97 vortec v6 to v8 swap

[Will Vogel]

Thanks for letting me in fellas! I have a quick question on this headache........I did the swap, and I'm still having problems with it still running on 6 cylinders. Can you tell me what I'm missing besides not having the right ecm ???

[richard wysong]

did you use the 8 cylinder wiring harness and it plugged into the ECM?  if so change the ecm to the one for the 8, if you used the 6cyl harness it may not have the correct number of terminals in the injector plug

[CamGTP]

Needs a V8 calibration to run a V8.

[Will Vogel]

Um I read before doing this that it wasn't gonna be that hard and it's not hard it's confusing and aggravating. Becuz 1st I went to buy the motor compartment harness out of a 98 vortec 5.7 Tahoe. Wiring was a little jacked up but I made it work at least I thought so ...anyway didn't get that ecm from the wiring from same vehicle so I have a buddy that kinda does shade tree mechanics and he had a ecm from a 98 Chevy 1500, didn't cut it this is how I noticed the v6 was still in it. I don't know where. So I've been through with this harness bcuz of the bad luck I have. So I pulled the harness and went and bought a 99 harness and it's in perfect cond. But my whole main question is will that 99 harness interfere with my 97 fuse box in dash? And the 97 350 ecm that I'm getting tomorrow 

[richard wysong]

98 harness only fits 98 according to GMparts.com. I know because I'm replacing mine. the application description is on that sight but you may need a part number to look it up and that may be difficult because they use your VIN to look it up. the 98 harness came with the underhood fuse box and does not connect to the interior except for the bulkhead connector and the ac wiring that plugs in behind the glovebox so as long as the bulkhead connector is the same you are probably ok with the interior fusebox 

[richard wysong]

it's not an easy job changing the harness, lots of leads come out of the main harness and trying to keep them untangled and routed properly is a test of my patience and I've been doing this almost 50 years

[richard wysong]

the only differences in the harnesses may just be some of the connectors are different. check carefully to make sure its going to work before you start the install if using a different year than the truck and engine. I don't think I would have attempted what you are doing without having the donor vehicle available to get any thing I needed off of it

[Will Vogel]

Okay so I bought a 97 Chevy 15oo 5.7 ecm and it seems like it's doing okay. Sounds alot better when idling. Now my question is this since it's doing a little better what else do you think would cause it to sound like a miss. 

[Will Vogel]

On 2/6/2022 at 5:14 PM, richard wysong said:

98 harness only fits 98 according to GMparts.com. I know because I'm replacing mine. the application description is on that sight but you may need a part number to look it up and that may be difficult because they use your VIN to look it up. the 98 harness came with the underhood fuse box and does not connect to the interior except for the bulkhead connector and the ac wiring that plugs in behind the glovebox so as long as the bulkhead connector is the same you are probably ok with the interior fusebox 

Okay 1st of all I said I bought a 99 harness bcuz all the ones from 96,97 and 98 we're all messed up but, is the 99 a confusing getter for the 97 fuse box in dash? And why does it seem like a miss when idling???

[richard wysong]

so as I found out it could cause problems as the terminals on the bulkhead connector are used for different things. I'm having problems and it's from the same year