What are the tell tale signs of impending HG failure?

[KClarke]

I was told that rough idle and missing is a certain sign. Before I freak I thought that I'd ask here.

[sabbySC]

Keith you've got a 302 you shouldn't be having HG problems, especially with iron heads. This like rough idle and missing are more likely ingnition related. Take that accel coil off and try a regular coil first.

If it were the HG's you should be able to smell the sweet antifreeze smell coming through the exhaust. White smoke should be evident, more so than usual. Also you're oil should havve coolant in it and vice versa.

I wouldn't sweat it if I were you, the problems you're describing can be attributed to many other things. Are you experiencing any surging? Or is it just a miss at idle?

[KClarke]

Sorry for the confusion Sebastian. I'm talking about my 91 LS with n/a 3.8L. The 5L is rough but that's the cam, but otherwise runs fine. The last oil change I did on the 3.8 was free of coolant.