" O " ringed mopar mega block? Having a serious problem with my SCE copper head gaskets leaking coolant. Tried everything to seal them up with no results.
So I want to try and use a Cometics head gasket. Never used them before. Will a Cometics head gasket work with an O ringed block?

I don't think so. The center gasket is stainless, it probably won't conform to the -ring. I'd give them a call.

Sounds like you need a reciever groove to help seal the motor Regardless of which type of gasket

Tap a stainless wire in to the groove and file it
flush

Just put moroso stop leak in it. Every set of cosmetics I've used has needed it too.

Use UltraCopper silicone around all water and oil holes,let cure 100% and retorque the head bolts.

That sounds reasonable Bob. I would caution to not make it too thick as you might run the risk of it splitting when put under torque load, just a thought.
Should be no reason not to be able to get the water sealed up.

Aren't the SCE's silicone beaded to start with?

We have been using UltraCopper on copper head gaskets for years with zero coolant leaks.O-ring and reciever grooves with copper gaskets is a foolproof way of sealing compression,but unless you get 100% annealing of the o-ring in the gasket and 100% gasket enbeddment into the reciever grooves the flat surfaces tend to not seal.Apply a coating of UltraCopper silicone around all coolant and oil passages on both the block and head side,being carefull not to put it to close to the oil passages so it doesn't migrate into the passages causing restriction.It is important to snug down the head bolts and allow the silicone to cure for at least 24 hours,then final torque the bolts.It works better than any of the coated copper gaskets.Sometimes the copper gaskets are too hard and must be heated to get proper annealing and some gaskets are stamped from a sheet of copper and the thickness varies.Soft evenly rolled gaskets are the best and ones that are lasered or CNC cut are more uniform in thickness.
If your block and,or heads are o-ringed or have reciever grooves and you want to use Cometics then fill the grooves with a filler like Alvins' LabMetal or similar.

Sammy use hylamar to seal your head gaskets, will never leak again 2 even coats sprayed on.

Hylomar is the stuff, just don't get it on your fingers.

R.

Are you using new gaskets? If the O-ring stands out more than .012 you will also have trouble. A .010 deep .041 wide receiver will allow the gasket to pinch tighter. Some o-ring jobs are horrible. The fit of the ends is important. Cosmetics will work with job weld or copper o-rings filed flat. As always if the surfaces are not flat nothing will work

Could you deck the block to erase the grooves, then adjust with custom gasket??