I have a 87 iroc z that came with the 305 tpi and t5 tranny. I bought it for 650 bucks. The 305 had a loud clapping noise that I found out was a piston with the skirts broken off. May have been caused by not having a knock sensor hooked up. Anyway Im got a 350 tpi from a junk yard and had it rebuilt. My question is will my original computer be compatible with the knock sensor from the 350? The knock sensors are different mainly because in 1990 the 350s used lighter pistons made from a different metel. I guess they make a different pinging sound. Also if anyone has done this swap before, what other problems will I get? Thanx for any tips and help.

I just swaped 87 TPI onto an 89. And let me tell you many changes where made from 87 to 88 then a whole lot more changes where made from 89 to 90. To start with are youg going to be useing the wiring harness from the 87 on your 90? if so you will spend most of your time changing wires in your wiring harness. some of the things that changed from 87 to 88 was:

How the fuel pump wire runs to the fuel pump
how the alternator wires(more then one) are ran
how the fuel pump rely was wired
how the injecter 12v wires was ran
the 12v MAF wire was ran
alternator and A/C compresser where swap from right to left(V-belts to Serptentine)
Windsheild wipers are diffrent
windsheild wash is diffrent
all A/C wires are diffrent
NO VATs in 87
also the 86 and 87 have a two part wiring harness and the 88 and up has one sold wiring harness.
9th injector on 88 and older TPI
and a few other things that i can't remember right now.

All the bolting up stuff is just about the same but in order to tell you more i would have to know what it is that you are doing. And what parts you have.

well for starters the knock sensors never swap over from a 305 to a 350, different setups, your best bet instead of hacking and splicing wires would be to just find a harness from that year, OR if youre good with a soldering iron, have a blast ive gotta tear my "new" harness apart for my TPI conversion and so far its a nightmare

also you need to see if its MAF or MAP, depending on what youre already running youll probably run into an issue there, say youre running the MAP which is speed density, and youre new 350 runs MAF (which i believe was a big changeover that year) A. You need to get the wiring done to run it, B. youre computer is gonna have to be swapped out so it knows whats going on, the only thing that computer knows how to do is recieve sensor input, and send out a signal for fuel metering.

Best bet like i said is go get the new harness and probably a new ECM well, not new, but the proper one.

Good luck

Actually all im doing is using the block, fuel injectors and heads from the 91 350. everything else is going to be in my 87 iroc. Im going to use the 91 350 knock sensor cuz the 350 has pistons made from a different metal.

Rip it all out and carb it. Carb.>TPI. Simplicity keeps you driving. Complication keeps you thinking. Good luck either way.

Well if you have an 87 Iroc with 305 TPI and you wish to replace your 305 with a 350 all you will need is a 350 Long block 24Lb Injectors and a new prom. should be pretty easy, other then that it's not diffrent then pulling out whats allready there and putting in an other 305 TPI.

Thanx for the info guys. I'm hoping to fire it up on thursday. It will probably be running rich since the injectors are bigger. So I will take it down to a computer
shop and have them program my chip for the bigger injectors and different knock sensor. They said they would do it for 115 bucks. Im anxous and a little nervous. I hope she fires up and runs good enough to get me to the shop.

After I get every thing done and running right I'm hoping to be able to run in the high 13s. The only mods i did to the motor is a bigger cam (459 lift 210 duration @ .50 and 212 lobe seperation)tpi air foil, and free flow cat. my machine shop guy did something with the piston rings to bump up my compression to around 10.0 to1. And also a valve job with 3 angle grind. I wanted to port the intake and runners but i dont know how to do it. What ya think, high 13s possible?

High 13's are possible with that setup if your T5 doesn't break. That cam is not much bigger than stock but it will make enough torque to cause traction problems with stock suspension. And with the T5, wheelspin is probably a good thing. My '91 350/auto went 14.2@98mph completely stock with 117K miles, but it weighs a few hundred pounds less than your car. Remember, no powershifting!!

I have a questionn related to this topic, the orginal owner took off all the fuel injecter plugs for some strange reason. How do I know which plugs go on which injecter. Also i have after market injecters I just installed.

it's single batch fire. They don't have to be in order.

I have tpi dont they have to be in the firing order?

Port injection doesn't necessarily mean sequential.

They're batch fire (all 8 at once.) Not 4 then 4.

Trace the wiring to and into the ECM to the injector driver. Nothing will make the injectors fire separately.

That makes no sense at all, how is the engine suppost to run if all 8 injecters fire at once,they have to go in the firing order at the right timing shooting aall them at once will do nothing but just leave fuel sitting in the valve.

Like a carborator*

http://www.ehow.com/about_5398218_tu...injection.html

Im not trying to start an argument in all honesty it would be easier for me if the plugs didnt matter what injecter they would be on(batch fire) but every other person has somthing to say and i dont want to have a miss fire if they are in fact individual injection.

Thank you for your help jmd

If you want to verify this on a running car, you could hook up 2 noid lights and see that any two injectors are fired at the same time.

You're right. A carburetor's air/fuel mixture hits the intake valve as it's closed too. Things go into the cylinder just fine with a carb. Just not perfect. It's a pretty small difference to have sequential-fired injectors. The 93 (batch) and 94 (sequential) LT1s were rated the same power.

all lengths of my fuel injecter wires are differnt, 4 fuel injecters have the same wire color and the other four have differnt wires. With that information does that prove or disprove the batch theory?

Plus the longest part of the harness is going to go to the farthest injector, so on and so forth

Neither.

You can go by the info here to wire yours:
http://www.diy-efi.org/gmecm/ecm_info/1227165/

Which at least tells you the light green is for 2,4,6,8.

The two wires at the ECM connectors are separate. The single injector driver inside is what makes it batch, not bank.

Edit: that is for the 86-89 ECM. The `730 ECM stuff shows dark green for 2,4,6,8