87irocbeast

I have an 87 iroc z that came with a 305 tpi, 5 speed and 9 bolt borg warner 3.45s. Im trying to drop a 350 L98 tpi from a 91 trans am that had auto trans. I was going to just use the block and heads from the 350 and put my 305 sensors and use the same computer. I now know that I have to use the injecters, distributer est module, esc module, knock senser and eprom for a 350. Only problem is the 82-92s that had 350s in them only came with auto trans. So how can I use a 350 chip and keep my 5 speed? Help! Also I'm putting in a bigger cam. specs are (459 lift, 210 @ 050 duration and 212 lobe seperation. I'm trying to make 13s and stay smog legal. I live in nevada and have to pass smog. If the check engine light is on they wont pass it no how.

Tex95Z

Just cut the wires for the trans and tape them up. That is what I did, no codes at all.

Kevin91Z

What do you mean by cut the wires at the trans? The computer needs a signal from the speedometer or you will get a SES light for code 23.

You can try using the original chip, but to really do it right will require a custom chip. If you're ever in SoCal I can make you up a custom chip.

87irocbeast

I'm going to a shop that says they can make me a custom chip. But I'm not sure if I should use all the sensors from my old 305 or put 350 sensors (IE. est, esc, knock sensor)on it. They said to drive the car to them or tow it. Do you know if it will run with the 350 sensors on with the chip still being programed for the 305. I'm also going to put the 350 fuel injectors on. I think they are bigger than the 305 injectors. I know they can program for everything I just dont know if it will run to get it there.

87irocbeast

Another question: About what hp will i be at with my set up;91 L98 350 refreshed with new rings. Heads redone with 3 angle grind. cam @ 459 lift 270 dur. 210 @ 050 212 lobe seperation, tpi air foil, custom chip, and the 345 posi. It came stock in 91 @ 245 hp. I was hoping around 300 hp. I'm not looking for much more cus I've heard that my stock t5 tranny will break in half if I have too much.

Chevy86 IROC-Z

I would use the 305 heads on the 350 block. This will create more compression do to the fact the heads are slightly smaller in diameter since they are for a 305 block. More compression means more power.

87irocbeast

I thought of going with the the 305 heads too but my machine shop guy suggested that I stick with the 350 heads cus they flow better. the 350 heads are 194 x 160 and the 305 heads are 184 x150. He said the slight increase in compression wouldnt be worth giving up the better flow. Also he did something with the rings to give better compression.

Tex95Z

You will still need the wires for the VSS if applicable. However you do not need the square plug for the auto. I did mine that way (I used the vss though). I have never had any code for that, ever.

IROC-T

Problem with this is the 305's flow less air also,less air= less power.

Kevin91Z

Right, the square plug is for the torque converter lockup, its not needed for a manual trans.

Yes you can probably drive the 350 engine on the 305 chip. I did mine for a while with a 350 TPI and ZZ4 camshaft, until I learned to do my own chips.

IROC-T is right, 305 heads have smaller intake valves and they flow less air than comparable 350 heads. Always stick with 350 heads on 350 engines.

You can use all the sensors from your '87 engine on the '91 engine. They will all bolt up just fine. The '91 engine would be a speed density setup, and some sensors, such as the knock sensor, will not be compatible with your '87 computer.

thezisking

The 87 motor is a MAF setup. The 91 is not. Not sure how 87 computer will take to this.

BigBadLou

Correct, the '165 computer won't run the SD TPI setup.
I assumed when the OP said "dropping in a 91 L98 TPI 350", he meant with the harness and computer (as it's supposed to be done).
That way, the only nightmare in the swap is the wiring harness changes (thank you, GM!) and not the programming.

IIRC, the harnesses between the MAF and MAP TPI systems from '87 and '91 differ not only in the C207 pinout and C100 pinout but the wiper harness has been moved/changed drastically.
I don't have details but an engine swap search in Google or on TGO would help find them.

Lou

87irocbeast

Ok, to catch up on my swap. After trying combinations of sensors and wires. I went back to my original idea of just using the 350 block, heads,and fuel injectors. I kept the 305 computer, wiring harness and all 305 sensors. Its running great and no check engine light. No problems at all. I know that I will still need to get a 350 chip burned if I want to get all I can get out of the 350 but for now it lights up the tires and doesnt stop spinning til Im in 3rd. Very happy with it for now.

Kevin91Z

The '91 engine does not care what sensors are attached to it. They're almost all the same except the MAF and knock sensor, anyway. Use the '87 MAF setup and computer bolted to the '91 engine and all is good.