The Plan.......
I just bought a 350 vortec engine out of a 1998 GMC sierra. I have a 1987 Iroc Z camaro with a 305 TPI. I would like to swap out the 305 for the 350 vortec engine. My camaro is completely stock.

What I found out...........
I found a 350 Vortec TPI manifold that is supposed to work with a 350 vortec engine using the TPI setup by Edelbrock.

What i need to know.........
What lb. injectors am I going to have to use, What kind of distributor, MAF, ECM, Wiring harness, or what kind of main computer am I going to have to use.

Is this even possible or worth doing?

 

22 lb (350 size) injectors, 350 knock sensor, 350 PROM.

Nothing else "needs" to change.

It is very possible. It's probably worth doing. Slightly better than an L98 in terms of potential. The cam probably isn't optimal, but isn't necessarily "bad". You could do better, that's all.

 

Ok thank you. Now as far as cams go what would you use. I am planning to stroke and bore the 350 out. What cam would give me the most hp. Thanks.

 

as far as cams go, don't get something thats gonna peak out above 5000 RPM. The TPI will choke your air about 4800, depending on the setup. You could posibly go to 5300 with a stocker intake(no porting). If your going TPI, make sure your port that thing good. I'm going to swap out the TPI I have for a Holley stealth ram. Loads better on the top end.

 

If you go bigger, you're going to need serious TPI upgrades.

 

So What Mods would I have to do if i get a bigger cam? what about stroking? And why can't I have a bigger cam witout making any mods to the TPI system?

 

The TPI system was engineered for a 305. It does not flow well enough to supply air at Higher RPM's, which most "big" cams are made for. If you do decide to go TPI, you are going to have to port out the aftermarket runners and manifold to, maybe, get enough air flow to pull to 5500 RPM, maybe. Other alternative EFI system are availible. There is a forum on this site with lots of people posting info on Alternative systems.

 

What if i were to use the TPI system off of a 1987 IRoc with the 350 Would that work. I wasn't planning on using the 305 TPI system on the 350 vortec. I was going to buy the 350 TPI system, would this open up some air along with a K@n filter, After market runners along with the 350 TPI system?

 

Injector size, knock sensor, and PROM tuning are the only differences. None of those are the issue with the real problem holding back TPI with a bigger cam and displacement.

 

So then what is the issue of running a bigger cam?

 

the TPI system is the TPI system period. 305 or 350, same intake, same everything, except what the Moderator stated. The issue with running a bigger cam: is air flow at high rpm's. Do you know how a cam works???

 

Yes I know how a cam works. The cam opens and closes the valves. Depending on what the duration of the cam is controlls how long the valve is opened or closed. The lift determins how much the valve opens. I have never rebuilt a TPI engine before and with the other engines that I have rebuilt I have never had this problem, I don't have a lot of expereince with the TPI setup. Now what if i were to use a mild cam and port the crap out of the TPI intake? Would this allow me to have enough air flow?

 

What I am really confused about is why doesnt the MAF sensor need to be replaced? To me that would seem to be Reason because it measures the airflow. But I don't know its just a question. I am not real familiar with the TPI system I have only owned my camaro for about three months now and I'm also 16 and don't know everything that there is to know about the TPI.

 

Yes you can port the intake but only so much. Aftermarket intakes allow more flow out of the box, plus you can heavily port them also for more gains. The TPI system has long runner setup. It takes longer for the air to get from the valves than other setups. Carb's for instance. Air goes in at the top a hits the heads in no time, the TPI takes longer for this to happen. The TPI system produces large amounts of Low End Torque. This is the main purpose for TPI. Good low end power, but as soon as you rev past 4500 RPM with a stock intake , you are going to start choking the engine for air, and burning more fuel with not enough air, causing a rich mixture. Possibly a little black smoke. If your going to use a mild cam, and you're running a MAF sensor, you might not need a custom PROM burned. The advantage to the MAF sensor is it measures the air flow and sends info to the ECM, in turn sending timing adjustments and fuel mixtures for optimum performance. MAF's can also be modified, by removing the screen netting inside, or you can purchase aftermarket sensors that are larger.

