What's the smallest hole size you can use to run GM loom through firewall?
 

Following on from my 'where did you mount your ECM' it looks as if I have enough cable length to actually place the ECM inside the truck. Phew!

Question is, what is the smallest hole I can drill in order to pass through the loom to the engine?

I have heard reference to it but, after a quick search, have not found a definitive size.

Anybody care to share what they used?

Thanks,

P. :D

Re: What's the smallest hole size you can use to run GM loom through firewall?
 

Figure out you wire bundle size...order a grommet thatll fit it..remember, all your plugs and connectors have to go thru it...then you'll know what size to drill based on that grommet size..
for my psi harness, it's a 2in dia hole

Re: What's the smallest hole size you can use to run GM loom through firewall?
 

Thanks Mongo,

I am using a Speartech harness and have one of those fancy 'split' seals so now I just need to gather up the courage to drill a big hole on my newly painted firewall....

What could possibly go wrong!

P. :D

Re: What's the smallest hole size you can use to run GM loom through firewall?
 

Pic of my 68 C10 engine compartment. You can just see the harness grommet behind the right cylinder head. Start small and open it up as needed. Feed the big connectors thru first. Be careful as you feed the harness thru the fire wall and nick a wire. I've used Speartech harnesses a few times. Top notch stuff.

Re: What's the smallest hole size you can use to run GM loom through firewall?
 

Now that is a beautiful looking engine bay! If mine comes out a 1/5th of that I will be a happy man.

Appreciate the advice, I am going to take the plunge this weekend and start making holes.

Wish me luck....

P. :D