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Chuck I would run this in all your seams it also adds 250# tensile strength, not that it’s a big deal. It smooths out real nice with a foam brush and add your insulation to the outside, you’ll have a science experiment going in no time. When I started in the trades I started in sheetmetal then moved to pipe. The state jobs we did had to static air test to 10 or 15” of water column so every seam on the duct had to be sealed. They used this stuff, always held preasure.

Im thinking of using this stuff as my seam sealer.

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Steve

My build : http://www.locostusa.com/forums/viewtop ... 35&t=17160

MGB/GT V8 5.0L. viewtopic.php?f=36&t=20782

I would add a dimple to the bottom center and drill a hole in it for a drain tube You are right about condensation, it will form in the box. I would also think about painting the inside to help prevent corrosion.

The box looks great otherwise

Thom

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Thom

I don't see much differential temp going on in the confined space inside the dash and air leaks at the seams, rivets, and connections. I don't see insulation on the outside except to protect other parts from rubbing the plenums and never see any inside. Since these are normally 1/8 inch plastic, they provide more insulating than aluminum sheet. If any, I would add a thin, adhesive backed, foil covered bubble sheet to the outside of the plenum.

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All good answers. Thanks. Given the space available, I cannot add any appreciable insulation on the outside of the plenum. It is a tight fit as it is. The only possible location is inside the box. So that begs the question, am I better off leaving it as is or add insulation inside and if that, then what kind of insulation? I initially thought some closed cell poly-something foam that I already have about 3/8" thick. I cut some up today and when packed inside, it appears to be too restrictive for the airflow coming from the A/C unit. The only other alternative I have on hand is the poor man's sound deadener and insulator, roofing patch. It is aluminum faced and self adhesive. I used it under the carpeting in my'79 MGB. Contrary to many internet reports, this has no detectible odor. It is only about 1/16th thick. I don't see any insulating difference between putting this inside or outside except that a) the alum foil layer is not subject to damage when on the inside and b) the thermal mass of the aluminum foil is less than the aluminum box structure and should create less, if any condensation when the A/C is initially turned on. While not a lot of insulation, it is some. Better than nothing I think. Last comments before I commit to insulating it inside?

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Chuck.

“Any suspension will work if you don’t let it.” - Colin Chapman

Visit my ongoing MGB Rustoration log: over HERE

Or my Wankel powered Locost log : over HERE

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I’d seal it up on the outside or inside with the caulk and leave it. You’ll
Be fine, the coil should wick out your moisture.

_________________
Steve

My build : http://www.locostusa.com/forums/viewtop ... 35&t=17160

MGB/GT V8 5.0L. viewtopic.php?f=36&t=20782

Outside unless it is closed cell. Open cell will promote mold growth



Housings for modern HVAC systems are almost universally 20% talc filled polypropylene, and rarely have condensate issues (our housings were 1.4-1.8mm thick in non-structural areas.) Get some sheet ABS 1/16" thick or so and secure to the housing and you should be adequately insulated from external condensate

Steve, sealing is not an issue. What minor gaps are there will be overshadowed by the always-open outer dash vents. There is a door that shuts off the feed to my plenum when the heat and/or defrost is called for.

twentyover, thanks for the info. It reinforces my thoughts.

I feel confident in that I won't have many major issues with condensation. But then again, I fall back on one of my engineering go-to phrases, "If you aren't testing, you are only guessing." I thik I will find out much later if it works.

The pics below show how tight the area is under the cowl and behind the dash. The notch in the upper rear of the plenum is to clear the defroster hoses. You can barely see 2 of the 3 ports or the A/C unit that now feed my plenum. The plenum has to be lifted and then placed down over the 3 ports. That is where the overall height is very tight. No room at all for external insulation. The plenum just sits on the A/C unit. I will add a couple of screws to secure it to the horizontal tube that runs from side to side. Perhaps some felt will be added to the bottom of the plenum to seal that joint. Maybe not. Who knows what I'll do? Certainly not me.

_________________
Chuck.

“Any suspension will work if you don’t let it.” - Colin Chapman

Visit my ongoing MGB Rustoration log: over HERE

Or my Wankel powered Locost log : over HERE

And don't forget my Cushman Truckster resto Locostusa.com/forums/viewtopic.php?f=36&t=17766

Sometimes we miss the obvious, The box is in the interior, if it leaks "cool air" thru the box- it goes into the "interior"! No losses to the outside.

Thom

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Thom

But it depletes air volume available at the vent. Air volume and vent directional control are critical to passenger comfort. Look at an oem blow molded air ducts- frequently use pin and screw locks and foam seals to make certain treated air makes it to the vent.

Further thoughts- may want to setup a test to determine if HVAC outlets should be segregated. Long run of convo tubing will generate a pressure drop, reducing airflow to the outboard outlets, favoring the center outlets. May want to setup proposed hose lengths and routing, power the blower motor, and see if the horizontal outlet velocity stratification is acceptable.

I’m getting some home things being taken care of. Gosh darn life gets in the way of the fun stuff!

I'm slowly working on the GT, figuring out where the systems are going to be located. How it would be serviced in the future is one of the primary considerations. I managed to nail down the location of the heater hoses thru the firewall and made up some copper runs from the firewall to the HVAC system. Then went to work on the wiring for the same. I think the wiring from the control to the hot water valve will have to be lengthened. I want that inside the engine comp't to minimize the chance of any leaks causing interior problems. Beyond that, I mounted the 2 relays for the system and provided ground studs as required. I also set the angle for the automatic shifter. I'll need to see if there will be enough room for it when the trans is installed.

