In the restoration of my '71 Chevelle into a Pro Touring car, I chose to install a Vintage Air aftermarket A/C & Heater setup. There is a 4-port bulkhead on the smoothed firewall, 2 A/C hoses and 2 heater hoses. In an attempt to make the "look" of the four lines connect at the bulkhead, I tried to use A/C fittings crimped onto rubber heater hoses. During engine start up this weekend, water started shooting out of my experimental crimping job...so it looks like that will not work. I do not want to just use hose clamps at that location, it would defeat the esthetic goals.

My A/C system has several different size hoses, the largest being #10 with a 1/2" inside diameter. The #10 hose fittings are the same ones used to connect the heater hoses to the firewall bulkhead.

MY QUESTION: Can anyone tell me if using heater hoses with a 1/2" inner diameter (they're usually 5/8" I.D.) will pose any issues in the coolant system? If not, I can simply use more of the #10 A/C hoses and crimp fittings to route my heater hoses.

Please let me know what you think. Thanks!

I don't see any problems with the cooling system other than your heater may not be as efficient.