Hello all,
Forgive me if this has been asked already. I've recently acquired a set of heat exchangers from a popular auction site that were described as "little used, 1.7/1.8 heat exchangers". I got them for a steal. Upon receiving them, I realized they had very little rust, and we're in great condition. And by little rust, I mean no rust except for the muffler flanges which had little to moderate rust (looks like it may have been leaking for a while) The shrouds were "shiny" as if they were made of aluminum? And the headers are discolored with maybe light surface rust or something? Definately something a little polish or scouring pad could clean and make shiny again.  I checked it with a fridge magnet and the shroud was non-ferrous, and the headers barely if anything had any magnetism. Have I stumbled upon a set of well-used stainless heat exchangers or just a damn good set of originals? Is there a better tell like a stamping or something?

Sounds like SS to me.

Well, that's kinda how I'm leaning, except the muffler flanges are fooling with me.  I thought SS HE had SS muffler flanges. These flanges, although I didn't check them with he magnet, are fairly rusty.

The early production models had mild steel flanges. I don't know why (call John at SSI, ask him, and then tell him he should sell the molds to Mark Whitesell so Mark we can have new ones made).

I think Mark Bland (Engman) sells SS replacements you can have welded on.

Interesting...I might have to give him a call. In the meantime, this is what I got, and what I took off the car last winter.Click to view attachment

Click to view attachment

Click to view attachment

Yepp, they look like early SSI exchangers that had the mild steel flanges. As McMark suggested, someone here makes a SS replacement for those rusted flanges.

Nice find!

Now, go and read the thread about how they can crack inside and leak CO into the cabin. There was a big discussion here a few weeks ago with some tips on how to test them for leaks.

I got a set of early SSIs on the evil-bay myself, no/little magnetism on the body, sticks on the mild steel flanges.

Yes it's Engman on here who sells the SS flanges if you want to replace them - or you can just clean up the rust, true-up the flange mating surfaces, prime & paint. I got those too & IIRC they were about $40-50 for a pair.

Wow. That's amazing! Thanks everyone for the help and advice. I'll have to track down the thread about testing them for sure! If the flanges aren't cracked (haven't really looked hard) I may just do as suggested and true up the flanges and treat/seal em. Thanks again everyone for the help!

Nice score. Funny thing, the last two 914s I bought both came with SS HEs.

Next Q: Are all SS HEs aftermarket or did some come from the factory? If the former, it's amazing how lucky we got.

My question still stands: is there any way to verify HE's are SS in the wild? Did the mfgr stamp anywhere, or is the magnet check the only way to know?

They are all aftermarket. No markings that i know of.
The lack of rust and the magnet test should do the trick.


And to add to the confusion, sometimes people (wrongfully) refer to the late model '75/'76 exchangers as SSIs.

SSI never made heat exchangers for the late model cars as the '75 and later exhaust system is of a completely different design.

SSIs are a specific brand, correct? How many brands of SS HEs are there? Any tips on identifying SSIs vs others?

SSI is the name of the company. They're located in Novato, CA. John, the owner, has a 914/6 with the elusive factory m471 option.

Anyways, i am not aware of any other stainless steel exchangers besides the SSIs.

It's a pretty safe bet that if you see shiny or silver metal, they are SSI (the only SS heat exchangers). If you see black or rusty, they're stock. Late model 180° exhaust excluded.

Hey Mark, since they are SS, should they be ceramic or other material coated or are they fine the way they are?

These are the real deal full stainless ones with stainless flanges

I had looked at making these. I have the equipment to make the Header portion no problem. The issue has been the clamshells that are part of the heating system. I had spoke with John at one time about doing a group buy, but he wasn't real interested it setting up to do these at the time. Honestly, if we could do a group buy, that may be the way to go. If these is some interest I will try to work with him to see if something can be put together.

I'm interested in participating in a group buy for a new set of 2.0 SSI heat exchangers. I'm curious to find out what kind of deal we could get. It seems it's been a few years since John produced SSI heat exchangers. I believe there is now enough demand for replacements that it would be worth his while to produce another hundred sets or so.