Hey guys, I just put a 350 in my 84 T/A and was wondering if I have to swap or otherwise reprogram my original 305 ECM to accomodate. It's not EFI but it does have a CC distributer and CC Q-jet so this might be the wrong forum, if it is I apologize. Also, where could I go to do this or who do I talk to if anyone has a name of someone to contact who can do this. Thanks!

yes, the ecm/prom goes with the engine, so if you did an engine swap, you need to swap the ecm/ prom otherwise you will have all kinds of problems like we did. had the wrong prom/ecm and our 89 formula would low idle, stall out, etc. we put the correct prom in it and it runs like a top!

i have an ecm available out of a 85 firebird trans am with 350 corvette motor multi port injection. it looks like this ecm has a permanent prom (just pulled it yesterday) check parts for sale interior

I put a 350 in, but it isn't anywhere near what it was in the vehicle it used to power. It's much, much better Where would I get, or who would I go to to get an ECM that could run it properly?

ok i got a simular prob of my own i cot a 5.7 out of "91" truck cant support that myself had no computer or wirirng with it it wont idle or stay running how do i fig the correct computer and prom

1987-1991 chev-gm 5.7L "TBI" light duty(?) truck used a 1227747 ECU. 2732A prom.

Do I go with one out of another vehicle that had a 350 that is programmable or do I contact Hypertech or Jet and have them make me one that I can put in? I guess that's the question. Also, since my car isn't EFI, but has the CC Carb and Distributer, is that still "programmable"?

The CC systems are much more forgiving about changes to the engine than injection systems are. The carb still works pretty much as usual, and the needed jetting changes are taken care of by the feedback from the O2 sensor.
I'm not saying you won't run into some driveability problems though, and the secondaries must surely be tuned (carb question).
You obviously upgraded the 350 a lot from its initial state so you can't use an ECM & a prom straight out of the initial application either.
Just try to run it with the old 305 program and see how it performs. You could run into knocking, or not getting it's full potential.
Are you prepared to get an aldl cable and log data, and maybe tune the program?
Better try posting a question about this in the diy prom board, I'm sure you'll get better answers there. Include more engine details, like pistons & compression + intake maybe.

I will post over there and see what people say. I've been driving it for the past 200 miles and I haven't detected any knocking that I can perceive and the engine runs really strong. I know the carb probably needs to be jetted for the 350 but I'm trying to solve an idle stall/stumble problem as well as some overheating at speed that might be due to the engine trying to lean itself out (from false readings or incorrect readings made by the ecm from the o2 sensor).

Set the timing, adjust the carb( idle mixture, mixture control solenoid, rejet, etc.), and you will be fine. Depending on the original engine that came in your car, you might want to bump the initial timing up. I think the LG4's had 26 degrees and the L69's had 32 degrees of total advance.

GM made a chip to use with a later model ecm for their 350 crate motor conversion. The info about that is posted on the boards somewhere.

I've done the 350 swap and the car ran fine with the stock 305 ecm.

The timing is at 12* advanced with the distributor unplugged, not sure how much total that gives me. Never done a carb rebuilt or adjustment like that so I'll have to look into learning how to do that.

The factory chip for the L69 provides 32 degrees total advance. I think the factory setting is 6 degrees advanced with distributor unplugged (check your emmis. label). That would put your total at 38 with it set at 12 initial.

Bringing this thread back from the dead a bit...

I had the car dynoed and the shop set the engine to 36* total timing however shortly after that (the car ran pretty good for about a week), it started giving me problems where it would stall out at stop lights and not want to run at all when cold.

Fast forward to now, the car had been sitting for about two months while I got new plugs and plug wires (had to save up for them lol) and I am having idle issues where the car just wants to die all the time. As long as I keep my foot on it, it works great but as soon as I let it do it's own thing..it dies....I even cranked the carb idle screw all the way in which should make it run around 1800 rpm or so.

You think this is an ECM issue or something else?

its not the ecm,that only fine tunes timing and fuel slightly,you can unplug everything from the carb except the choke wire and it will run.in an emergency i put a ccc quadrajet in a non computer truck and it ran fine,a little rich and not optimized but not stalling or anything,you may have a carb or fuel problem.the computer stuff on those carbs is a joke. and dont buy a chip for that setup save your money for a non computer quadrajet and vac advance dist.

I would love to do that but I need the CC qjet for emissions reasons.

emissions on a 25yr old car? around here anything 25yrs old is emissions exempt. when my bird hits 25 im getting antique plates, then its safety and emissions exempt..............i can hear the sound of headers and turndowns already


if your motor is a mild build and your really stuck with emissions testing i would go with a stand alone tbi setup.it would run you around $400.
just somthing to think about.tbi and a new cat would pass emissions no prob.

In my state and here where I am stationed it 1984 is the cutoff year...so I'm stuck with it.

Do some digging and see if swapping to a full TBI set-up would still be passable.

In most cases the e-test stations wouldn't be able to tell the difference anyway, especially if you keep the stock or stock looking air cleaner, and other parts.

But it sounds like you have a mechanical issue of some sort, the CCC set-ups were really a last resort attempt at pacifying the American public that doesn't like change and is scared of having a "computerized" car. They didn't do large fueling control, like was said early.

I may look into that TBI set up...

Just getting fed up with this thing. Spend a ton of money and 8 months later it still doesn't work right. For what I've got into it now, I could have bought a low-miles practically pristine GTA....

http://www.larryselectricsite.com/tbi.html

$275 for the tbi harness,i have a 350 tbi you can have if you pay the shipping.then all you need is a ecm and fuel pump,and intake manifold and your done.

these cars are money pits..................

but you should find your problem before you go spend any more money and if it comes up a bad carb go from there

Does not sound like an ECM issue; I would check for a vacuum leak to start.

Aye, I'm just looking into options at this point. I still have my stock original carb, only difference between the new one and old one is I changed the secondary metering rods in the new one to support the larger motor/cam. I'm going to be checking my module and coil today, from there the carb and after that????? lol money pit is right. I just never figured on being able to drive it 2 months out of 10 after getting the motor in it. hehe