I thought I’d give some real world feedback on my cooling lines (Subaru powered) I ran through my center tunnel. When researching this option I saw a lot of posts stating that it would add heat to the cabin and I was concerned about that, but decided I wanted to go this route and find out for myself.

I’ve now put about 500 miles on my car through some of the hottest summer weather I can remember and I have to say I have zero heat transfer in the tunnel. I didn’t do anything to insulate the tunnel itself, but I did insulate the tubes passing through it. I used 1-1/4” alum tubing for the runs and I covered the tubes with a quality pipe insulation from McMaster Carr. I used one piece of insulation and ran both tubes through it. This took up less room in the tunnel vs two individual pieces of insulation and just fit better.

Here’s the insulation I used:

Click to view attachment

Here’s the tubes as the enter the tunnel:

Click to view attachment

Well, I just wanted to post this for others who might be contemplating a through tunnel run. I was almost swayed from this based on what some thought would be a problem vs real world feedback from those who’ve done it. I’m not taking a shot at those who shared concerns, but wanted to give some feedback after running in some wicked summer heat.

Thank you for posting.

I'm working out where to put the coolant tubes for a 3.6L LGX conversion that I'm dreaming up.

Your data point helps!

That bulkhead flange looks SERIOUS!

Nicely done, but so much of that car is exquisite anyways...

So I'm guessing that since the Subi is a cable shifter, and the shifter is on a raised pedastal, that you no longer have shifter cables or wiring harness in the original tunnel area? (also obviously no more shift rod) How about fuel lines?.....are they still in the tunnel with the coolant lines?

I like the idea of routing the coolant lines through the tunnel like you've done....not only does it provide protection vs. being exposed under the car, but it also looks a lot cleaner. Very nice!

Beautiful integration.

Am I seeing a silicon foam gasket material there which acts not only as a seal around the tube and body, but also as an actual tube support too?

What was the initial gasket thickness, 1/4"? I could see a similar use for oil lines going through the body or oil cooler seal to duct on front mounted cooler.

Really nice work!

Real-world data is useful. Looks clean.

I had thought about running my oil lines in the tunnel, same thing I heard about heat. I may rethink that part of my project. Thanks

Yes, 1/4” thick silicone sheet from McMaster Carr. It does serve as both a seal and a mounting isolator for the tubes. I have a similar setup n the front where the tubes exit.

Click to view attachment

Correct, cable shifter. The cables and the harness both go into the tunnel at the rear where the tunnel flares out on each side. There’s room for coolant tubes, cables, and harness. My fuel lines run through the passenger side heater tube, so I’m not heating my fuel.