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

[TheCabinetmaker]

Did you anneal the copper gaskets?

[73-914]

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

You HAVE to anneal copper gaskets (IMG:style_emoticons/default/smash.gif)

[frank_c]

Ok, thanks for confirming that the annealing process is critical for getting the gaskets to seal properly. In my initial reading several weeks ago on installing HEs, the annealing was mentioned by some, but not all. Upon further reading since then, the consensus is clearly that annealing is the way to go (along with some type of sealant).

With the annealed gasket and High Temp RTV (Permatex 81878), does this damaged seat area circled in the photo below have a good chance of sealing? I suppose there is one way to find out..

[Montreal914]

High temp RTV??? (IMG:style_emoticons/default/blink.gif)

[barefoot]

I think you'll have sealing problems with the ports in that condition.
Put a thin layer of Prussian blue or grease on a good copper gasket and hand press it into the port, then look to see if blueing or grease has left a full impression in the port, if not you need to have some work done to true them up.

Good luck (IMG:style_emoticons/default/sunglasses.gif)
Barefoot

[bkrantz]

High temp RTV??? (IMG:style_emoticons/default/blink.gif)

Be gone, satan!

[Superhawk996]

High temp RTV??? (IMG:style_emoticons/default/blink.gif)

Be gone, satan!

(IMG:style_emoticons/default/lol-2.gif)

On a more serious note, try the annealed seals. If that doesn’t cut it you are going to be looking at some machine work to flatten those ports that look to have been damaged by someone prior. (IMG:style_emoticons/default/headbang.gif)

[rhodyguy]

Tighten the nuts in an X pattern and in stages increasing the torque values. Tightening one nut fully while the others are loose, is a pretty good way of building in a leak right from the beginning. Double check the piping trueness with a sharpie and a wide long bastard file.