Gap in heat exchanger tin typical?

[logician]

Hi,

In looking at the heat exchangers my '73 911, I find that there is a pretty big gap ~1/8" between the exhaust pipes and the heat exchanger tin, all the way around the three exhaust pipes where the tin meets the pipes. This seems pretty inefficient for heating. Is this pretty typical for '73 vintage?

-Juan

[Jim Sims]

I just went out and looked at some old OEM units that came off a '73 and they have the same gap you report. The new SSI's which replaced them have a much tighter fit to a sleeve like cuff on the tin of the outer jacket. The OEM unit leaks some air but cheaper to manufacture (looser tolerances) and no concern about differential thermal expansion over stressing the joints. Cheers, Jim

[logician]

Hi Jim,

Thanks for the info!

-Juan

[john walker's workshop]

good ones fit the pipes snuggly. that's heat loss there.

[Doug Zielke]

While we're on the subject.....
I was told (warned?) just how much additional heat SSI's would provide.
Well, kids...it's *true*. The cockpit is toasty-warm now like never before, and the heat comes on almost instantly.
And this is with the back-dated heating system (no more electric blower), I installed when the motor was out.

[john70t]

Hey Doug-still got that fan or know of a source for it? Thanks