I'm looking at a set of SSI or 1974 heat exchangers for my 75 911S and was wondering what the small tube at the heat flapper end is connected too. Also what else will I need to backdate to 1974 exchangers or SSIs? Is there a special oil line that's not on the '75?

Jack

 

Not all SSI have that tube, it is for the preheater on MFI cars. Block it off if your car doesn't have MFI

 

Jack: Is your car fitted with thermal reactors? EGR (exhaust gas recirculation)? Smog pump?

Pete

 

Peter,
Luckily I have none of that stuff and wanted to go to the 1974 or SSI set up to gain a little horse power on my 2.7 that I in the midst of rebuiling in the stock configuration. I'm also changing to a 1974 915 tranny with the 7:31 R&P.

Jack

 

Jack: Check the length of your exhaust port studs. If I remember correctly they will be much too long for use with the thin flanges on SSI/'74 heat exchangers. If the heads haven't been done yet have the stock studs removed by the machine shop and put in a set of short ones that won't require spacers/washers. Thermal reactor cars had thick flanges and very long studs that were tapered in the middle, almost as though they had a narrow waist. I can't remember if 49 states cars used the same studs, but check them while replacement is easy!
Pete

 

'75 uses then flange and yes there are a couple of oil lines needed, which ones depend on whether or not a front cooler is on the car.

In this pic you can see most of what you will need, this is thicjk flange though