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MG MGB GT V8 Factory Originals Technical - Air Conditioning Simplified

Lately I have been thinking about adding AC to the V8 but want to keep it simple. So here is my proposed approach:
1. Keep the existing heater and two speed fan. Mount an evaporator in the outside air box by cutting an access panel from inside the car. In other words, all of the air coming into the interior would pass through the evaporator much like the modern systems used today. The air box would also serve as the condensate drain box.
2. A diveter box similiar to the present diverter mounted on the Smiths heater box bottom would be use to direct air to two dash vents (I know four would be better for distribution) in the center of the dash. This second diverter would allow the air to go either to the vents or defroster outlets.
3. An extra switch would activate the compressor clutch.
4. Retain present mechanical fan on front of engine (I use a TR7 fan) and add a shroud to increase efficiency.
I think this would work and allow me to cool the car sufficiently with the hardtop on for long trips to meets. I have a stowaway soft top that I could use when I arrive at the meet and that could be plucked off and stored in the motel room.
Any insights and opinions??
Can any one give recommendations on the availability of a custom evaporator core?
James Johanski

Hi James,
I am right in the middel of adding A/c to my 74 roadster. I have researched all available A/C evapaorators, emailed people on this list for input and even removed the dash so that I can measure the avilable space. I have come to the following conclusions
1. There is not way to fit an evaporator behind the dash - not enough room.
2. The RV8 type evaporator that goes under the dash on the pasenger side takes up too much "foot room".
There is no way anything will go in the "airbox" if what you mean by that is the space where the air comes in through the grill at the top of the scuttle. The only way would be to strip down an existing evaporator and then you would have no fan.

My end solution (suggested by others more wise than me)is to use a modified Hot Rod Air Elite in place of the existing heater and cut the firewall out to make it fit.
If you (or anyone) need dimensions etc, as I said I am right in the middle of this so I can take measurements, photo,s etc if needed.
Regards
Tony
Tony Bates

Tony,
I aggree with most of your conclusions except for fitting an evaporator into the airbox. Perhaps I should have used a more accurate term and said evaporator coil or core. The only item that I intend to install in the air box space would by the evap core and perhaps the expansion valve. The space is limited but the car is small and does not need a large evaporator. The access would be by cutting an access panel from the inside of the car behind the dash. All heat/cool/vent air would enter the interior through the airbox passing over the evap core first pulled in by the heater fan, and into the heater box. Over the heater core and then either to the floor or to a second diverter box to dash vents or defrost vents. The condensate would drip into the air box and use the existing drain for escape.
I believe my fan when supplied with sufficient voltage via a large supply wire has enough volume to distribute the air even with the additional restriction of the evaporator on the air intake. This system would permit the least amount of sheet metal cutting. The access panel would encompass the area of the existing direct vent holes in the air box and the cold air vent door, thus allowing sufficient access to install the evap core, the expansion valve and replacement diverters/baffels. The evap connections could be made on the engine side of the fire wall left of the heater and be hard tubed to the compressor (a short piece of flex line at the compressor) and condensor.
Parts needed are an evap core with expansion valve, a compressor, a condensor, drier, associated piping and hosing, vents and duct hose, a switch to activate the compressor circuit and voila!---a really cool V8.
So--whatta think now? Am I crazy or what???
James Johanski

Here's how someone (Jim Stuart) did it.

http://mgbv8.com/air_conditioning.htm

Wayne
Wayne Pearson

Hi James,
I understnad now. This is a really interesting idea. I have just measured the space between the two firewalls where the airbox is, it's a fraction under 3 inches so presumable that's the max thickness of the evaporator core you can use, but it only needs to be A/C, not A/C and heat. It was easy to "dissassemble" my A/c unit, but the core is nearly 4 inches deep.
Regards
Tony
Tony Bates

Tony,
I have contacted Vintage Air to see if they could make a special evaporator that would fit in the available air box space. I will let you know what I find out.
James Johanski

