Hey lads,
I need as much help and info on the parts needed and ECM mods to do a swap in my 86 IROC Z, the 305 just died and i want to put in a full roller 350 with same TPI on it. where do i start? I also need to know if the ECM will know if I put a different dissy in it, the crappy 86 TPI dissy is hard to get and costs a fortune. Any help will be much appreciated.
Nick

 

Alright, first off is the car MAF or Speed Density? The same dizzy will work, but any small cap CC dist. will work as well. Depending on what type of ECU u have, (MAF OR SD) will determine what else you will need

 

The car is gonna be a MAF sensor car. 1990 is the only year they used MAP I believe.

I have heard that you can use the same ECM from a 305 as a 350 with no ill effects. You can keep the same distributor as well, thats fine.

 

well mines 91 and it came stock with SD i believe its 91-92 that had SD, not to mention it could have been converter from MAF already, or it could have been pulled from a 91-92 car and into a NON tpi car. Gotta ask just in case the ecm is just about the same, just needs a new PROM

 

it's a simple swap. since yours is a 86, a 87 350 would be perfect, same wiring. ecm just swap it to a 350 one or just get a chip for the 305 ecm.

 

Oh shoot, you are right. I think they used map in 1990-1991 and switched back to maf in 1992? Either that or they swapped back when the LT1 came out in 1993 because I guess they figured it was just better.

 

You will need injectors and the 350 PROM. The 305 injectors are 19lbs, the stock 350 injectors are 21lbs. I believe you can run up to 22lb. injectors without having to tune.

And just to clear the air, 90-92 3rd gens run SD.

 

350 injectors are 22lbs, 305s are 19lbs. In 1993 GM started using MAF again. 1990 -1992 are SD

 

Some say 21lbs stock, some say 22lbs stock. I am leaving room for myself to be corrected other than somebody's "word of mouth." I DO recommend the 22lbs. I am running the 22lb SVO/Bosch on my 350 TPI car. 24lbs will give you some more room for engine modifications later down the road, but you will have to tune out the extra fuel. Obviously 305 19lb. injectors will make the car run too lean, so do not use them.

BTW, 1993 LT1 cars are not MAF. The LT1 in 1993 was the only 4th gen that still used Speed Density. What does this have to do with L98 tech anyways?

 

Thanks heaps for your help lads, its all stuff i neded to know. Does anyone know if the stock ecm will handle a big roller cam or will it just not run? It sounds like its a pretty easy swap out, the other thing i want to know is with the 9th injector, if i take the vac hose out of the manifold from the rocker cover will it cause problems? I have taken off all the egr and smog pump and stuff i just wanted to know about that hose so i can run a breather pod on the rocker cover. Does taking off the egr make any difference to performance?

 

I know they are hard to come by, but see if you can find a set of siamese runners and a port-matched plenum. Good Bang for the buck with a TPI

 

On the '93 issue you are correct. And excuse me for the insult to L98s. It has nothing to do with L98 tech it was just mentioned in an above post. But you are the first I've heard say the 350 TPI injectors are 21lbs. Every publication I've seen shows the rating at 22lbs plus the fact that my ECM has the $8D .bin from the factory and was programmed for a 22lb injector constant. Were 21lb injectors installed the factory would surely programmed it as such. It now carries a 24lb constant for my 24 lb SVO injectors as well as other programming mods.

 

Just be sure to use a ECM for the year of the engine your using.

The 305 injectors will work fine w/ no problems. They will be small yes,but it does run fine and it does still haul ***....I have done this same swap.

I couldnt justify spending almost $500 for some injectors when I was going to go carb. soon down the road and have twice the power.

 

You will also need to check the Knock Sensor and the ESC module... I had switched over from the 305 to 350 years ago and had to change both these parts and the ECM and injectors...

Good Luck!

 

When I did my swap. I pulled out the 89 305 droped in the 89 350. Plugged everything right up and swaped the ECM. Runs PERFECT. But I was lucky enough to find a donor car of the same year. Your problem is they're not any 350s in 86 that why I said get a 87. It's the closest thing. Or just drop in a ZZ4 in a put your TPI on it with 24#-26# injectors, headers and get a custom chip.