SS heat exchangers, missing tube?

[EARLY911ZOO]

here's a few shots of the set up on my 73S motor

[EARLY911ZOO]

mmore photos and its about 1" inch O.D. or 26mm

[Allen Henderson]

picture above, the hose outlet for the 72-73 "air regulator" intake is capped off. On the SSIs it is not present. So note that these OEM ones (too bad not stainless) have really an extra sheet metal jacket around the three piper as they come out of the back (front of the car) primary vertical sheet metal heater assembly. Here is a drawing from PET for the 72-73 only left MFI heat exchanger with the intake circled in red. What I did was just run the paper/foil hose down through its hole and leave it open. Some heat would eventually rise up through.
-Allen-

[Neunelfer]

Looks like we found that sparkplug Zookeeper has been looking for!

[blue72s]

The tube that you point out is absolutely essential. It's needed for the warmup regulator on the pump. You have to order the SSI's with the [25mm] tube. Ironically, my CIS T, which doesn't need the tube, has it!

Reviving an old thread but I have question that I think nobody asked before. Factory race cars didn't have any heat exchangers at all, as they had headers instead, so, what alternative source did they use for the warm-up regulator on the MFI pump?

[Arne]

I don't think they had warm-up regulators at all. Or at least not this type. Cold starting is a not a big concern for racing.

[Jim Breazeale]

FYI the picture from Pelican parts is not a SSI heat Exchanger. It is some brand X

[blue72s]

I don't think they had warm-up regulators at all. Or at least not this type. Cold starting is a not a big concern for racing.

So, how did they enrich the mixture for cold starting if there's no warm-up thermostat?

[Arne]

So, how did they enrich the mixture for cold starting if there's no warm-up thermostat?

Any number of possibilities. Small squirt of fuel by hand into the stacks, or a hand operated screw or lever in place of the thermostat. Racing is a totally different scenario, and unlike with a street car there's no expectation that the driver will simply get into a bone-cold car and expect it to start up unattended. So less mechanically complex is better.

[Tom F.]

So, how did they enrich the mixture for cold starting if there's no warm-up thermostat?

Move the rack inside the MFI pump by hand. There is a fitting for this on the back of the pumps for race cars, as I recall.