Bicycle Mechanics - Stem issue

I have an old Cinelli stem with Cinelli bars. It has been sitting for evidently quite a while. I tried to remove the stem head bolt with the appropriate allen wrench, but it is so stuck,and the metal is so soft, I stripped the hex pattern somewhat. I dripped in some PB blaster and thumped it several times and let it sit. Still no move...

Is there another method to remove the stem and bars?

Thanks

since you stripped the bolt then take a hacksaw and cut the bolt at the stem opening. find a replacement bolt.

They use a cone wedge, you may have the threads seized inside with rust ..

these stuck in the fork?

drill the head off, use a punch to drive the wedge down.

Yes, i suspect hidden rust inside. I will try your method, or drill the sucker out and hope to find a suitable replacement. It's on a 70s Gios Professional that I want to restore. Thanks

Try flipping the bike over and shoot you PB down the inside of the fork, hit it several times and probably set overnight. Then get a new 6mm socket style allen so you can get some leverage. Since it it rounded out make sure the allen is lined up properly and the hit it with a mallet to get the wrench in as far as possible and turn slowly. Then brace the front wheel with your legs and turn the stem if you have an old wheel that would be better just in case you might bend it while turning stem. On a very rare occasion I have had to cut the stem off to be able to free up the wedge bolt, take your time and it will probably come out.

Might be able to hammer in a Torx wrench and make some headway on gripping inside the rounded allen socket.

Before drilling out the head on that stem, give a bolt extractor bit a try to avoid "collateral damage" to the Cinelli stem. They are not cheap to replace these days and popular sizes go for even bigger money, so it's worth taking you time and extra care to remove that bolt with patience.
Screw/bolt extraction bits are available in most hardware stores.

Chombi