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Join Date: Jun 2001
Location: St. Louis Missouri
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More 73 heat exchanger questions
My car failed inspection due to leaking exhaust - holes in the heat exchangers. The inspection was last August and I can now fix it.
I don't hear any leaking exhaust noise. I think the problem is just the exterior of the exchangers. The mechanic has a left or right single SSI for sale - I'm not sure which yet. Pelican says they cannot split sets (I can't purchase just the left or just the right) so I am trying to figure out if both of mine are bad. One of the heat exchangers had a patch job; the patch was detaching so I pulled it off. My question is about the difference between the two sides. LEFT has a muffler outlet, and two other outlets. The left has an extra shell around the three pipes where they combine into one for the exhaust and this shell has an unattached opening.  RIGHT has a muffler outlet and one other outlet.  SSIs don't appear to have the extra Left shell and outlet. Left and Right SSI look like mirror images of each other. Is that extra shell and outlet on my left necessary? Also, here is detail on the Right. Would this leak? 
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06-12-2014, 10:52 AM
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Location: Santa Maria, CA
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The left heat exchanger for 1972 and 1973 cars equipped with MFI has a port near the heater outlet for the heat riser to the MFI pump, as well as a larger outlet for the heat riser to the hot air box for the air filter. The first is for an adjuster on the back of the pump that alters the mixture as the engine warms up, kind of like a choke. The second one is used to provide warm air to the air filter during warmup, and is a mechanism that's pretty common industry-wide. The emissions books refer to this as a "thermostatic air cleaner". You can live without the second one, but not the first, unless you've done a manual workaround for the temperature compensator (thermostat) on the FI pump.
The Cap'n |
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06-12-2014, 11:20 AM
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The car has Webers now so I'm not worried about the MFI port.
What I am talking about is the extra shell and large outlet on the left heat exchanger that is not on the right, and is not apparently on the SSIs either. |
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06-12-2014, 12:27 PM
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The large outlet is the one you can do without. I suggest plugging the smaller outlet with something that can be reversed. That high end shiny silver duct tape (NOT the everyday gray stuff!) should do it. A couple of layers at right angles and a hose clamp.
The Cap'n |
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06-12-2014, 01:20 PM
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Heat exchangers successfully removed!
 What is the circled part here? I don't see it on any of the SSIs. 
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06-13-2014, 10:41 AM
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That connects via a hose to the air intake flapper control unit on mfi cars which some take out as it pretty much does nothing. Kind of like a pre-warm up device that was supposed to help with emissions.
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72 911 Although it is done at the moment, it will never be finished. Last edited by tobluforu; 06-13-2014 at 11:08 AM.. |
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06-13-2014, 11:06 AM
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thank you!
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06-13-2014, 11:10 AM
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Two or three of the studs came out with the nuts.
The Pelican catalog lists the studs. Should I replace all 12? Should the studs come out of the cylinder head easily? I am kind of paranoid about breaking them off. The ones in there look okay. The engine was rebuilt about 30,000 miles ago. |
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06-13-2014, 12:58 PM
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Quote:
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72 911 Although it is done at the moment, it will never be finished. |
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06-13-2014, 01:05 PM
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Just to be clear. The sheet metal around the exh. pipes contain only ambient heated air from the cooling system, not exhaust gases which are inside the individual tubes.
Did the smog tech conclude from a visual inspection that exhaust gases were leaking from the holes in the HE sheet metal or did he sample that area with a CO sniffer? No telling the skill level of various techs. Sherwood |
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06-13-2014, 01:53 PM
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You want to seal test them so the exhaust does not leak into the heat exchanger as it will pump co into the cabin when you use the heat flapper
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06-13-2014, 03:02 PM
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| Tags |
| early , heat exchangers , ssi |
Tobluforu
