Will These Exhaust Ports Seal? Options

[frank_c]

Hello,
I acquired a '76 914 2.0 a little over a month ago. The car had the original '76 exhaust system on it, and as part of many repairs & changes I have made so far, I swapped out the original exhaust with a set of new SSI heat exchangers and a MittelMotor muffler. Note that the original exhaust had what I suspected was a small exhaust leak as the engine would backfire a few seconds after every shutdown.

After the exhaust swap (with new copper gaskets), I took the car for a quick test run and it backfired excessively. At first, I thought maybe one of the gaskets became dislodged when I was fitting the HEs, but when I pulled the HEs all the gaskets were in place. Upon further inspection, the leak appears to be coming from cylinder 3. Photo 1 shows Cyl 3 before I removed the copper gasket with signs of the gasket not sealing at the bottom of the port.

Photo 1:



I confirmed that the new SSI HE tubes were flat and parallel where they mated to the head (photo 2).

Photo 2:



I removed all the gaskets and cleaned the gasket mating surface of all the ports to inspect the heads for damage.

Photo 3 shows the Cyl 3 port. It's not easy to see in the photo, but there is a slight indentation in the bottom of the mating surface that corresponds to where the black mark is on the head from the leak. Photo 4 shows the indentation a little better.

Photo 3:


Photo 4:



On Cyl 4, I noticed that the port has a strange step in the mating surface at the top of photo 5, but it appears to be sealing ok.

Photo 5:



The ports on Cyl 1 & 2 look good.

So here's my question - do you think that if I were to anneal the gaskets, and use high-temp copper RTV, that I can get Cylinders 3 & 4 to seal given the non-perfect mating surface on the head? Or does the cyl 3/4 head need to be repaired? Note that I did not anneal the gaskets previously, and only used some grease to hold them in place when fitting the HEs.

Thanks for any advice,
Frank