I'm LS7/570, Tremec T56 Magnum F swapping my 1987 IROC. I've got some experience with this stuff because I LS376/480, Tremec T56 Magnum swapped my 1991 Foxbody Mustang coupe. I used a Dominator and purchased the Holley bracket that mounts the ECU under the passenger seat. I did have to cut an additional hole in the Mustang's firewall because the ECU wiring harness was just a little too short to use a Ford OEM hole through the firewall.

For the IROC, I'd like to use the hole that goes out through the passenger side foot kickpanel. The OEM ECM and C207 wires go through this squarish shaped hole. Has anyone mounted a Holley ECU up under the 3rd gen dash? The Dominator isn't small and it's pretty heavy. Where did you mount your Holley ECU in your 3rd gen Camaro?

 

Here is a picture of the ECU wiring hole:

 

I was reading the title and i was like, you put the dominator on the intake manifold.
I was like what is this guy talking about.

I'm from a different time when a dominator carb was the shiznit..

 

Ha Ha Ha! I can see how that could happen. If you were running a Dominator carb, you were running with the big dawgs!

 

something like that...

 

Yep! That's running with the BIG DAWGS!

 

I mounted my Holley HP ECU under the dash in about the same place as the stock ECU. I ran the wiring out the hole in the passenger kick panel area like shown in your pic. pic. I modified the stock ECU bracket to mount it.

 

Dominator ECM is too large, does not fit under dash. If you want it in the interior and out of sight then it would have to go in the spare tire location or something.

HP ECM does fit but does not support drive by wire. Would have to convert to cable throttle body. Also does not support transmission speed input so you'd have to use a Dakota Digital signal converter for the speedometer.

A GM E38 ECM does all these things and will drive better too. Why not use that?

 

Dueling, thank you for your Holley mounting experience. Yes, as QwkTrip says in the post after yours, the Dominator is physically larger and it's heavy. Surprisingly heavy!

 

I mentioned to my wife a couple of weeks ago that maybe I should buy the E38 ECM, The reasons that I probably won't are:

1. I already own a brand new $3100+ Dominator kit
2. I already own a "non-standalone," 12.3" Holley ProDash that interfaces with a Holley ECU. I have one of these installed in my LS376/480 swapped, 1991 Fox Mustang coupe. I love it!
3. I'm using PWM, brushless fans for engine cooling. I'm not sure if the GM LS7/570 crate motor ECM will control the fan. It's easy to program a Holley to control a PWM fan like I've done in my Mustang.
4. If I can learn how to tune my Holley, that knowledge will apply to my Mustang and my IROC

Having driven my Mustang for just over 1 1/2 years, I'm not super happy with how the LS376/480 runs. It runs great when I step on it but it needs more tuning work at part throttle settings. I'm sure the correct GM controller would run the engine better (smoother) during part throttle, street driving. I do believe that with a lot of tuning work, the Holley could eventually run my engine just as smoothly.

 

I really don't want to mount the Holley in the engine bay and I don't want to mount it anywhere where I'd have to extend the entire wiring harness. Even though I'm very confident in my wiring skills/capability, there's just way too much that could go wrong doing something like that.

Mounting the big and heavy Dominator under the dash near where the stock ECM was mounted would be perfect. It couldn't hang down length wise because it's much longer than the stock ECM. It would have to hang horizontally. There appears to be room for that to happen but I'm not really sure. My complete HVAC box is out of the car right now so I don't really know how much room is available once the HVAC box is back in place.

 

I made a bracket and have my Dominator mounted under the dash. I've got tons of room under there as I have zero creature comforts in my car. But all my harnesses and wiring come in thru the hole where the heater/AC wiring went thru

 

I'm guessing that you used this particular firewall hole:


Do you have the black HVAC box that I showed in the picture in my last post installed in your car? If so, it'll let me know that there is room under the dash to mount the Holley along with the HVAC box.

