PRIrish

There have been several threads about upgrading the C3 A/C Heater motor/fan with a C4 unit. My question is will any C4(1984-1996) work or is a specific year required or better? I plan to upgrade my 1976 coupe. Wilcox Corvette has a unit for $73 and I found a 1985 unit at Carquest for $60. Does anyone have a recommendation.

daanbc

Did you do the upgrade? If so how does it work? Thanks..

Easy Mike

You need the C4 squirrel cage and a homemade spacer. Your C3 motor will be fine.

flaco1801

if the c3 motor and the c4 motor are the same speed ( i dont know for fact)..you are better off with the c3 motor because the c4 blower motor has a smaller hole for the cooling fan tube (i had never read that before)..i couldnt get the cooling tube right, luckily i still had the c3 motor and the holes were different, the c4 being too small... i used a step bit to enlarge the diameter of the c4 motor...

alyle5864

I recently replaced by C3 motor with a C4. Motor vent fit fine, bolted right up to the box. I kept the C3 squirrel cage so I did not need the spacer. I used the two wire C4 motor, just have to make sure you correctly wire it up or the fan will rotate backwards.

couperdecar

Last week I went out and bought the upgraded "84 - 86" vette motor/ squirrel cage from NAPA. About $50. Made a spacer out of 7/8 oak I had lying around. Fired it up and I thought my arm was going to be sucked into the vent intake! Unbloody believable how much more air is being moved! I have taken the car out even in -40 weather ( highways have to be clear though) and I've always worn a heavy mits and a toque. I'm thinking with this much air flow - I might be able to just wear a T-shirt !
Hats off to the fellow that discovered this upgrade !

AirborneSilva

I think I'm going to have to do this, how big of a pain is it with the engine in? Wish I would have seen this a month ago when i was doing the engine swap. Also, does the AC dryer get in the way too much? Thanks

thegazman

The improvement is in the fan design for increased air flow, not the motor.

AirborneSilva

can you then put the fan onto a C3 motor?

thegazman

Yes, but you need the spacer. The C-4 fan is longer than the C-3.

AirborneSilva

Roger that, thanks!

couperdecar

Sorry - can't help you there. I don't have AC. The radiator overflow tank has to come off. Reach in behind the passanger front tire, locate the 2 lag bolts that hold it to the inner fender, remove. Next ,locate the 6 bolts that hold the fan motor and squirel cage onto the firewall. Remove. Make a template out of paper. Transfer that paper template onto 7/8" oak. Get yourself some #8 x 1.5" screws and put the new motor / squirel cage with the new spacer you just made back together.
The removal / replace probably took me 10 mins. The spacer took me about an hour.

AirborneSilva

thank you! Somehow I think it will take me a bit longer that an hour and 10 minutes

dgood

before you go and do all that, just get a bigger ground wire to your motor and it will increase the speed of it quite a bit. I went with one gauge bigger and there was a huge difference in air flow. If you don't think this is enough, then go with the c4 setup.

Street Rat

AirborneSilva

Cool guys, adding a larger ground is the easy solution, thanks

couperdecar

I did the ground wire too and it did help some. The REAL answer is the '84-'86 motor. And I thought it'd be a PITA too. Nope. Just a nice little project. At least take your old one off and make a template and work on a spacer. 5 mins to take it off , make a template- 5 mins to put it back on.