Try the penetrating oil "PB Blaster." It's available at Autozone, Checkers,
Wal-Mart, and the like for around $5 for a large can. It's the very best
penetrating oil available commercially.

Incredible stuff. Since I started using it last year, I haven't met a bolt I
couldn't free. I have done a fair amount of exhaust system work this past year,
too, including disconnecting the exhaust manifold header from my 1991 Civic.

Let soak five minutes, try to turn a bolt. If no go, soak again. Tapping
carefully with a hammer may also vibrate free some of the rust etc. holding the
threads tightly as well as help the PB Blaster reach farther.

Better, let soak with PB Blaster over a day or so, with some driving in between.
Repeat for a few days.

I have been spraying the PB Blaster into an old tuna can and then using an eye
dropper or syringe to better direct the PB Blaster on hard to reach bolts.

Also, one of the 14 mm hex head bolts at my exhaust manifold had so corroded
that a 14 mm socket would not work. I tapped a 13 mm socket into place and
voila, it came off.

I replaced all bolts.

I trust you are using breaker bars or pipe extensions fit over your wrenches to
give you extra leverage, yes?

That's vital. The aforementioned bolt still didn't come off without a 3-foot
pipe extension on the breaker bar/ratchet wrench.

"Ropert's Aloha" <removeropertg001@hawaii.rr.com> wrote
> I'm trying to get a manifold off a Honda Civic in order to replace the
> clutch. The book calls for removing the exhaust manifold. Off course the
> bolts/nuts are frozen. I have soaked them for a couple days in penetrating
> oil and still no go. Is it possible to heat them up with a torch and have
> them come off easily??? Or will they still probably break off??