A few years ago I did a 350 swap in my 85 Iroc. I changed the ESC, knock sensor, and installed 22lb injectors. I also installed headers and a high flow Y pipe. The car never ran right so I purchased an ECM for an 85 corvette because I knew that it had a 350. It ran worse with the corvette ECM. It runs better on the ECM for the 305 that came with the car. The car is really rich and stalls out sometimes. I assume that the problem is with the prom and that I need one custom made for the setup I have. I have spent some time researching looking for an answer but I havent found much. I have a feeling most people are going to say I need to upgrade my 870 ECM to the 1227165. Is the upgrade my only option? I was told by a local shop to go back to the stock 19lb injectors. I was also told I could have some other issues going on. The car has been sitting a while and I am really hoping to get it going again. If anyone can help me figure out the problem I would really appreciate it.

 

I forgot to mention that the 350 motor is a GM performance crate engine ( http://www.summitracing.com/parts/NAL-12499529/ )

 

I put the same exact engine in my 85 with 24lb injectors like 4 or 5 yrs ago. Its very hard to find someone that tunes 85 proms. I searched on here and had mine done by Jamie at LSRacing chips mail order tune it. I remember seeing something about him not doing it anymore. But it might be worth it to search his name.

 

I have an ECM out of an 89 TPI 30. Let me know if you are interested.

 

I have decided to just do the 1227165 swap. I have a few questions about the swap. I plan on buying the burn off relay connectors from TPIparts but they offer 86-87 style connectors and 88-89 style connectors. Is one better than the other or does it not matter? Do I need a newer MAF sensor?

 

http://www.eecis.udel.edu/~davis/z28/index.html

 

I more fond of the newer style relays like acdelco 15-8240 pigtail PT1115

 

I have read this page a lot. Its very vague with its instructions. It doesn't say whether to use the newer style or the older style but it does show pictures of both.

Thank you, I will order the newer style relays and connectors.

So now all I need to know is if I need a newer MAF sensor? I did find some people that said you do not have to change it but is there any benefit to swamping to a newer MAF sensor?

 

I had a similar problem, and like you, I chose to do the 165 ECM swap. To give you some perspective on the improvement, my car ran a best of a 16.1 with the 350 and the original ECM, and I've run a best of a 13.6 with the swap. There were other changes, but they were mostly small with the exception of a 700R4 to T5 swap, but that sure didn't account for the 2 1/2 second drop. Most of it was getting the motor to run right.

To that point, the reason that you're running stupid rich is that the factory tune is set for 19lb injectors, and you're using 22s. I was in even worse shape, using 24lb SVOs, which are about a 26 or 27lb injector at GM fuel pressures. That 350 you've got is a fairly mild 350, so I'd be willing to bet that if you went back to the stock 19lb injectors, the car would run worlds better than it does now. I'd give that a try as a holdover while you do your ECM upgrade.

 

I think the 85 is a digital maf and 86-89 are analog. I think the 86-89 will work on a 870 ecm but not the other way around not 100% positive though.

 

You're backwards. An 85 MAF will work on an 86-89 system, but the newer one won't work with an 85. I ran my 85 MAF sucessfully for quite a while with my 165 ECM and my MAF counts were accurate. I'm not 100% sure about what type of signal the two different styles send, but I suspect that the 85 used a pulsed signal (hence the "digital" reference by some people), and the newer ones use a variable voltage signal. The 165 ECM most likely has some sort of high pass filter on it that smooths the pulsed signal, providing a variable voltage that's close to what the new MAF provides.

 

I must've gotten lucky. I drove mine for like a month before I got my tuned chip. But I did find an old hypertech chip in there. Still drivin it today. I would like to have it retuned because Ive done a few more things but cant find anyone to do it. Runs rich but otherwise fine.

 

I am going to do the ECM swap asap. I should hopefully have all the stuff needed to do the swap by next weekend. Thanks for the info on the MAF sensor, that is one less thing I have to buy.

 

Just a pointer on the swap... an 86 harness is going to be the easiest to retrofit. I used an 87, which was very similar as well, with the only real difference being the dual fan connections, but I just tucked the 2nd fan plug out of the way. The 88+ harnesses are less ideal because the alternator and a/c compressor plugs are on the wrong sides of the motor. The bulkhead connector that goes through the passenger side kick panel is bigger on the new harness, so you'll have to enlarge that hole approximately 1/4". I think I had a power line off the starter wire that was slightly different as well, but I really can't remember... it's been a while. Overall though, it's mostly a plug & play swap.

 

I was planning on leaving the relays under the dash with the ECM. Is there any reason why people put them under the hood? I have an adjustable fuel pressure regulator, any suggestions on what that should be set to?

 

Fuel pressure must be set with the regulator vacuum hose removed 38-42 pounds. Since this is a mild engine and you dont need to compensate for a large cam I would run it around 38.

 

I have an 870 ecm running my 350 with no problems. I also have 24lb injectors in mine but my cam is a little more wild. It does run a little rich but I have been driving it this way for years..

I think you need to find out is wrong before you add another variable to it.. Just my 2 pennies.

 

I did about 1500 miles after the 350 swap. It ran but if you were behind the car it would burn your eyes from how rich it was. It started to foul plugs. The car ran perfect before the swap. It had 120,000 on the 305 so My dad told me we should have it rebuilt. I wanted bigger and better so I decided to get a 350 instead. When the 350 was installed the transmission was rebuilt and all the sensors were replaced except the MAF sensor. I don't remember getting any trouble codes after the swap. I am hoping that the ECM swap will help make the car run better. It will finally have the correct PROM for the 350 and I wont be able to blame the wrong PROM as my problem anymore.

 

I swapped in a bone stock TPI 350 out of an 88 IROC into my 85 IROC originally with the 305. I used a microtech maf (with a chip, not the crappy wire), my stock ECM and had a custom chip made that mimicked the 85 Corvette 350 with a few other "custom" mods. Used new 22 lb injectors and it has run like a dream so far. I couldn't be happier. Went through emissions CLEAN CLEAN CLEAN and flat out runs fantastic. Starts with half a crank. Lays rubber all through first and halfway into second.

I am thinking your problem lies somewhere other than your "tune". Especially after sitting. The computer for the 305 and 350 is exactly the same part number for 85. The only difference is the chip inside itself.

Also, I bought the Microtech MAF after 2 factory ones crapped out on me. It made a WORLD of difference just on the 305 when I used it. Ultra smooth idle, better off idle response and better gas mileage. I would recommend one to anyone who wants to keep their maf setup but is having issues with their factory maf.

 

When I get home tonight I will see if I kept the paperwork that came with my chip when I had it made. If so, I will PM you the guys name and info. I am very impressed with the way my car runs after the 350 swap using the chip I had burned. I had to answer about 5 questions that were asked and then it showed up in my mailbox.

 

So I did the ECM swap and it didnt fix the issue. I was talking about it with a neighbor who was a mechanic and he offered to come down and take a look. He suggested that we do a leak down test to make sure there was nothing wrong with the motor. As he was about to test the first cylinder he noticed that the Harmonic balancer was broken. I looked back at pictures I had from when I did the 350 swap and it was broken back then. After I installed the new balancer I checked the timing and I ended up having to pull the distributer and reset its position. The car runs so much better now. It still smokes a little but atleast I can drive it now. It sat for way to long. This is a pic of the balancer next the the new one and a few of the car.