Kip's41,
If you are determined to repair the heat riser properly, it will probably require you to remove the intake/exhaust combo to separate the two and gain access to the heat riser innards.
The bolts that secure the two manifolds to each other will sometimes break when wrenched on. This means new bolts, easy outs and much creativity. Although it doesn't always happen this way, that area is usually a 'frozen zone'.
If all this were to happen, with just a bit more energy, you could have the manifold combo surfaced at a auto machine shop and the whole enchilada would be good for another 40 years.
If you can fix the heat riser to your satisfaction from the outside, this all becomes a moot point. These are just some points to think about.
Stuart
