CAMARO69

Haven't found a solid answer on this so I'll throw it out there. I have an 88 TPI 5 speed Iroc and I'm swapping in a 350. It will be a bone stock set-up and I'm switching my 19# injectors for 22's. I need to run a 350 prom which I know but they were all automatics. My concern is will the ecm look for a vss signal, my Iroc has none. Will I have a stalling issue at idle or any other drivability problems. Some have said no issues and some have stalling issues. Just trying to cover all my bases on this. Thanks

eseibel67

I researched this a few months ago, so I do not have first hand knowledge, but this is the best I have until someone can confirm.

1) Use the 22lb injectors.
2) Change to the 350 knock sensor.
3) Your 1988 5 speed already sends the PCM a buffered VSS signal.
4) Since your 305 was MAF, the 350 will run ok with the stock PROM, but you should look into a proper custom tune to make it better.

EagleMark

But his name is Camaro 69, so if the 1988 IROC TPI is in a 69 camaro he may not have a VSS. If it's an 1988 IROC then it will have a VSS but I don't no where on his car, some are in speedometer, not in trans.

And the title is 5 SPEED VS AUTOMATIC PROM? Auto proms and manual proms have many differences not just the trans. If there was never a 350/5.7L manual prom he is going to need to get a custom prom or learn to burn one. A 5.7L auto prom will run it but not correctly and set a bunch of codes...

Maverick H1L

iTrader: (8)

You'll be fine. The tables are slightly different between the auto and manual, and that's it. The ECM is already getting a VSS signal from the instrument cluster (where the VSS is, the yellow box on the back of the speedo head), so there won't (or shouldn't if it's working right) be a code 24.

I know mine's a V6, but still... When I swapped to a T-5, I had no other choice than to run an auto PROM as that's all I had (3 of them, actually). There wasn't much difference when I finally got the manual PROM, and there weren't any codes (except 24 for some wiring glitch). However, your ECM may not like the new PROM and will VERY rapidly flash the SES light.

And no, there was never a 5.7/T-5 PROM as GM never produced that combo for fears of massive transmission blowouts...

CAMARO69

Thanks for the info so far. First to clear things up the car in question is an 88 Iroc. I do have an original 69Z, DZ302 M21 car. Thats when things were simple. Though I do appreciate the computer controlled cars I've been slow to embrace them, so I feel like I'm 20 yrs behind playing catch up. I've been reading back through the 305 to 350 swaps and what stood out to me was that if you kept your 19# injectors stay with your original chip and if you went with the 22# injectors use the 350 chip. I know it will run with the 19's but I want to go with the 22's. Knowing there was never a 5.7/T5 combo I thought there might be problems. Some guys talked about stalling ect. Are there more issues with the newer speed density cars and since I'm MAF is that why it should be easier for my swap? If I can get away with a stock chip that would be great. I just got the car, engine smoking and ready to give up the ghost. I have a low mileage L05 sitting the garage looking for a home. Yes, I do know about the down side to my swirl port heads on this. I'm planning on using the long block, sitting my intake on it. Upgrading the knock sensors, esc and whatever chip I need and thats it other than an exhaust upgrade. Just want to say thanks to everyone and that this site is really great. All the info and help is appreciated.

CAMARO69

Hey, by the way, I never even gave a thought to the yellow box on the back of the speedo being a vss, I was just thinking about the trans end of it.

Maverick H1L

iTrader: (8)

Use the chip that went with the engine, as a rule...

Air flowing through the intake is air flowing through the intake. The MAF doesn't care, it's just there to tell the ECM how much. If you keep the stock 305 chip and drop a 350 in there, the MAF will be over-reporting the air coming into the throttle body, and will put out too much fuel. (As opposed to V6 swaps where the difference is only 17 CI, the difference in V8's is huge and may cause issues). AFAIK, the part number for the V8 MAF is the same between the 305 and 350... The difference being in the tables.
This is just like with the speed density system, but the manifold pressure won't change as does the incoming airflow.

You only need to change the knock sensor, as it's tuned to your particular engine.

CAMARO69

hmmm.....keep the original chip and use the 19# 305 injectors or go with the 22# injectors that came in a 350 and buy an aftermarket replacement chip for a 1988 5.7 automatic car. Guess the bottom line is don't sit on my thumbs and get it running. If it's trouble free then YeeHaw!!! If there are problems then figure it out and learn from it. Just trying to get as close to the right combo the first time around.

Maverick H1L

iTrader: (8)

No... Swap in the 350 chip AND the injectors... The 305 parts will be WAY off, especially the fuel injectors (and we all know what happens if the engine runs too lean ).

If you're going to buy an aftermarket chip, you could potentially order one with the T-5 tables installed as opposed to the automatic tables.