Sudden LOUD Valve Train Noise Options

[relentless]

Coming back from a trip to the coast, there was a sudden change in the sound of the motor, a 2.0L of 1976 vintage. Well the first thought that came to mind was that one of the heat exchangers had come loose, which seemed strange. The noise seemed to be coming from the passenger side, and it sounded like the valves were six inches behind me, on top of the motor. Every time I pressed on the gas pedal the valve train racket got LOUD, and as I coasted the car sounded like it should.

When I got home I raised the back of the car, took off the covers for the heat exchangers, and checked the exhaust manifold nuts for tightness. They were tight, and there was no play between the head and heat exchanger header.

So I ordered new copper exhaust gaskets (and new nuts) thinking that maybe I had a leaky gasket. The new parts arrived today so I removed the passenger side heat exchanger and to be honest, there didn't look like any leakage between the header pipe, gasket, and head.

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I annealed the new copper head gaskets and went to install them. They kept falling out, so I ended up using some RTV silicone seal to act as a glue. I coated the gasket on one side and slid it up into the head, and was relieved when the gasket stayed in place while I carefully slid the heat exchanger in place.

I torqued the new header nuts to 15 ft-lb, tightening them first to 10, then 13, and finally 15. When I ordered these nuts and gaskets I asked Dave Darling which parts to order from Pelican, as when I did a search on the site the gaskets referenced 911 and 1.8L but no mention of 1.7 or 2.0. There also weren't any exhaust stud nuts coming up when I did a search.

Well Dave pointed me to Glenn Sager, x240 at Pelican, and after speaking to him I ordered the 039-256-251-m17 gaskets. Glenn also said that there was a BMW exhaust stud nut, copper coated, that would work. I believe the P/N was 18307620549. These nuts are a lot cheaper than the Porsche part and fit well.
I did put some copper anti-seieze on the exhaust studs as they were getting a bit rough looking and had originally been put in 'dry.'

I started the car and immediately knew that the exhaust seals weren't the problem. I had read about some noise problems that were due to the air injection components of the 2.0L 914, so I began tugging on the metal lines. Here is what I discovered:

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Not only had the metal tube on the passenger side broken off, but the mount over the air intake tubes had also broken off. The breaks were not visible and the LOUD valve train noise didn't need much of a gap to sound like there was no exhaust on the car!

I had a lot of rust on the couplers, so I have sprayed them with penetrating oil and will be welding or brazing the parts back together shortly.

While thinking about the LOUD valve train noise I did some searches out here on 914World, and some of them mentioned the air injection circuit as a possible culprit. I hope that this helps some 914 enthusiast out in the future!