cus

Hello,
I've removed all the a/c from the 350, I've just retro fit an aftermarket heater/demister under the dash. I've connected up the heater hoses, from the control valve to the heater & the hose back to the pump. My old control valve has no vacuum hose connected. I have an in-line on/off valve in the
feed hose that I can cut off flow to the core when I wish. Seem to have restricted flow though, is it because of no vacuum on the control valve?

regards, cus

joe_padavano

It depends on the year and model (which you did not tell us). For the A-body cars, 1972-earlier have normally closed valves that require vacuum to open. 1973-up have normally open valves that require vacuum to close.

For the full size cars, 1970-older have normally closed, 1971-up have normally open.

Of course, if someone installed the wrong valve, all bets are off.

cus

Thanks Joe,
Car is a 1973 Delta 88, valve looks pretty original

joe_padavano

The original valve for a 1973 D88 is normally open and should present no restriction without vacuum applied. Are both hoses to the heater warm when the engine is warmed up?

cus

I investigated more last night, flushed the heater core, hooked up to the manifold,
all was flowing OK, was blocked at the water pump, had calcified a bit in the base of the tube, cleaned out & presto, has been bunged off for quite a few years I think.
Thanks for your help