old style heater block off question

[twobone]

My 89' crossflow has the old style large black box heater. With one pipe going in on the exhaust side and out on the carb side.

I've tried blocking the air vents in the cabin, but the heat still comes through.

I'm now thinking of installing a basic ball valve on the inlet side to turn off the hot water to heater flow.

Am I correct, that this will not harm the engine cooling flow?

Is this the same function as the old heater cut off valve?

[BDA]

Two bone,
Yes it is fine to install a valve, caterham used a VW part with a choke type cable under the dash to operate.

Cheers
Chris

[twobone]

Which side to I install it on? I assume on the hose that leads from the higher side of the engine.

Thanks

[BDA]

Twobone,
install the valve in the pipe running from the inlet manifold to the heater.

cheers
Chris