1972 911T Heat Exchanger Question

[LeeD]

I am in the process of replacing my heat exchangers on my 1972 911 T with MFI. I am planning on going with SSI 91 913 and had a question about the preheat connector on the heat exchanger. Circled in RED in the attached picture.

Is it best to have it cut off and if I cut it off, will I need to block it off? Or should it just get blocked off? What would be the best way get it cut off and blocked or just blocked?

[edmayo]

Just go to the hardware store and find a cap or plug to close it off, no need to cut anything.

[gled49]

Mid year 73 intake pre-heat pathway was changed from under the engine to going thru the 1-2-3 side sheet metal to get clean air from the engine compartment. Picture shows new side sheet metal piece which connected to your style heat exchangers with a foil hose.

[Bashbell]

Don’t want to hijack this but I have a 72 911T with Oilkappe and these very ssi heat exchangers . There are two hose connectors on the exchanger . One circled red and one top left next to the hot air exit . Which of these is for the preheat into the mfi and what’s the other one for . Any help / enlightenment is appreciated.
Dave

[NorthernThrux]

Green circle is the large black hose that comes from the fan shroud, through a hole in the engine tin. It pressurizes the heat exchanger and sends air to the MFI warm up and the cabin.
White circle is the so called "steam hose" that goes to the engine tin stub in the picture Gordon posted, and from there the double walled paper/foil hose takes it to the MFI warmup regulator.
Red is not connected. It is the inlet for the warmup function on the flapper box. Outside air goes in through the red opening, gets warmed up, exits through the blue circle and through a large foil hose to the flapper box. This circuit is only active at warmup. The warm air heats a thermostat in the flapper box which slowly closes a flap and then the air is drawn only from the engine compartment inlet to that flapper.

I cut a small piece of stainless window screen material and popped it into the red inlet to prevent road debris from being hoovered into the airbox. I think there is another screen at the flapper box, but that's my belt and suspenders approach.

For a '73. YMMV.

Ravi