 

Yep that's the hole I used and I even had to open it up slightly. I did check it before I pulled it out and I didn't have enough room. I thought I could squeeze it in kinda where the factory ECU was but there was no way to keep the ECU in place and then getting the harnesses plugged in

 

Yes. The Dominator is much bigger than the factory ECM and much heavier. ***IF*** the Dominator were mounted vertically like the factory ECM, it would hang way down and be seen below the dash. The only way that I see that it can be mounted under the dash near the factory ECM area is if the Dominator were mounted horizontally using a custom made bracket. All wiring harness ports would face downward toward the floorboard.

thatsupnow, is your black heater/AC box installed under your dash along with your Dominator?

 

Nope my black box is gone. And that's exactly what I did was make a bracket to mount it horizontally under the dash with the harness ports facing downward with the excess harness tied to the upper part of the dash

 

dannyua320,

If you're able to make this work with the factory dash/HVAC setup, would be great to post detail and pictures.

Have been looking at this same idea but haven't solved, and know others have also.

 

The one place the Dominator can fit is laying on top of the under dash kick panel. The panel however is not sturdy enough to support the ECM. But if you can make a sheet metal panel then it could be done.

 

A good spot that I thought of before was inside the passenger fender. Have it mounted on those little rubber insulated mounts as close to the fender/door as possible with the connectors facing forward. The ECU is built for the elements and won't see much of anything back there. Only thing is that as you gradually start adding more sensors/inputs it might be a little inconvenient to have it back there

 

It's the cam. Those hot cam LS3s drive like crap. A cam swap would be pretty rewarding.

 

I'm going to have to install the removed, black HVAC box to get a good idea of how much room is available under the dash. This will have to wait as my current priority with this car is painting the engine bay.

 

My car didn't come with that under dash panel. I think that I've seen the panels for sale at Hawks and on eBay.

I've already said it: the Dominator is heavy! I can see it needing some type of sheet metal panel instead of the OEM, under dash panel.

 

I know these Holley ECUs are designed for the elements but it just seems wrong to subject them to that punishment. That's why I don't want to even consider an underhood location even though my 2002 WS6 Trans Am has the OEM ECU under the hood on the passenger side firewall.

 

This is something that I never considered. I'll have to look into this. Thank you for this information!

 

There's nothing to worry about. But like I said if you start adding sensors, DBW, transmission it might be a pain. 5v sensors and ground are all tied together so you could do 1 wire with a step butt connector and 5 leads for power and the same for ground but once you add a transmission connector is sealed off to the world

 

If the underdash location doesn't work out, all other locations will be on the table. I remember my experience with wiring up the Dominator in my Foxbody. I'd really rather the ECU and the wiring harness plugs be easily accessible.

 

Then you'll for sure want it under the dash where you can make it fit

 

The Holley "Plug and Play" harness will not reach under the dash except by punching it straight through the firewall. You'll need to extend the harness if you want to use the original harness routing through passenger side kick panel. That is unless they offer a longer option than was available many years ago when I wired my car. Also, you'll have to make your own transmission harness for the T56 but you already know that I am sure.

My gut feeling is you will find reason after reason to use a custom harness as this project proceeds.

 

The TPI (550-601) Holley harness should have enough length to run through the fender to the factory ECU location. Mine did, at least. It doesn't have provisions for CoP or a crank trigger, so that was a pain to redo later. But the main harness worked.

 

The LS ones don't tho. At least mine didn't. Maybe the later years did but after running mine thru to everything in the engine it barely made it into that hole where the factory harness came in.

I have also had the tpi harness with an HP ECU and it definitely fits but you still need to plug it off as water will run down the wires into the car

 

I had to cut a new hole in the firewall of my Foxbody coupe for the Holley wiring harness to go through. The wire harness wasn't long enough to use the OEM, oval shaped hole on the passenger side of the firewall that the factory used for the OEM ECU wiring. My Mustang's Dominator is mounted under the passenger seat so I was hoping that by mounting the ECU under the IROC's dash, the wiring harness would be long enough. Doesn't sound like it will be. I may be cutting a new hole in the firewall.

