, TPI is a major step in the right direction over TBI. TBI is fine for a stock motor, but is virtually worthless if you want to do any kind of modifications. TPI in stock form can be a bit restrictive on a healthy small block, but will make excellent torque, and has a very large aftermarket that will allow you to mod to your heart's content.

[munroe]

if i only need the eprom itll be cheaper than a computer, and i might be able to get the guys in siga platoon to put it in for me.
does anyone have a list of parts ill need for a tpi swap. ive got the engine on a stand in the eme platoons shop, so now would be the time to do the swap if its not too expensive

[Russell]

I'd suggest getting it running with the TBI setup first -- Then start researching your TPI swap. Don't be hasty in starting an under-taking like that, I did, and it held my truck up at least a year before I bailed on it due to various problems that could have been avoided if I did my research a bit better

[munroe]

good advice. since the wiring harness for the tbi is still there, and im assuming the electrical fuel pump is still in the tank, it might be the best idea. the eprom ill need, can i buy and aftermarket on instead of replacing the 305 one with a stock 350 eprom?

[Jim85IROC]

I have to disagree to an extent. It's always nice to get it running good first, but if the motor already runs well in the current truck, you already know that the long block is ok. I'd do the TPI upgrade while you've got everything apart.

Your best bet for doing a TPI upgrade is to buy a complete TPI setup. Stay away from one off an 85 because their primitive computer sucks. Anything from an 86-92 will work fine. I'd suggest an 86-89 if you intend to keep the vehicle relatively stock and under 350-ish horsepower. The 86-89 uses a mass air sensor and does a better job of adjusting to engine changes, but really is only effective up to about 350 horse. The 90-92 systems used speed density, and are more sensitive to changes to the point where you'd really be best off with a custom chip after every semi-major upgrade.

So, in terms of what you'll need:

TPI intake including baseplate, runners, plenum, throttle body, and intake piece between the MAF and the throttle body.

Harness complete with relays

ECM

Appropriate chip (plan on having a custom one burned for your application)

Injectors (305s came with 19lb/hr injectors, 350s came with 22s. If you have a custom chip burned, you can get away with either on a stock TBI 350 motor)

Fuel rails & fuel pressure regulator

Sensors (mass airflow or MAP, air temp sensor, oxygen sensor, etc). Most of these are already on your TBI motor.

Throttle cable

TV cable for the transmission

High pressure fuel pump (Walbro 255lb/hr is a popular choice)

That may not be a 100% list, but it gives you an idea. It sounds like a lot, but most of the time when you buy a full set on Ebay, it'll include all of that except for the last 3 things, which are easy to get, and of course the custom chip. If you're serious about doing the swap, I'd pick up a couple books. One is the "TPI Swapper's Guide" and the other one is "How to Tune And Modify Tuned Port Injection". Both are very good references, especially the first one. It'll give you a good education of how TPI works, and once you figure that out, you'll have a good understanding of how to put it together from a system-level standpoint.

[Captkaos]

I would avoid the '85 version just the computer, which can be replaced with either a MAP or MAF system.

For the quickest method, pull the intake off a know running motor and take everything. The 85-91 Vette and 85-86 F-body intake will actually bolt to all pre-87 blocks with no modifications. The 89-up didn't have the 9th injector.

Found the site that list EVERYTHING... http://hotrodlane.cc/PDFFILES/TPIStory.pdf

Street and Performance also had an "integrator" harness that will work with the existing TBI harness, http://www.hotrodlane.cc/ONLINETECH/intergrator.html unless you completely convert.

In my honest opinion, if you are not going to get it off a running motor, break down and buy the whole system, you will come out cheaper and spend less time looking for parts.

[Russell]

If you've got all the TBI stuff there right now, and all you need to do is swap the PROM out with a 350 version, then you have your truck up and running, ready to go right now. TPI does offer slightly better performance as far as torque goes, but I am not entirely sure it is worth the expense to make the swap. Makes a great conversation piece, but really, the performance on a 350 is hardly worth writing home about.

Try the TBI 350 and see how you like it. The TPI will rev faster and doesn't suffer from some of the possible atomization problems that a wet intake design can under certain conditions, but overall, they are pretty similar.

If you've got your heart set on TPI, it would only take an afternoon to make the swap once you've got all your ducks in a row. Its easy for guys who have completed the swap to tell you to just jump in and do it, but you can save yourself a lot of time, money, and frustration if you know exactly what you're gonna do before you do it.

As mentioned above, I would very highly recommend that you get a complete running donor engine to pick parts off of. I personally made all the mistakes a guy can make when starting one of these swaps, I got myself an 85 Camaro setup from a 305, and bought it off ebay incomplete. I wound up spending a lot more money tracking down new parts to replace peices that were missing, or not working.

I also had to replace the injectors, ECM, do a bunch of re-wiring and purchase a new PROM for a 350 before I could even consider firing my engine up. Once I did get it fired up, I was plagued with problems because my engine wasn't built properly for an EFI system.

Again, I'm not telling you not to do the swap, but I am telling you to do some reading first, see what problems other's have come across, see how those problems were solved, and know exactly what you are buying before you spend a dime on it. Make sure it is really what you want, and not just a whim thing cause it looks so cool

[munroe]

i think ill throw the tbi in for now as it wont cost me much more to get it in the truck, and think about tpi or a ram jet or somthing later on