I run premium gas in my 250. The difference in performance and mileage makes it worthwhile! I'd use the 110 octane leaded gas except #1, it's for off road only, so I'd have to put it in a can ( they won't let you put it directly in the tank ) and #2, it's $9.00 a gallon!!! This is for gas that was 25ยข when my car was new! Anyway, do a compression test and see what you have. The only thing I can think of that would have changed by removing the head is the carb. Did you turn it upside down when you took the head off? If so the sediment in the bowl may have clogged a jet. If you have an air compressor take out the idle mixture screw and blow air into the hole you removed it from. Be aware that fuel will spray out of the carb throat. put the screw back in ( only hand tight ) and back it out 2 turns and see if this helps your running. Check all your vacuum hoses for proper connection and adjust your idle mixture for best running when the engine is fully warmed up.
btw, the manual is a 71-85 Chilton manual. Yes its a Felpro gasket. It's not leaking now, but I guess you are saying it may still be off enough to block coolant flow, hence the light smoke and hot exhaust fumes. I didn't move the distributor and the carb was left in the upright position when removed. Vacuum lines are all on as well and power brake booster hose is connected.
I'm sorry but I have to say this. If Felpro can put the effort out to make a replacement gasket, while can't they make one that actually freakin' works?!?. That's just stupid to me. I mean, all of the work it takes to replace a blown gasket, only for the work to be completed with a badly designed head gasket. No love for the straight sixers...
Not the engines fault ( I love mine ), it's just a shame you can't buy decent parts anymore! I haven't had to do a head gasket yet, but I'll sure remember to get something other than Felpro, if I ever have to!
So i promised a follow-up, and here it is....I'm an idiot. Just sayin.... I had to replace the line running from the front of the valve cover to the intake manifold, it was dry rotted badly, it runs really well now. Just gotta replace cap, rotor, wires and points and it'll run even sweeter.
