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Old 10-09-2006, 10:18 AM   #1
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Default PCM harness through firewall grommet?

I want to mount the PCM under the dash and need to find out what size hole to drill and where to find a grommet to fit around the harness wires. I know some of the folks around here have mounted the PCM under the dash.

Any ideas? It needs to be fairly large since all of the PCM wires will be running through it.
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Old 10-09-2006, 10:23 AM   #2
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i THINK mines 1.25"

if you pop the covers off of the PCM connectors, you can measure exactly how big it has to be... (the connectors have to JUST fit thru the hole)



for the grommet, i used a rubber plug, and cut the center out to size.. its alot easier to find large rubber plugs then large grommets.
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Old 10-09-2006, 10:33 AM   #3
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Thanks for the quick reply. I will measure tonight. Plug sounds like a good idea. I didn't think the harness would be long enough to run the PCM under the dash, but it is perfect length.
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Old 10-09-2006, 10:53 AM   #4
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You have to go to a junkyard to find the gommet first. 1.25" is way too small. You will need a big gommet. Don't foget the PCM plugs need to go thru the gommet. I got my gommet out of a Toyota Van or something and the hole I cut was about 2" or 2.25". GL
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Old 10-09-2006, 11:49 AM   #5
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2" for me and I made a gromet out of some rubber that I had and a lath.
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Old 10-09-2006, 12:09 PM   #6
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Quote:
Originally Posted by LS1Cobra
You have to go to a junkyard to find the gommet first. 1.25" is way too small. You will need a big gommet. Don't foget the PCM plugs need to go thru the gommet. I got my gommet out of a Toyota Van or something and the hole I cut was about 2" or 2.25". GL
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i started thinking back and you're right..
1.25" is the holesaw needed to mount a clutch master cyl... the harness one was even larger then the clutch hole.

i used a 2 something inch holesaw... i posted exactly what i used, but i cant find it in a search...

my PCM plugs dont fit thru the grommet.. if they did, the grommet wouldnt fit the wires tightly.
instead, i snipped the grommet so it can open up like pac-man, and fit directly on the wires.
this let me get a nice tight seal on it.
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Old 10-09-2006, 12:54 PM   #7
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I found the perfect grommet in the plumbing department at Lowes'..........don't laugh, they have alot of useable little goodies for building hot rods at Lowe's! This big grommet was some kind of garbage disposer rubber piece I think.
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Old 10-09-2006, 02:16 PM   #8
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BINGO! I was just going to suggest the same thing! I got one of those gaskets from an ACE hardware. Its about 2" round, and has 5 or 6 flaps in it that allow you to past things through it.

Atleast it sounds like the same thing you mentioned. It is a garbage disposal piece. I used some RTV to seal it up and to hold the seal in place. Seems to work great.

Oh and I used the same hole saw that I used for the master cylinder. But instead of trying to pass the wires through one hole, I mad two holes right next to each other...so I made an oval. In my opinion, it allowed the plugs and wires to pass through easier, and seems like I took off less material. I may have take off more...but either way. The garbage disposal gasket worked for that too.

Dont you just love the lowes/home depot type places?!? You can find all sorts of good stuf to use in a manner other than directed. haha.

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Old 10-09-2006, 02:28 PM   #9
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Quote:
Originally Posted by ghettocruiser
Dont you just love the lowes/home depot type places?!? You can find all sorts of good stuf to use in a manner other than directed. haha.

Justin
Except for when I need metric bolts and they are always out.

Thanks for the input all. I will check the local home shops.
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Old 10-09-2006, 02:37 PM   #10
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Hardware? haha.... Yeah that sucks. I can usually find what I need at lowes. They have a good selection of oddball sizes and metric. Sometimes its easier to use standard hardware if possible. drill and re-tap to standard. haha.

Good luck! Let use know what you find and post a pic.

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Old 10-09-2006, 03:03 PM   #11
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so, it's not possible to make a 1.25" hole, install a grommit (like, say, wrap a window seal around the perimeter w/some glue) and pass the red connector through, then the blue, then any additional wires? This is what I was planning on doing, but it sounds like you guys are saying it's not possible. Just having a hard time fathoming the idea of each individual connector not fitting through a 1.25" hole. My main beef to my wire harness is about 1" in diameter.

as for Lowes...better tool selection and prices than most other places I go and i have an easier time finding things there than Home Depot (our Ace hardware stores are really small, so i won't mention them).
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Old 10-09-2006, 03:43 PM   #12
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I pickup a grommet at a Good Guys meet in Pleasanton, CA, at the Swap meet area..there was a guy selling all kinds of elec related good, including the Grommet. It was about 1.5", only had to split it some get the connector through. but I use a OEM plastic tie to secure it from moving around and use a little glue to hold it in place..

Not sure where to get one anywhere else. It was made for firewalls. There is another Good Guys meeting coming up next month.. If I go and find the guys again, I will post information back to you guys..

As far as Lowe's.. I once told to Stealth to think outside the box... when trying to find one off parts or services. It has save me a lot of $$$ by using normal services that are not related to the Automotive world. (Welders, sheetmetal, elec, etc).. I get a lot of part, nuts and bolt from the local ACE hardware. The even cary chrome bolts and nuts, grade 8.
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Old 10-09-2006, 03:44 PM   #13
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assuming the hole is round, if you can fit one PCM connector thru the hole, you can then hold the wires to the side, and fit the other one thru.
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Old 10-11-2006, 08:33 AM   #14
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Oh man you guys are cutting corners. I didn't cut my gommet at all. I slid one connector at a time thru the gommet, the engine end connectors not the PCM connectors. Using some oil to lube the inside of the gommet help pushing those connectors thru. Once done I just tape it up and it got a nice seal. My car won't have AC so I have to do everything to keep the heat out of the cabin.
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Old 10-11-2006, 10:03 AM   #15
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Quote:
Originally Posted by LS1Cobra
Oh man you guys are cutting corners. I didn't cut my gommet at all. I slid one connector at a time thru the gommet, the engine end connectors not the PCM connectors. Using some oil to lube the inside of the gommet help pushing those connectors thru. Once done I just tape it up and it got a nice seal. My car won't have AC so I have to do everything to keep the heat out of the cabin.
the ID of my grommet is smaller then the largest connector on either end of the harness... so i had to make a single small snip in it.
i dont think its cutting corners.. its not like i hogged it out to make it fit. its sealed tighter then a dolphins butt.
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Old 10-11-2006, 03:09 PM   #16
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I have a factory grommet off of my car if someone wants to try it, I'll send it to them.
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Old 10-11-2006, 08:10 PM   #17
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Mike, we can check at Lowes or the Ace in Oviedo or the one on Lake Underhill, and they both have tons of Metric stuff,
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Old 10-11-2006, 08:30 PM   #18
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I got some stuff from home depot and ace hardware.the pinks show is on
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Old 10-12-2006, 10:44 AM   #19
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Here is a picture of mine
Click the image to open in full size.
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Old 10-12-2006, 02:48 PM   #20
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Stealth71, your pm box is full.
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Old 10-12-2006, 02:48 PM
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