I'd really rather not build my own custom harness if I can avoid it. I know all of the plastic connectors and metal terminals (pins) are readily available. I've purchased some of them and have them on hand. Since I'm **** about things, I'd have to buy all the wire as well. I'd want to use the same colored and striped wire so everything would match what Holley originally built. Way more work and money than just cutting a clean hole in the firewall and using the harness that Holley made.

 

If you were gonna go as far as buying the color matched wiring, connectors etc etc I'd just make a call to HCR innovations and get a much better harness from them that's longer with basically upgraded everything compared to the Holley harness

 

It's amazing how much I don't know! Never heard of HCR Innovations but I just did a DuckDuckGo search and found this:

HCR DIY Kits & Custom EFI Wiring Harnesses

Not inexpensive. However, I'm assuming that I could get them to make the harness the length that I want. If so, I could forget about the underdash mount and mount it under the passenger side seat like in my Mustang. I could use the square shaped<OEM hole out of the passenger kick panel area and not have to cut any more holes in the firewall.

 

Yep you could put it wherever you wanted. And I really really like that relay block on their harness. That would've been the harness I got if I didn't already have mine when I was putting my car together.

Here's a Joe Simpson video of his take on the harness

 

I just watched the Joe Simpson video. He really likes the HCR harness. I'm going to have to think about this harness as it really opens up clean options for me.

Holley does have an unterminated harness:

Unterminated Universal Main Harness

I'm going to assume that there is more length to this harness than the finished harness that came with my Dominator kit. I'd have to call Holley and find out for sure. That being said, in the video, Joe Simpson didn't know how long the HCR harness was, either.

 

I just found this on HCR's website:

Holley EFI Unterminated 15′ Flying Lead Main Harness 558-126

Plenty long.

 

The unfinished flying lead harness is pretty much just a bunch of individual wires with nothing spliced together. Doing the splices is the most difficult task. The work is pretty much equivalent in skill & effort to making your own harness from scratch.

 

That sounds like a lot of work. After watching the videos on HCR Innovations' website and seeing the splices, I don't think that I want to do that. HCR does "ultrasonic welds." I don't really know what that is but I'm sure it's far superior to me crimping a bunch of wires together!

 

Ultra-sonic welding basically vibrates the metal so that it heats up and melts together. Good method with the right equipment.

 

Yeah. I don't think that any of my wiring tools are going to be able to do ultrasonic welding ! That being said, this collection of simple but quality wiring tools aquired over the last 5 yrs has really upped my wiring game!

 

Concerning tools, LS engine mostly has a combination of GT150 connectors and Metric-Pack 150 connectors.

* The ratcheting crimper with red handle is for Weather Pack terminals. Just one of those on the LS engine (T56 trans if I remember right) but there are a few more elsewhere on the car.
* The blue handle next to it has some Metri-Pack 150 and 280 crimp dies.
* You don't have a GT150 crimp tool (which is smaller than Metri-Pack 150).

This thread will tell you which kind of connector and part numbers for each device on the engine, https://www.thirdgen.org/forums/ltx-...lectrical.html

 

Holley uses the superseal terminals at the ECU pins

 

That's right, Superseal 1.0 to be specific. No need for crimp tools though because every pin is pre-populated in the flying lead harness. You'll actually be removing wires you don't use.

The Superseal 1.0 crimp tool is ridiculously expensive. The Delphi Micro-Pack 100W terminal is a shameless copy and you can use the less expensive Delphi tool. Some people even use the less expensive Micro-Pack 100W terminals in the Holley ECM connector.

Prowire also sells a solid contact that can be crmped using Deutsch crimper. You can get an inexpensive set of crimpers from ToolAid. Downside to this terminal though is it has no wire strain relief, so Prowire recommends using a rear cap that supports the wire.

