ecm selection for first conversion

[Opas69]

This will be my first tbi conversion: 69 camaro, 700r4, 3.70, 355ci, 9.5cr, 193 heads, melling mtc-1 cam. I have tbi harness and parts from '88 gmc van(7747 ecm) with 350. I have also picked up a 16168626 ecm and a 16197427 ecm. Since this is my first conversion should I use the 7747 and change to one of the others later? Or should I jump in with one of them from the start? (I understand I have to change the pinout) If so which one should I use. Thanks in advance for any help.

[lionelhutz]

I'd recommend you at least consider a Dynamic EFI converted ECM.

Otherwise, the '7427 is likely the best bet.

[Opas69]

I was going to change eeprom and use tunerpro. Would you still say Dynamic EFI?

[89S10_Project]

If I were you, I'd use the 7747 ECU and TBI harness, etc, from the G Van. At least you know it will all work "out of the box" so to speak.This of course assumes the 7747 was a V8 auto application- if not you'll need to change out the Calpak (if possible, not sure if that is able to be done on the 7747).

Get it drivable on something that it came stock as in the factory config. Then upgrade to the 7427. IIRC, the 7427 used an Electronically-controlled transmission. using the 700R4 behind it, you're going to need to burn a PROM.

With the mods you have to the engine, you're going to have to burn a custom chip pretty soon anyway. There's no sense adding repining of the ECM to the pile of stuff on your plate.

[Opas69]

The 7747 is from a V8. I will use the parts from the van and get my car running. I will make the 7427 swap a project for later when I hopefully understand things better.

Thanks for the input it is very much appreciated. Steve

[Six_Shooter]

If I were you, I'd use the 7747 ECU and TBI harness, etc, from the G Van. At least you know it will all work "out of the box" so to speak.This of course assumes the 7747 was a V8 auto application- if not you'll need to change out the Calpak (if possible, not sure if that is able to be done on the 7747).

Get it drivable on something that it came stock as in the factory config. Then upgrade to the 7427. IIRC, the 7427 used an Electronically-controlled transmission. using the 700R4 behind it, you're going to need to burn a PROM.

With the mods you have to the engine, you're going to have to burn a custom chip pretty soon anyway. There's no sense adding repining of the ECM to the pile of stuff on your plate.

I concur with this. Pretty much exactly my thoughts.

'7747 will be the easiest to get up and running, just the slow comms on the ALDL is annoying, but it will work. The '7427 requires more time to get to just run an engine alone well, due to the original application using an electronic trans and the PCM generally freaks out of it's not there and if things are not set exactly correctly to disable the transmission functions.

[89S10_Project]

The 7747 is from a V8. I will use the parts from the van and get my car running. I will make the 7427 swap a project for later when I hopefully understand things better.

Thanks for the input it is very much appreciated. Steve

I am pretty much right there with you. I stuffed a V8 into a V6 S10 Blazer, and went with the 7747 to get it running. I am wrapping that up and looking forward to stage 2: the 7427.

[89S10_Project]

Note to the OP:

As I said I'm in much the same boat as you, except my vehicle was alredy running on a 7747. I have the repower swap complete now, the only reason I am not driving it is a questionable alternator (so I'm upgrading to a stronger unit- the CS130 is out, here comes the AD244- wil post a thread on it).

While repinning isn't a huge deal, the parts involved canbe fiddly, and it can be intimidating to some. You're going to need a wiring diagram of the old and new ECMs either way, here's your options:

-Depin and repin the old connector into the new connector. This may not be possible depending on what sort of pins are used. I've heard folks do it, so doubt it's a concern. As I said, fiddly, and apt to damage a few pins if you don't have proper tools.

-cut old harness off, solder and shrink the new to old. Nothing wrong with this approach, but not everyone has the greatest soldering skills.

-cut old and crimp on new. Absolutely a horrid idea. Crimps fail, especially with small wires. Consider this only if you're a masochist that enjoys troubleshooting electrical on the side of the road when you need to pick up the (now pissed off) wife.

-Fiddleboard. Cut old harness and crimp (then solder and shrink) small ring terminals to the wiring. attach to terminal strips in numerical order. Marry up the proper harness in like fashion. This is the most flexible and durable method. It's actually the way combat systems on aircraft, ships, and vehicles are often connected (Canon plugs are more commonly used, but counterindicated here due to header size).. This is likely what I will be doing.... and when I do it I'll have a 7747 and a 7427 connector coming off- so if things go awry with my 7427 swap, I can simply unplug it and plug in the 7747 and get to work!
The terminal strip can be taped to the ECM body, or located elsewhere in the vehicle. If concerned about shorting across the terminals, you can either get a cover or apply duct tape over it. Once the conversion is complete, simply remove the extraneous plug and tuck it away. Easy, peasy. This also allows a handy way to tap sensor leads for external gauges and the like without concern of crimps failing or wire fatigue.