View Full Version : 76 Corvette - switch from A/C to heater only

10-31-2006, 11:44 AM
In the near future I'm removing the original small block and installing a 460" big block. Since the A/C hasn't worked in the 14+ years I've owned this car, I decided to keep it that way. What I want to do is completely remove the factory A/C system and in its place install a factory heater only system.

Does anyone know if the factory blower motor and heater box from a non-A/C big block Vette will bolt into a 76 Vette w/ A/C? If yes, any suggestions on sources for these items? Thanks.

10-31-2006, 12:22 PM
First question is what year BB did the heater box come out of? If it came out of a C3 they yes, a none A/C box can be "installed" in a 76 vette. It is not a bolt in operation.

You will have to add fiberglass to the firewall to cover the larger hole left by the A/C box that is not covered by the non A/C heater box. This is not hard at all. It is VERY easy if you can find a junk non A/C car and cut the piece from the firewall that you need. Finding a C3 hull should not be hard as there are junk non A/C C3 hulls everywhere! You can also make a fiberglass filler to glass in the firewall if a donor hull is not available. I have converted numerous C2 non A/C cars to factory A/C and vice versa. It's real easy when they are sitting side by side and you swap the parts and cut the firewalls.

Complete C3 heater boxes (inner box, firewall cover, ducts and cables) are not hard to find. Try any of the larger/smaller Corvette used parts vendors. Expect to pay $250 for a complete box with cables. You will also need to find a non A/C metal shifter console, vent cover by the wiper switch and roller heater/defroster control as they are also different than an A/C car.

Personally, I would make the A/C work. Between buying the none A/C parts and your labor, making the A/C work will be cheaper and make your car much more desireable and fun to drive. You will de-value your Corvette by removing the factory A/C. You will also loose half or more of the potential buyer's whenever you decide to sell your now "non A/C 1976 Corvette" car as 76 model Corvettes are hot inside the car with out A/C.

Non A/C Corvettes were made in 1976 and they are hard as hell to sell. Think hard about this before you make the switch!

10-31-2006, 03:37 PM
You make valid points about keeping the A/C Mike. Since I've never owned a big block C3, my biggest reason for wanting to delete the A/C is to make it easier on me when it comes to work on the engine. so here's another question... How much of a pain will it be to work on the big block if I keep the A/C in place?

10-31-2006, 08:17 PM
Actually not bad at all! You can change spark plugs on a BB C3 in about 20 minutes. The A/C compressor makes for extra work when removing the valve cover and makes tall valve covers difficult to install. Make sure you keep the power steering as C3's with BB are a bitch to steer without PS.

While headers are nice, they add a lot of heat to the engine compartment and I have yet to see a set that did not require "massaging" on the left side header to get them to clear the steering box. The original BB manifolds flow very well and are now CHEAP if you buy the China non dated repops. I saw them for $280 a set at the last show!

Just remember that everything is different for a BB. That includes the radiator support, radiator, fan shroud, A/C brackets, hoses, fuel line, lower pulleys, PS and Alt brackets etc. All easily overcome but something to consider none the less.

Good luck with your project!

11-02-2006, 10:10 AM
One last question, hopefully you can answer. Since keeping the A/C is probably a better idea than removing it, is it possible to run a Sanden A/C compressor with the factory Vette A/C system if I were to use a Vintage Air Front Runner?

11-02-2006, 02:58 PM

I'm doing a similar swap in my 79 Z28. 509 BBC with VA Frontrunner setup onto factory a/c.

You'll need new lines made up, change out the accumulator and change over the orifice tube to a F*rd blue one, and change the condensor to a new style parallel flow unit. Should cool well, and that's what I'm doing with mine. Make sure that you thoroughly flush the evaporator, and the condenser if you keep it. A good, competent, a/c shop should be able to this without much trouble.

The nice thing about keeping factory air: It uses outside fresh air, nearly all the aftermarket ones are recirculating. Kinda defeats the purpose of having a/c if you have to crank the window open once in a while just to get some air...


11-04-2006, 06:06 AM
Getting new lines made shouldn't be a big deal and I'll most likely replace most of the A/C parts in the process. The thing that concerns me is the Vette system has a unique valve of some sort that I heard won't work with the Sanden style compressors. I guess I'll worry about that bridge when I get to it.