I'm still in a quandary as to where to locate the PCM. There are 3 big plugs with maybe 60 or more wires that have to run a certain direction based on the connectors. I can't seem to find an easy location inside the car that flows well and doesn't take up too much passenger leg space. I have seen at least 1 build where they mounted it behind the mud shield, in the fender cavity, outside the interior comp't. I don't want it there as I may weld the fender in place. In the Camaro, the PCM was mounted in the engine compartment. I don't want it there either. I am convinced at the moment that it must reside inside the car. I keep putting off this decision. At some time, it will all work out, I'm sure.

In the meantime, I work on determining where major stuff will be located. Soon, I'll have to take this off the rotisserie in order to test fit the power train. That is when I'm not doing home maintenance and repair.

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Chuck.

“Any suspension will work if you don’t let it.” - Colin Chapman

Visit my ongoing MGB Rustoration log: over HERE

Or my Wankel powered Locost log : over HERE

And don't forget my Cushman Truckster resto Locostusa.com/forums/viewtopic.php?f=36&t=17766

Looks good Chuck. I’ve been too busy traveling. Cant you make a compartment back by the old battery boxes for the PCM?

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Steve

My build : http://www.locostusa.com/forums/viewtop ... 35&t=17160

MGB/GT V8 5.0L. viewtopic.php?f=36&t=20782

I thought I'd end up without a rear seat setup and just make a flat surface from behind the front seats to the rear. rear seats are virtually useless. If I do that, almost a certainty, then there is a lot of room there to be used. For the PCM, I think I would have to extend all of those 60+(ish) wires as they probably are not long enough to reach the engine. I may end up putting the main fuse box there. Maybe even put a BT amp in there to play from my smartphone.

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Chuck.

“Any suspension will work if you don’t let it.” - Colin Chapman

Visit my ongoing MGB Rustoration log: over HERE

Or my Wankel powered Locost log : over HERE

And don't forget my Cushman Truckster resto Locostusa.com/forums/viewtopic.php?f=36&t=17766

So just about the time I get back to working on the MG, my wifey decided that she wanted to do something for me. She had arranged for my 2 son's to come and build a shed on LaborDay weekend so that I would have more room to work on the MG in the garage. Nice idea. But she wanted me to figure out what size/type of shed I want/need. That took some time, and it ended up that there wasn't a prebuilt that fit my wants. Design-a-shed time. Then there was ordering the material including some special order stuff. Add to that, tracking the declining prices on lumber over the last month. Got that figured out a few days ago and got a $800 reduction in my purchased, but not delivered yet materials. Scheduled delivery for today.

In the mean time, Son#1 had his 6th (or is it 7th ?) annual Rib-off so I had to compete there. That took another couple of days. I came in 2nd out of 8 entries. Not too bad for a once a year effort. It is my 3rd year in a row that I came in 2nd!

I had to replace the stockade fence post along where the shed will be. It was leaning in towards where the shed would be. That took another couple of days. Remove the concrete encrusted 4x6 and put in a new one set in concrete. I then removed a tree that also needed to be removed. Then entire line of trees along the fence are dying a couple each year. This one was not longed for this world. Might as well take it out now when felling it won't damage the soon-to-be shed.

Next up was getting the yard laid out and I started setting the 15 concrete blocks. I actually got 8 done up to yesterday.

Then today happened. We got a call at 5:15 AM. Wifey's step mother passed this morning. She had been ill for a few years and really went downhill the last week or two. Spent the day going to help make arrangements, took a few hours off of that to drive back home to receive the shed materials, then back again to rekey the locks on her house. The next few days will be focused on her arrangements. Then back to the shed building. Wifey, who was to help in the shed build, will be occupied with getting the necessary legal stuff sorted out as she is co-executor and co-trustee.

Funny how life happens. Someday, I hope, I'll get back to working on the MG. Before that I have a couple of doorframes to repair and a few bits to be addressed before the painters come in early October.

So glad the site is back up and operating, Thanks Dave!!!!!

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Chuck.

“Any suspension will work if you don’t let it.” - Colin Chapman

Visit my ongoing MGB Rustoration log: over HERE

Or my Wankel powered Locost log : over HERE

And don't forget my Cushman Truckster resto Locostusa.com/forums/viewtopic.php?f=36&t=17766

Omg we had very similar months. We finally had our new fence installed. Ever shop aluminum fences? Honest to God my entire Alice budget is in the 250’ of fence, and we didn’t go hog wild, absolutely ridiculous. Life gets in the way, I hear you Chuck, gotta laugh and love it.

_________________
Steve

My build : http://www.locostusa.com/forums/viewtop ... 35&t=17160

MGB/GT V8 5.0L. viewtopic.php?f=36&t=20782

This is the progress on the shed up to end of yesterday. My son came down from the Soo to help out, along with a couple of friends for a couple of days. Today is a day of sorely needed rest. Good news is that at 67+ years of age, I can still shingle a roof, although I am not as fast or as confident of my movements up there as I used to be. I think this is my last roofing job.

_________________
Chuck.

“Any suspension will work if you don’t let it.” - Colin Chapman

Visit my ongoing MGB Rustoration log: over HERE

Or my Wankel powered Locost log : over HERE

And don't forget my Cushman Truckster resto Locostusa.com/forums/viewtopic.php?f=36&t=17766