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Frozen exhaust manifold bolts

I have a 1973 Buick convertible with a 455 CI engine, virtually all original with 66K miles. Recently, I developed a leak in one of the exhaust manifold gaskets. They have never been changed and one/two bolts are frozen. Don’t want to risk breaking them and necessitating engine removal or having to drill them out. A mechanic has tried heating them, among other techniques, with no success. Are there any other ‘magic’ techniques that may be used? I’d appreciate any advise. Thanks, Lance

Overnight soaking with PB B’laster might do the trick. It may take several overnight soakings, in fact.

is this a threaded bolt, which has a nut on it? or is it an actual bolt< which must be removed from the block?

I don’t imagine you drive it much. Just live with the ticking noise. From such a small leak, you won’t have to worry much about exhaust fumes. And, in regards to the possible broken bolts…You won’t have to remove the WHOLE engine…just the head. This requires removing the intake manifold (possibly the distributor, too). Not brain surgery, but mid-level engine work. There are no easy fixes. Soaking it in oil is unlikely to do any good. Those bolt holes are pointed up. Capilary action will only take you so far.

A mechanic i worked with would heat the bolt and then melt a wax candle onto it. somehow it is supposed to pull the wax into the threads.

sounds crazy but it worked every time for him.

PB blaster works well also. Apply it and then tap on the head of the bolt.

Don’t try and manhandle it out though. if it feels like it doesn’t want to come loose don’t force it.

Get them warm by running the engine for a short period and then spray them with B’Laster PB. Spray both the bolt heads and the manifold to head interface. Do this a couple of times before attempting to remove them. Give the penetrant time to work. Like a half hour or so. Then try and remove them. Unfortunately, these bolts waste about the shoulder and are often too far gone to be removed without twisting off. Most of the time, some part of the bolt protrudes out of the hole and you can tack weld a nut to the end of the bolt (weld through the center of the nut) and remove them that way. But it’s a cr@pshoot and you have to decide if it’s worth it to fix the problem. For me, that car would definitely be worth the effort to fix correctly.