well, i have been having some issues with my 305 tbi. the other day while driving it home i noticed that it started to over heat. i cut it off and coasted for a lil but, then turned it back on. no changed, stopped and there was no water in over flow or radiator. filled her up, drove a few days and the same thing happened again, but once it got to the 240 mark the therm opened and it cooled back to normal operating range, 160 mark. checked radiation again and low again. all the water that was going into the over flow was also not going back into the radiator. so the over flow, over flowed(lol). checked the oil last night and it showed that the oil was way over the 'max' line, but checked it again today and its below the 'low' line. pulled the plugs(please dont bitch, i know i should not have gone with the quads, but i was young and stupid) http://http://www.facebook.com/photo.php?fbid=460793263948499&set=o.207880215268&type=1&theater.
all it really shows is that 5 and 7 are a lil more chared on the connecting link to the S.P. wires than the rest of them, but seem to be 'ok'. no informal ware or anything. im completly lost here, either way it seems like i will have to break open the engine.

 

if you are losing coolant you need to figure out where it's going, is there an external leak or is it internal ie headgasket or intake gasket. Are you burning coolant or are you building pressure in your coolant system. Is there air in your coolant system which could also cause over heating.

 

well, after checking my oil again, its not 'chocolate milk' like, just looks like normal oil, tho i am low on oil. im not burning anymore white smoke than usual, i believe i have a worn valve seal, but its not bad. i believe there might be some air in the system due to i let it run dry some how. it was fine all winter, checked it spring added a little water. and now it was like bone dry. ive been letting it run with the cap off. it does build pressure. but dosent like taking back the water/coolant that is in the over flow. i have noticed that at one time both the upper and lower radiator hoses had negative pressure, both being sucked in when it was cold. i dont know why.

 

Its possibe you just have air in the system. If you really did run it bone dry (or close to) its very likely you have quite a bit of air in the system and it needs to be burped. In case you dont know how to burp it, fill the rad abt 3/4 way and run it. Watch the level and i always rev it some too, idk if it actually helps or not but i do it and have never had any problems afterwards. as it warms up, add some to almost the top. When its close to the very top, put the radiator cap on, making sure the overflow is filled to the middle of the "low" and full" marks- this way as you let the system run it will take some from the o.f. or return it as needed until the rad is full, but you wont get the o.f. too low or too full. If you dont have a coolant loss, this will work. If you try it and still have the issue, you have a coolant loss.

The problem is, however, why did you overheat in the first place?

I think you should do a compression check/leak down test tho, definetly before you tear that engine apart!