11-05-2006, 08:26 AM
Yes, you can run a Sanden in a C3. The valve you are talking about, is that the POA valve? If so you switch that out for 134A anyway or you can. Old Air products sells a replacement as does Hot Rod and Vintage. The VIR valve which is what should be on the 76 works with 134A and should work for the Sanden. If not, that can be worked around as well.

I would keep AC on the car. Mike is right, it is not hard to work on a BB in a C3. As for headers, we have Hooker Super Comps on a 71 BB car at the shop. No problems on the left side around the steering box, but the right side by the idler arm needed a denting to fit right. Some cars need clearencing on that side while others don't. Getting the headers in is a breeze from underneath even with this car being a four speed and still having the old Zbar clutch linkage.

11-05-2006, 01:30 PM
My 76 is an early model and according to the info I've read, it should have a POA valve. It sounds like it should be a fairly simple project then to switch to 134 and a Sanden compressor. That makes me happy. Thanks for the info Trey.

11-05-2006, 05:08 PM
Vintage Air now has a new sure fit kit for '68-76 Corvettes. There are kits for factory air and non air cars. The kit removes the large evaporator box from the firewall.

11-07-2006, 06:01 AM
No problem. The one thing you may want to check on is with the condensor. I put a brand new Delco condensor for a 76 on the front of this car that was converted to 134 and I have run 134 through a 69's stock condensor. I had no problems, but the local AC guy says it will work better to use a hiflow consendor. I haven't had to do anymore AC work so I haven't called vintage or Hot Rod to verify if that is correct.

11-07-2006, 07:08 AM
Kul Fir Chick N - I checked Vintage's web page but couldn't find any info on a new system for my year. Maybe they haven't updated their page yet. I have a Vintage system in my El Camino and though the A/C part works great, the heater leaves a lot to be desired. I asked Vintage about that and they said the system is primarily for A/C and the heater is pretty much just there. Before I go through the expense of changing my Vette to a Vintage system, I think I'm going to try the factory system and update it with newer components because I need to have a good heater in my car, I'm originally from AZ afterall!

Trey - Now that I think about it, when I talked with Vintage (a long time ago) regarding using newer components, I vaguely remember something about the stock condensor not being correct for the Sanden compressor. I think that's all the info I need for now. Before I even get to this part I have to finish getting my Blazer on the road and then get the heads for the big block. So much to do and so little money to do it with!

11-07-2006, 05:43 PM
Its a new kit and it is in our new catalog and on the website at this link:


The tech you spoke to was partially correct. We do put the emphasis on A/C performance, and some of our earlier kits (your El Camino is one of them) had less heat capacity than the later ones. Nevertheless, you should have plenty of heat from that system. There are several factors to consider when the heater is not performing.

1. Be sure the heater valve is properly adjusted. You need to be able to shut it all the way off, but no more; make sure you use the full stroke of the lever to open the valve.

2. In order for the heater to work properly, you need good flow through the core. The only thing that pushes coolant through your heater is the back pressure created by the thermostat and radiator. You must have a thermostat installed, and a thick, low restriction radiator will have little back pressure, especially at idle. Underdrive pulleys will reduce the flow at idle even more.

3. Be sure the car is sealed up. Just like with A/C, if your door seals leak, or you have cold air coming in around your shifter, the heater will have a hard time keeping up.

As for the 'Vette system, it is our newest "Gen 4 " system, which uses the most efficient heater core available anywhere. It is small, but it packs a punch. I think you would be quite happy with the system.

If you choose to hop up your stock system, the first thing I would do is install a heavy duty fan clutch and fan. In addition, I would install an electric fan to the front of the condenser, and seal up any gaps around the shroud. The main problem with vette systems, including engine cooling, is getting air through the condenser and radiator since it is canted and air doesn't have and good way to get into the radiator or out of the engine bay. If the stock condenser is not beat up, or leaking, I would flush it and re-use it.

Hope this helps,


11-07-2006, 05:44 PM
yeah I know the feeling about being low on cash. I am back in school now and have nothing to spend on the car really. Good luck with it all.

