Introduction and MFI engine intake question

[NorthernThrux]

Hi everyone,

New to the board and new to 911s. Have a deposit on a tangerine 1972 911T that is almost pristine except for a partial (well done) respray. 2 owners, every receipt since Dec. 1971. I've been searching for a good car for a couple of years (and watched the prices climb during that time - wow, talk about getting on the bandwagon). The car I want should be perfect enough to be a weekend driver and not rust before I can attend to any restoration after I retire (which is 15 years out). I think I found it.

My father had a 901 Porsche on order, which he transferred to another colleague when my mother informed him of my sister's conception. So he cancelled that order, sold his 55 Beetle that he currently had and bought a 64 Impala. Sigh. I'm going to right that wrong ! He is 85 and would love to have that 911 ride, even if the '72 is a bit later than that first car.

There is one detail on the car that I have my eye on that I can't get my head around and I'd like people's help on. As with a number of MFI cars, I've seen the intake tube into the airbox abbreviated. See the actual engine in the pic. It appears to be missing the intake hose that goes to a box on the driver's side of the car which either takes in warm air through a corrugated metal hose, or allows a direct air intake. I assume this is some kind of warm air intake. I had something similar on my 1980 Saab 900 Turbo which has Bosch K-Jetronic and there was a thermostatically operated diverter valve in that box.

So my question is, is this missing, or did some cars not have it ? And if it's missing, I can imagine that gives cold start issues in cooler climates, at least during the shoulder seasons. Is it easy to source/replace ? I'm very mechanically minded, having rebuilt the engine and CIS system on that old Saab, as well as numerous motorcycle engines, so I'm not afraid to take projects on. But I do prefer some sage advice before I do !


I should say that the exhaust is original, and not an SSI, so there is no reason in theory for this delete. But I have read elsewhere that Porsche issued a TSB at some point saying the thermovalve wasn't necessary, so people yanked it. But lots of cars still have it, so I'm not sure on the validity of that rumour.

[RSTarga]

All the 72/73 2.4 and 2.7 engines with MFI had the same thermovalve. To my knowledge it has nothing to do with the warmup of the engine, that is done by the other smaller diameter flex hose coming from the exhaust to the MFI pump. This hose should be kept in place.
The thermovalve was more for emissions, providing warmer air quicker to help combustion in some way.
Most of us have long ago removed it as it just gets in the way, (my excuse).
Nice looking car.

[NorthernThrux]

Thanks for the response. Yes, I bet you are right. I now have a vague recollection that this was the statement in my old Haynes manual for my Saab. That started at -40C without the thermovalve, so it can't be a drivability issue in retrospect.
I'm a bit torn in that it is nice to have the car "correct", but on the other hand, who wants the extra junk if it doesn't do anything. I have solar hot water panel on my house, so I'm doing my part to reduce my carbon emissions. Everything is a balance !

[M_deJong]

In the picture the warm up hose to the MFI pump is missing too. You should fix that.

[NorthernThrux]

This is the hose that goes from the L/H heat exchanger to the thermostat assembly on the pump ? I believe (but will check), it was removed for cleaning.

[M_deJong]

yes that's the one... I can see the fitting just above the coil in the picture. There was some discussion recently on the proper way to attach this hose, worth a search.

[mobius911]

That's the one with a paper, smaller diameter inner hose and a separate outer plastic sheath hose, presumably for thermal insulation. I've tried different approaches and the one I prefer is to clamp just the paper hose, and let the plastic one ride loose on the outside. If you try to clamp that one too it just never works right. At least for me!

[Alan.uk]

Just in case a picture helps. Here is a 73 motor we detailed.



Thanks

Alan

[72targa]

Make sure to post pics of that ride with your Dad!

[RSTarga]

here is a picture without the thermovalve so you can see the smaller hose we are talking about