94z28 overheating and now is missing

I have a 94 z28 convt. stock 5.7 have had it for about 30 days, this week I decided to switch over to castro syntec oil w/K&N gold filter
after restarting the car I noticed radiator fluid coming out of the overflow. The fluid was nasty, sand was all over the engine, lint, rocks and all kinds of crap was stuck to the radiator. I flushed the system
w/a engine flush put a new 180deg. thermostat, got the temp to drop
constant at about 210deg. at idle. Now it's missing and knocking like it's
not getting proper fire but it not missing at idle.....I'm ready to go back to my mustangs...

Ok, you need to check your engine oil level first off. It's possible that you've some how drained all your oil, and that'll explain all of it. Check your cap and rotor, plugs, wires, check for leaks every where it could possibly come out. And take your car somewhere to get if flushed, that stuff you get at the store is crap, and you have to do it three times for it to get all the shit out. but that's what I'd do.

I flushed the system several times until water ran clear and put in new GM radiator fluid also checked
the oil and clear of water, no fluid at the exhaust
pipes. The car ran fine until I flushed the system
checked the coil and plugs and all seems good

So at idle it's fine, and when you give it some gas it starts knocking and missing? Well if this is the case then it might just be a coincident( pardon my spelling) that another problem showed it self at this time. If your bearings are going bad then you might not notice it at idle, but when you give it gas it sounds like a knock and could feel like improper timing. Or your timing could be off, wich would be the missing problem, and you have a rod knock. I would check the timing, and take the valve covers off and check for play in the push rods. Run you car for codes, and don't get a mustang. that's all I can think of right now.

codes :)

I beat you..said it already. LOLRun you car for codes, and don't get a mustang. that's all I can think of right now

Hmm what is your oil pressure at? because if you have low oil pressure and you have knocking and clanking it could be that your engine bearing is going.

blast you 92RS, i didnt even see that. ah well, guess you got the forum covered, im gonna go sleep :)