After reading Ryans post, might I suggest a radiator and dual fan kit from DeWitts. He offers a drop in replacement aluminum radiator with twin 11" spal fans. This system works fantastically well. I put one in the 76 I built and on the dyno doing multiple runs it would cycle the fans with a 180* switch. Simple heads cam SBC. Only caution I can give is that the fans are loud. I don't mind but they are easily heard.

11-08-2006, 09:01 AM
Ryan, thanks for the info. My El isn't used as a regular driver so the low heat isn't too big a deal for me, however, my wife complains about it. I'll check the heater valve as you mention but just so you know, I'm not running a thermostat. I know, I know everyone says it will run cooler with one, but in my case it doesn't. Even though there's no thermostat, the coolant flow is restricted by the A/N upper rad hose being a -16 and the manifold fitting has a fairly small opening. In the summer with the a/c running my engine temps are in the 170-180 range. Running around in the current climate the engine temps get as low as 140 on the highway. That's part of the reason I don't drive it much when it's cold out.

Anyway, back to the Vette. I truly like the idea of getting the factory a/c box off the firewall so I'll have to check out the new system you have. That might be the best way for me to go. I have to check out the link you provided, thanks. As for the cooling system on the Vette, it's good enough for now, but when the new 460 goes in, it will be completely revamped with better parts.

Trey, I feel your pain but since I'm not in school, probably not as bad! As for the radiator recommendation, I've become very happy using Ron Davis Racing radiators in my cars. The El has one with twin Spal fans and my Blazer also has one with twin Spals. Naturally, the Vette will get one when the time comes, but due to the space limitations between the upper control arms, Ron Davis uses a single MK IV fan on that application. I'm not sure what its diameter is, but it's a pretty good size fan. I can post of pic when I get home if you're interested. I've noticed that a lot of aluminum rad companies use plastic fan shrouds that clamp onto the rad in some fashion or other. Ron Davis makes custom aluminum shrouds that are integrated into the rad's design. Not only do the work great, they look killer too!

On the El the exhaust noise drowns out the fans, but they are easliy heard on the Blazer. The Vette will fall somewhere in between the two.

11-08-2006, 04:20 PM
The twin 11in spal fans have their own shroud. They take up 90% of the raidator and easily fit in front of the upper control arms. DeWitts welds on a bracket to the top and bottom and bolts the fan to those brackets.

I have heard good things about the Davis radiators. My biggest deal with DeWitts is that his radiators are specifically designed to work in the Corvette with no modifications at all. I could drop his aluminum radiator into a factory shroud and it would fit no problem and be nearly twice as thick.

Definetly go with what you like especially if it has served you well in the past.

11-08-2006, 07:37 PM
Here's the picture of the Ron Davis radiator for the Vette. I know what you mean about being able to drop it right in. When I first bought the Blazer it needed a new rad so I figured the quickest thing to do was to order a Be Cool from Summit and swap it in and be on my way. It turned out that the Be Cool used the wrong size core and the saddles on the core support didn't line up with the tanks properly. I should have known better and ended up returning it to Summit and ordering the full deal from Ron Davis. After a long 3 week or so wait it showed up on my door step and fell right into place as promised! I'm sold on Ron Davis regardless of price.

11-08-2006, 07:44 PM
Back to the a/c topic. Ryan, I looked over the info on the link you provided. I like the fact that the original controls are used for the new system. How much is the complete kit going for and if I went with the Frontrunner setup, would the prices be able to be adjusted since I wouldn't need two compressors, etc? I'm just curious right now since that step is still a bit down the road. Thanks.

11-09-2006, 05:11 AM
I'm not in sales, I'm in engineering, but I believe the complete kit is around $1200. Yes, the price would be adjusted for the Front Runner, but you would also need to make a couple of custom hoses since the Sure Fit hoses are set up for the standard bracket and compressor. Still, the two custom hoses would be a very simple deal.

11-09-2006, 08:51 AM
That sounds reasonable enough. Once I get the small block out and get everything cleaned up, I might go this route instead of trying to mix and match new age components with a 30 yr old system. Thanks for your time and info Ryan.