1970 911E heat exchangers

[david482]

First thanks to all the good advice on removing the heat exchanges. The MAPP O2 torch did the trick, only one broken stud and it is still protruding about a 1/2 an inch so I think I'll be able to get the stud out.

While removing the HE's to track down an oil leak, I think it is the cooler, I noticed something odd about the HE's. Th PO thought he had put on SS HE's but once I got them off I noticed that the HE itself was SS or some other non corroding material but the connections to the head and to the muffler seem to be steel and at least on the left side corroded. I can move the pipe inside the HE. It does not look like there is any way to fix this but I was wondering if this was a common thing, seems odd to mix SS & steel?

Let em know and I can try and post some pictures.

[randywebb]

I think that was done by some co.s to make a cheap version (knock-off) of the SSI...

[Bill Verburg]

Actually, early on, the heat exchangers were designed w/ mild and ss as a safety feature, SS pipes and mild boxes meant that the outer portion would rust before the inner, preventing an unnoticed ingress for CO gas.

Don't know what you have there but do replace w/ true ss as used in SSI's

[randywebb]

wasn't that in the '60's tho (?)

[Bill Verburg]

right up through at least the early '70s, '72 for sure, maybe '73, the factory didn't start using all ss(still a lower grade outer) til later, probably '75. I know that in '76 it was all ss

The only reason I think '75 was the transition year, was that was the first year of the smog exhausts outside Ca.

[david482]

Thanks for the info. What is strange is that it seems the outside is SS adn the internal tubes steel? Once I get teh oil leak fixed it will be time for new SSi

[Bill Verburg]

It is strange and most likely a cheaper aftermarket exhaust. SSI are a quality product

[randywebb]

Thanks Bill - we probably need a heat exchanger evolution thread..

I may be thinking of the very early "Kill-ya-Dead" design...