Try Dave Stutts at Hot Rod Air as well, he's very helpfull
www.hotrodair.com
Regards
Tony
Tony Bates

Tony,
I have heard from Vintage air and while they are courteous, they don't seem to be willing to do something different. They don't sell custom evap cores, nor could they tell me who does. I have found a web sight for Frigid Air which may have what I need.
James Johanski

Another thought on this topic-

Some older A/C evaporators use a copper tube with aluminum fin swaged onto them. It may be possible to unsolder some of the copper tubes from the refrigerant circuit and re-plumb them for water from the heater. Use this coil rather than the heater coil and you integrate all the heat exchange into a single package.

You would need a good quality water valve to control outlet temperature, and maybe a vacuum shutoff valve like the GM ones for when you go full cold.

It may be small enough to get into the heater box if you hacked on it a bit so there would b no cutting on the car

Or maybe not- I don't know if this would even work.

Regarding using the existing fan motor- may want to look at a big horsepower blower motor from a GM along with a multi speed switch. In zero body pressure testing (I was involved with a lifetime ago) we found that when you got 225-250 cfm airflow from a blower through the cars (Cavalier, Sentra, Corolla size cars) you seemed to get comfortable, while less than 175 cfm you sweated. Using modern squirrel cages, the good numbers required about 20 amps to achieve 250 cfm- so I'm planning on a high blower relay and a 12 ga wire to the relay

http://mgbv8.com/air_conditioning.htm seem to use a vintage air mini-cooler- is this the current darling for this installation, or is there a different model (Hot Rod Air Elite?) that has surpassed it as the best/easiest/more practical installation (I'm adding air to my MGC-GT). I'm planning on using a late '70's 6 gauge dash with two center vents and I'll add outboard vents on the LH of the gauge panel and right of the glove box (which may get sacrificed in this deal).

Tony- I'd like to take you up on the offer of pix, sketches, etc. I'm planning on bringing the car home for modifications (currently in storage while rebuilding the engine) including A/C evap install, front and rear swaybays, and rebushed front suspension. I've got a week in early October while SWMBO is visiting relatives.


Greg Fast

Hi,
From my research, theHot Rod Air Elite "seems" to ne the favorite. I spoke to a rep from Vintage Air last weekend at a show about their "Mini" model that is in the photo's from Jim Stuart. The rep suggested I use the "Gen II Mini" as it was more powerful etc. He then went so far as to say that he wouldn't sell me a "Mini" as I would be dissapointed. Unfortunately the Gen II Mini appears to be too big to fit. Jim Stuart fitted a Hot Rod Air Elite in his second A/C car and recommended them to me and others (Robert Milks). I met with Hot Rod Air also at the same show and the service and help was excellent, I bought an Elite at the show from one of their dealers and started hacking at the firewall the following day. There are two mod's that need to be done to the A/ unit.
1. The defroster vents need to bee turned around and point in the opposite direction to normal. Either Hot Rod will do it if you order from them or you can do it yourself, it took me about 30 minutes.
2. The fan must be dissconnected and reconnected with a piece of ducting about 4-6 inches long in order to clear the hood hinge. Greg, email me offline and tell me what photos you need and I'll start taking pictures.
Regards
Tony
Tony Bates

Dave,
Thanks for the suggestions--I had thought about putting both heat and cool in the original or modified to be "thicker" Smiths heater box but would have a problem with the evap condensate--basically, how do you get rid of the condensate? That is the reason for using the cold air box.
The Hot Rod Air unit is nice, but this and other units use inside air rather than outside air which results in hearing more fan noise than with outside air--Hence another reason for retaining the present Smiths box. I have been thinking of using a more powerful blower and yesterday found this web site-http://www.frigidair.net which has both evaps that are small enough to make work along with condensors, expansion valves, blowers, etc.
James Johanski

This thread was discussed between 27/08/2003 and 29/08/2003

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