 

That's not exactly what goes on or why it works or why modifications to it raise the RPM powerband. Think of the "tuned" part of "tuned port injection".

 

Ok, what about using one of these plenums along with slp intake runners from corvetteplenum.com I just bought one and I am wondering if this will work? Now Five7kid please explain the "tuned" part of TPI. Also if I don't cam all the mods that I need to do is Injectors 22lb 350 size, 350 prom, and a 350 knock sensor, what will I have to do if I decide to cam it?

 

If you change the cam, you need to modify the TPI to handle the extra RPMs and/or flow.

"Tuned port" means the length of the runner is tuned to provide maximum intake charge at a particular RPM. When the intake valve closes, the column of air that has been moving into the cylinder is suddenly stopped - this produces a pressure pulse that is reflected off of the closed intake valve and back up the intake track. When the pulse gets back up to the end of the runner at the plenum, a portion of the pressure is reflected back down the runner. The length of the runner and port is "tuned" so that it gets back to the intake valve just as the valve is opening. This pulse is a higher pressure, remember, so it pushes more air/fuel into the cylinder if it arrives when the valve is opening. The RPM at which the tuning is most effective is narrow and will change with air charge temperature - speed at which the pulse travels in the runner is determined by the density of the air in the runner, which is affected primarily by temperature, so that's why they have the coolant loop at the throttle body, to keep the air temperature more consistent. By cooling the intake charge temp, you increase the density and therefore the speed at which the pulse travels, so the RPM at which the pulse tuning is most effective will rise. Likewise, when you shorten the length of the runner, the RPM at which the tuning is most effective will rise (because it takes less time for the pulse to get back to the intake valve).

The stock TPI suffers not only with the RPM at which it is most effective (about 4800), but also by small diameter flow area. Aftermarket runners improve both, but will be most effective if the whole system is modified to increase flow (porting the plenum and base).

 

Ok thank you very much you cleared up alot for me, this is making a whole lot more sense.

Ok now I don't know if you have or haven't looked at the plenum that I bought off of corvetteplenum.com but if I were to use that Plenum along with SLP intake runners from which i understand are shorter and bigger than the stock runners along with the Edelbrock high flow TPI vortec baseplate would this make a bigger cam possible?

 

Shouldn't be a problem, but the cam will still need to be EFI-compatible.

 

Ok I don't know how to thank you all enough this has been very a informative and enjoyable experience! You sure do know what you are talking about (unlike others) and that makes me feel a lot better. Now only if the snow would melt in weld county I could drive my IROC. Now for another question where can I get a PROM and what kind of PROM do I need? Can I just take one out of a 87' IROC with a 350 or what?

 

the PROM depends on a few things. Are you going to a huge cam or not? Larger injectors?? If you modifiy too many things you will need a custom tuned PROM. You can use a stock '87 350 Prom if you are running mild. You may notice a few "funny" spots (like a stutter or miss) on your tach if you have a incorrect PROM tune.

 

Ok what my plans are is to run a mild cam and I don't plan on changing the injectors as far as the poundage. But changing to the 350 size, is there even a difference btwn 305 and 350 injectors. If I do all of that will I need to get a "burned" PROM or can I use the PROM out of the other Iroc? Also is there an upgraded chip that I can use to bring up the HP or not? If so what kind of chip would I have to get? Thanks.

 

ok here goes : you can run a mild cam, but you may notice a stutter in your rhythm somewhere if you use a stock PROM.

A "PROM" is Programmable Read Only Memory. This is the chip that runs your ECM, that makes your car go.

There are stock versions but they differ between 305's and 350's, the injectors also differ between 305's and 350's. The poundage differs, to run a mild cam with a 350 you will want at least 22# injectors(stock 350 injector size)