 

Some of the correct crimp tools are so expensive! So expensive that it doesn't make sense for a hobbiest to purchase them. I've found that my blue handle crimp tool is able to crimp different terminals that it might not have actually been designed for. The crimps looked good and I was confident. Here is a couple of pictures of crimped Holley 12.3 ProDash terminals from when I was wiring it up for my '91 Fox coupe.


This blue handle crimp tool really seems to be versatile. I
wouldn't mind having a ratcheting version, though.


These pins look different from the Superseal pins.

I've got a lot of Holley pins and plastic connectors in my electrical stash. Most of the Holley stuff purchased from ProwireUSA. It's nice to have that stuff on hand when you're wiring up a Holley ECU.

 

The Metri-Pack 150 crimp die is too wide for Superseal 1.0, which causes the crimp to pancake before it is tight enough to hold the wire.

The Holley ECM terminal is nearly identical as used in LS1 engine PCM. TE Connectivity calls it Superseal 1.0. Delphi calls it Micro-Pack 100W. A dedicated tool for 100W terminals makes excellent crimps and is much more affordable. (Not to be confused with Micro-Pack 100 which is too small.)

I'm just telling you these things so you can get really good results.

 

I recently did a pretty in-depth write up on building a flying lead harness. May find something useful in there

https://www.thirdgen.org/forums/tpi/...cm-91-tpi.html

I agree the dominator will not fit vertical in the stock location. Instead, try turning it 90* so the connectors face down. It will likely still require a custom bracket, but that would be relatively simple by comparison. Alternative would be what QwkTrip suggested by laying it flat on the kick panel with a custom bracket. It's a chonker of a unit either way

For crimpers, I use a white performance T-18E for 90% of the engine stuff and T-11E for unsealed large cables
Basic T-18 which most places sell versions of don't seem to give good crimps on 18-20ga wires and have terrible ergo for your hands. I had problems with wires pulling free from terminals before switching to the "E" variants

https://www.whiteproducts.com/cetools.php

For small stuff like the Holley CAN connector and E38/E67 terminals, a Sargent micro-pack crimper is used

I use the T-18E #2 setting for Holley ECU terminals, both wire and jacket crimps. Same tool/die slot for 100W terminals too

Monkey fab seems to have the best deal on the holley connector kits

https://monkeyfabgarage.com/collecti...l-stuff/holley

 

Yes. Under that dash mounting of the Dominator would require it to sit horizontally with the J connections facing down. Even with the ECU mounted there with a custom bracket, I'm not sure the stock Holley harness would be long enough to go out the OEM, passenger kick panel hole.

I watched several HCR Innovations videos and the HCR harness isn't much longer than the stock Holley harness.

Pocket, I tried finding an online seller of the White Products T-18E crimper and I couldn't find one. I wouldn't mind a better set of T18 crimpers. Mine have done a good job but they're not the easiest to use.

 

White Products has a phone number listed on their website. Give them a call. I ordered directly from them for all my old crimpers

HCR would probably build a custom harness whatever length you want if you asked. Honestly, just about any harness mfr builds custom Holley harnesses these days, so HCR isn't the only source

 

Fab a panel and paint it flat black. It's hard to see under the dash from either front seat anyway, and painted black would further hide it. Dzus fastener mounting to the dash frame FTW!!

Alternatively, I haven't been inside the HVAC box on a 3rd Gen yet, but have been there several other cars, GMs included. Depending on where/how the heater core is mounted, there's frequently a fair amount of 'free space' inside that box, so you might be able to push the back of the box forward to gain. some space under. the dash? Just trying to think outside the (HVAC) box here.

 

I'll may give White Products a call next week.

Alternatively, there is the Delphi and Sargent brands that I'm pretty sure are also US made tools.

If I were to buy a custom length harness, I'd probably have it made long enough to mount the Dominator under the passenger seat like in my Mustang.