Heat Exchanger gaps sealing

[jtsilverfox]

Just a quick post here to see if I can get any new thoughts (I commented on a similar post elsewhere and only got a couple of replies).

I'm about to reinstall my HEs and was wondering about that gap btwn the 3 header pipes and where they go thru the sheet metal. I notice in most of the HE pictures, that most of them have these gaps. Is there a reason they're not sealed?

One guy mentioned the possibility that the gap is intentional to perhaps provide a place for water to blow out. But, that gap would seem to be a lousy way to do that. And it seems that it would be a place for fumes from oil drips on the HEs, smoke, etc to enter the heating system (altho the fan would usually provide a positive pressure to keep that crap out of there). Or even just the oil drips themselves to seep in there.

I'm thinking of sealing them up with JB Weld and wondering if there's any reason not to (to hopefully minimize any drip smoke/fumes being sucked into the heating system). I did a few of the gaps on the other side years ago, while it was still on the car, and they seem to have held up in the heat and cooling of them.

Any thoughts? (Kevin, Henry, Craig, Wayne, ...?
cheers, jt

[Josh D]

The gaps could be either from manufacturing tolerance or maybe even to allow the primary exhaust tubes to expand from heat and not crack the heat "shell".

Yours actually look pretty good. I bought some that need a little work due to corrosion and welded in some sheet metal to help close the gaps.

JB weld won't work. The heat will just cause it to get brittle and break off.

[jtsilverfox]

Josh: That's some great welding! You do it yourself? If so, as you know, welding seems to be more art than science - it gets tricky sometimes. Is that mig welded?
That 'shell' is pretty thin, as are the pipes (as I found out - thought they were thicker...). One of the tabs that bolt the exhaust pipe to the shell (near the flange that connects to the muffler) had busted at the original weld to the pipe, and I tried to mig weld it back on (just a 1/2" of welding...). Just about had it and was trying to put a finishing weld to a spot, and lingered for a second too long and 'poof' - melted a 1/4" dia hole in the pipe before I knew it! Had it set to the lowest speed & current! Eventually got it closed up with more welding, but made it worse before I finally got it! Any mig welding tips for thin stuff?
And you're probably right on the JB Weld.
cheers,
jt

[Josh D]

Yes, mig with .025" wire and patience. It was pretty thin in some spots where I burned through as well. I'm no professional welder by any means, especially on thin stuff. Cut my teeth on welding up suspension mods, bumpers, and rock protection for my jeeps. It just has to be strong, not pretty!

As you probably already know, key is to go slow and not get an area too hot or it will blow through.

Yours don't even look bad enough to mess with.

[jtsilverfox]

Ok, thanks Josh. Yeah, after I posted last time, I went to good 'ol YouTube and did a search on 'how to mig weld sheetmetal' and got a bunch of good videos. Shoulda done that a couple of days ago before I tried my repair. It'd been a while since I did any welding and forgot how much I forgot - duh!
cheers,
jt