Any one knows how to get muffler screw out connected to enginge months ago with a kittle lock tite and unscrew one but the inside of head of other rounded out inside since then tried vice grip but have been unable to loosen screw any help out there?

Go to Sears or a car parts store and get a bolt extractor. Another possibility is to use a dremel with a cutting disk to carefully cut a slot in the screw head and then use a flat screw driver. When you replace the screws, consider socket heads instead, they are less likely to strip.

Don't no if others would agree and I am not sure what size the screw is but you need to drill out the screw with a drill smaller than the minor dia of the screw. You then may need to chase the threads with a tap after drilling to fix any threads that may get damaged.
This can be hard to do without a drill press or mill however. If you don't have the equipment I would check with a small machine shop and see if they could help you out.

I use to do this kind of stuff for free in my shop when the occasional John Q. Public wandered in. It only takes a couple of minutes if you have the right equipment.
However the shop is now no more.

Forgot to add, be carefull chasing the thread, it's much harder to get a broken tap out than a screw.

If it was red locktite, then drilling it out will probably be your only option.

If it was blue locktite then follow piper_chucks advice and grind a slot in the head of the bolt, then use a soldering iron and heat the bolt down at the threaded end, this will take a little time but get it as hot as you can, this will release the locktite so you can turn it out. I use the heat trick to get out servo screws on metal gear servos to replace the servo arms, works like a champ.

The other thing, since this is on an engine, if you have one of those little butane torches Hobbico makes you can use that to heat up the bolt, just be careful and apply the heat slowly and evenly. Even a propane torch on low heat would work.

If you have a good heat gun, that has a small tip, it will also soften the loctite. Lockwasher should have been sufficient and not used Loctite IMHO. If you use a tap, remember it may be metric threads. Use hardware prescribed by engine/muffler mfg whenever you can. If entire head of screw is exposed, and all else fails, you can probably cut the bolt head off with the Dremel. Be careful not to damage engine/muffler when doing this and keep ALL metal debris out of the carb and exhaust (muffler in the way I know). Keep plug installed.

Good luck

Bruce