SS heat exchangers, missing tube?

[Zithlord]

This 71S engine was sometime in the past converted to carbs. After a good cleaning, painting parts, new valve covers, gaskets etc, the MFI are going back on(thanks to Eric and Supertec!). What I noticed after removing the engine was that there is no tube on the left heat exchanger, I have marked the spot where I have seen the tube with a red cross on the picture, in the parts manual. Is the missing tube supposed to have a hose attached that go up to the engine tin and then to the MFI for pre-heating or something? Do I need this tube? If so is it possible to weld on a tube to Stainless steel?

Thanks
John

[Allen Henderson]

John,

The SSIs don't have the tube. I warm climes, that is not a problem. Could be, though, a suppose up near (er) the artic circle. Edit: I was wrong on this, see below

-Allen-

[Zithlord]

Hi Allen

I see in this picture from Dansk that the left one has the tube, but as I understand you I dont need that tube as my car will be started in a heated garage and driven spring and summertime. Should I just use the hose from the MFI down to the engine tin and leave it with that?

John

[Tom F.]

John,

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 tube. Ironically, my CIS T, which doesn't need the tube, has it!

The tube that SSI omitted was the intake air preheater, as seen on the 2.4 MFI cars and the 911/83 Carrera motor. To my knowledge, SSI never offered it, and actually recommended against it, supposedly because it takes up road dirt into the intake air stream.

I'll go to USPS tomorrow. Sorry for the lost day, but I had to work at my day job.

Tom

[jashford]

The tube you are missing provides air via hoses to the injection pump. As the car warms up, the hot air passes through the warm-up thermostat which leans out the pump to its desired hot operating mixture.

Best, John

John Ashford
Towson, MD

[Allen Henderson]

about 12 years ago, when I rebuilt my 72S the exchangers with a tube was not avialable. If it is now, that's great! I do recall though, that there is a large opening/tube that goes up to the air intake box and that THAT is missing from the SSIs and not available.

-Allen-

[gulf908]

John,
I am not an SSI / MFI expert but here's what I have in pics.
The first shows the warm air outlet - circled - to go to the MFI pump warmup regulator.I got this pic from either here or Pelican for reference such as this.
The second is from my car after installation of the SSIs - sorry about the dirt,chaps ,but it is my only driver and we have serious water restrictions here !
The horizontal black pipe comes from the SSI h/e and goes through the tinwear up to the MFI pump via the double paper / foil pipes.
+ 1 on jashford's operating description - if you do not have this system in place,you are just throwing gas straight out the exhaust pipe !
Can't help with the welding question,though.

HTH,
Dennis.

[Zithlord]

Thanks a lot guys. I will try to have a bent tube welded on. My SS H.A. are probably an early model without the tube, and new ones are too expencive. One more question; dos the MFI tube/pipe go through the wall of the larger tube that goes to the flapper box and have its own internal piping(inside the heat exchanger), or dos it share the same air as the large tube for the flapper box?

John

[Tom F.]

John, It just penetrates and inch or two into the large pipe that supplies cabin heating air. By the way, it is important to keep the hot air hot all the way to the MFI pump warmup regulator. This is best accomplished with a very thick wall rubber hose from the heat exchanger to the transition pipe through the engine sheet metal , and then double paper tubes, one inside the other, from the transition pipe to the warm up regulator. These are the parts that Porsche supplied, at least as of four or five years ago. The idea is to insulate the warm air supply to the warm up regulator from cold ambient air.

[Zithlord]

Perfect Tom!

Correct hoses are ordered from Pelican. I just talked with a shop with special equipment to weld stainless steel. They will weld in the missing tube, no problem at all. Do any of you guys know the correct diameter of the metal tube, for the rubber hose, exiting the heat exchanger?

John