the other day i was running my blazer down the freeway and it started to get a little hot, when i pulled off it was idlling funny and making a different idle sound. i have since lost significant power and im smoking a little. i checked under the hood and on the passenger side by the #7 plug it is seeping smoke out of the exhaust manifold? what could this be?

 

sounds like it. what's the oil and coolant look like? brown coolant, or milky, cloudy oil is good indication.

 

ya the coolant is brown, i just changed the oil pan gasket and havent really ran it. got in it when i was done fired her up,tried to open her up a little but didnt have any real power. so i parked it. opened up the valve cover passenger side and found a broken rocker arm.. how could that have happen? when i replace it, should i replace all of the rocker arms? rods too? how hard is this task, and what about the adjustment of the valves?

 

i drained a little of my oil, no coolant that i could see. but the oil is already BLACK and i only ran the engine for about 20 minutes, can i flush the oil system with something to get all of the impurities out of it? my dad has a 69' blazer thats a street rod with a 350 in it also, he is using a full synthetic oil thats 20/50. isnt that too thick? he told me to use the same and i did, i hope this doesnt screw things up with my motor. will it??

 

wow lots of questions, but i have some answers, replace just the 1 rocker (the others still work) the smoke coming out of #7 cyl could be cuz the broken rocker arm punched the valve cover, as for the oil, put an oil cleaner (or type f trans fluid) and run the truck at idle for 10 min then change the oil, u just have a lot of gunk in the engine (could have contributed to the broken rocker) it could have gotten hot from a stuck thermostat, and the best way to check for a blown head gasket besides the color of the fluid is a compression test (i had a blown head gasket and when i pulled the plug a bunch of antifreeze pissed out )
best of luck, if you ar going to learn to wrench on cars, a chevy is the best start