When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Hey Guys,
I just wanted to share some more info with you all.
A month or two ago I posted a "follow along' thread on upgrading the A/C system in my '73. I installed the VIR eliminator, new compressor, new condenser and hoses, etc. and upgraded to R-134. All with very good results. Well, I had to go back into the dash this week to remove my factory AM/FM for a needed repair. While I was in there I wanted to correct two things I had overlooked when I did the original job. One was to add the newly reproduced plenum door actuator link made by Willcox Corvette. This piece became available shortly after I'd finished my system and not before, or I would have installed it then. My original was broken, like so many are, and I had to kind of jig-rig it together but I wasn't real happy with that particular repair. Knowing I would eventually go back in, I ordered the new piece from Willcox and, even though it is outrageously overpriced at $31.95 landed at my doorstep, it fits perfectly and works as intended. On a quick side note, when I was looking for one of these links I was directed to one of the Chevy truck forum suppliers. They did offer a reproduction that looks identical and priced at only $4.49 which is much more in line with where this piece should be priced. However when it arrived it was actually just a hair smaller and would not work with the Corvette. Maybe as Willcox sells more of these pieces the price will drop accordingly. Anyway, it is a good part.
The next thing I wanted to correct that is ALWAYS overlooked is the simple foam seals on the plastic ducting. The GM foam is long ago disintegrated away. In fact I can't recall ever working on a Corvette that still had this foam intact. You all know the complaint of how weak the blower system is in the C3 so I wanted every bit of help i could get. I picked up a roll of self adhesive vinyl foam weather seal at Home Depot for $2.99 for a 17 foot roll. I got the 3/8" wide by 3/16" thick. It looked like a pretty close match to the original size. Cleaned off the ducting with some acetone and just stuck the new stuff right back on. Simple. Did the plenum housing first.
Then the large center duct. And of course both end vents.
I can't tell you what a difference this made in my A/C airflow. I have a strong steady and even flow at the center vent and both outer/lower vents. Much better than before this was done. I know one thing for sure, GM never spent a dime on anything they didn't have to. If they figured the ducting would have worked without these foam seals, they never would have used them. Like anything else, the air will move to the path of least resistance and all those under dash leaks were just draining the flow before it exited the vents as intended. I'm ashamed to say that in all the cars I've upgraded A/C system on, I've never bothered doing this before. I will certainly add it to my list and include it with every A/C repair from here on.
Cheers!
No, a manufacturer won't include things that are unnecessary but there are a huge number of considerations regarding what is "necessary". In the case of automotive HVAC ducts I believe that intentionally loose joints with foam seals are there for noise reduction. Tighter joints and a wrap of tape can be specified just as easily (no need for foam) but that would be prone to squeaks. I see the loose joints/foam seals used in every car I've known.
Yes Mike, you are correct. Maybe I didn't make my point clear enough in my post. The idea is to close the gaps in the ducting by whatever means. I'm sure GM used foam as it was quick and easy. It also picked up any slack in the differences between one car's ducting and the next. I'm sure taping the joints would work just as well in stopping any potential leakage behind the dash.
Great Thread, I will add the foam and door actuator to my AC upgrade list.
I believe the foam was intended for easier assembly/disassembly down the road as GM paid the dealers a flat rate for warranty work back in the day.
The foam was an easier way to disassemble the duct at the joints in a tight space.
But as Mike pointed out the HVAC ducting sealer tape would by optimal against leaks.
It just may be more time consuming to disassemble the individual duct pieces in a confined space in the future if they were wrapped?
I know in my 68 BB with AC, you have to remove the lower AC ducts before reaching anything underneath the dashboard.
Again great thread and thanks to the OP for the pics and tech info.
Marshal
09-18-2018, 01:20 AM
Don't Overlook This On Your A/C Upgrade
