PCM Mounting Location for 73-87 Trucks?

[NorCalAnthony]

Like the title says, looking for ideas or examples for where folks are putting the computers on their swaps. Did some searching and saw a bunch of stuff for the 67-72 trucks but hardly anything for the 73-87's...

Reason I ask is I'm getting everything together to swap a LQ9/4L80E/NP241 in to my 84 K5 Blazer along with a Vintage Air unit and need to confirm the PCM location so Speartech can start making my harness. I was looking under the dash and couldn't see enough open real estate on the driver's side to mount it up under there and VA unit requires modifying the glove box to fit so I don't think I can put it in or behind there on the passenger side either. I'm thinking it's going to have to go in the engine bay, most likely on the passenger fender/wheel well area since the VA unit will free up a bunch of space, but wanted to see what others have done before. Thanks in advance.

[mongocanfly]

i put mine under the dash on the 81..never again i said....there just isnt much room there with all the hvac...under the seat would be my recommendation...i used a PSI harness and it wouldnt reach under the seat...ive heard that BP harnesses are a little longer and will fit under the seat...if your having one custom made then it would be a no brainer to put it under the seat..run the harness over the trans and up thru floorboard under the seat...no need to bore a hole in the firewall

[NorCalAnthony]

Thanks for the suggestion. I thought about going under the seat or maybe even in the center console but that would be further than the 3.5' from the back of the passenger head that they give you and I wasn't sure how noticable or subject to damage the harness running along the trans tunnel would be. Especially if I decide to just use bedliner on the floors for a while after I remove the existing carpet. It's seen better days and I'm not sure what shape the floorboards are in yet...

[mongocanfly]

If they're custom making your harness can they not make it to the length you want from the back of the head?

[NorCalAnthony]

So they can add extra length but it would add to the cost of the harness. The problem with going under the seat or something similar for me is how to route the harness without it being in the way or getting damaged if I wind up removing the carpet and running bare/bedliner floors (truck will be used a lot for hunting and camping).

[mongocanfly]

You run it under the floorboard..and come up thru the floorboard under the seat...based on what I went thru putting mine under the dash it would have been worth every penny of the extra cost...

[NorCalAnthony]

I hear ya, but I would think running it under the floor board could also cause issues with the exhaust and transfer case linkage that runs along that same area, which is why I'm thinking more and more about just keeping it in the engine compartment where it can be mounted up on the fender or wheel well where it'd be more or less out of the way and relatively free from harm. Thanks for the suggestions though, I think you're the only trying to chime in and help lol.

[skyphix]

Originally Posted by NorCalAnthony

I hear ya, but I would think running it under the floor board could also cause issues with the exhaust and transfer case linkage that runs along that same area, which is why I'm thinking more and more about just keeping it in the engine compartment where it can be mounted up on the fender or wheel well where it'd be more or less out of the way and relatively free from harm. Thanks for the suggestions though, I think you're the only trying to chime in and help lol.

Hah, I am sure there are some like me - following along because we have the same question. I was debating between mounting mine up under the dashboard over the trans hump or slightly to the passenger side. I've already got a few pass throughs in the Firewall that I need plugs and grommets for anyway so I figured I'd use one of those. I was originally going to do it on top of an inner fender but I plan on driving this thing is pretty much all weather that isn't snow or ice so I decided to move it to the interior as an extra precaution.

[mongocanfly]

well from the factory they are on the inner fender...with the weather seals they have they should be fairly watertite...hiding it is mearly a cosmetic thing...i dont have any issue running the harness across the top of the trans...on most modern trans there is a big bundle of wiring going to the trans anyway...

[skyphix]

You make an excellent point, and in this thread, someone mentions the Tejas PCM/Fuse mount and I really like that setup. I'm not terrible worried about aesthetics on this build - its just going to be my daily, so ease of maintenance, access, and reliability is what matters to me.

[NorCalAnthony]

That's pretty much what I'm thinking too as far as it being safe in the engine bay since that's where GM put them on all these vehicles we're using as donors. I actually just ordered one of those Tejas Steelworks PCM mounts right before I saw your post. I was thinking about making something similar to the flatter Gen IV ECM mount but the price is well worth not having to reinvent the wheel lol.