Hell ya I'm finally here thanks to a friend's suggestion it's about time I found this board! Hello everybody. Well here's my dilemma ( any help / advice would be greastly appreciated), I have an '87 Iroc-Z 5 speed 305 TPI to which I recently removed the 305 and replaced the engine with a 350 TPI from my '91 Trans-Am GTA. I have left the wiring harnesses alone as I realized that the harnesses differ slightly between the two years. I also left the computer in the '87 Z which is for a 305 and it has a hypertech chip ( for a 305 TPI). The 350 engine has Edelbrock Performer aluminum heads, Edelbrock high-flow intake and runners, 52mm throttle body, 1.6 roller rockers, and an aggressive camshaft. I now notice the Iroc-Z idles around 1400 rpm upon start up with the 350 in it and it doesn't drop down to about 750 as it usually did when it had the 305 in it. I'll let the car run a few minutes but it still doesn't drop down...even when I get in to pump the gas pedal a couple times. The idle does however drop down to b/n 700 to 1100 while I am driving it and come to a stop. The Z runs pretty damn strong with the 350 and the 5 speed manual, but I feel as thow the 305 TPI computer with the hypertech chip meant for a 305 TPI isn't bringing out the full potential of the 350. I also notice the car backfires a couple times after slowing down from giving it a good "boot". The backfires are really loud almost like a shotgun and I have seen flames shoot out the dual exhaust at night. The exhaust in the '87 Iroc is a 3 inch straight pipe from the headers with a 2 chamber Flowmaster muffler. I am wondering whether this backfiring is due to the aggresive camshaft and also that I am running the 350 with the 305 computer....maybe the computer is sending too much gas through the injectors and it is getting unspent in the exhaust and it is combusting hence "back-firing"?? I would like some advice on whether to keep the 305 computer in there or maybe find someone who can program/burn me a chip for a 350 TPI 5 speed that will work in my '87 computer. I have gotten mixed answers on this question. Some people have suggested I get a chip for a 350 automatic and drop it in the '87 computer.....but I am not sure if I should go through the trouble. Others have told me I'm better off leaving the '87 computer with the 305 hypertech chip and running the 350 with it. Can someone give me some advice?? ( And please no answers like " Kill the fuel-infection and go carburation" lol ) Thanks.

 

The ECM is not your Problem, but the Chip you are using is killing your performance. Get rid of the Hyerjunk Chip. You will need a custom Chip for the 350 or like they say on the DIY Board burn one yourself (if that is a option). You have a Bast--rd combination,
a 5sp & 350 TPI which were never stock. Not a easy problem or solution.

 

my friend steve (ragtop somthing on here) was running his 350 with AFR heads, BIG solid roller cam and superram with the stock 305 injectors and computer for awhile....... he cranked the fuel pressure skyhigh, just to get it to run.... once it reached about 4300RPM the injectors were already maxxed out.



but after swapping to larger injectors and burning a couple proms, his setup is running great... HUGE diff... you really should look into either burning them yourself or getting one burned.

 

George and my brother Bill doing the engine swap.

 

Here's the L98 we dropped in the '87 Iroc-Z from the '91 Trans Am GTA.

 

Were there any issues involved with going from speed density to MAF?