Posted 2018-02-05 5:07 PM (#557561) Subject: Overheating within 10-20 miles even with good radiator,thermostat, timing not too high,etc.
Hi. this is one for the books,if somebody hasn't resolved their overheating dilema! I have a 1959 Belvedere with a 318 poly that was boiled and rebuilt 15k ago. that was back in 2002 and also had the radiator redone about same time. It has always been a super reliable running and cooling engine for all these years up until a couple years back. What I thought was for sure a thermostat stuck,and it overheated 10 miles out,was just the beginning of my adventures. It fired right up the next day right away after stalling and never getting it restarted the previous night. That was the first wrong guess. The radiator had started to get pin hole leaking just under the tank seam. That really sent me in the wrong direction,because in the long run, the radiator had nothing to do with the overheating either! Turns out the radiator was being taxed by the real issue. I thought I had everything good enough to run it to a local cruise in 8 miles out until I saw the temp. rising and rising until it just died at the last stop sign. I didnt bury the temp gauge either. If my friend had'nt been there with his very high powers of observation I still would be DIGUSTED to this day,f he hadnt noticed that my carb was VERY HOT to the touch! Ok,that has to mean something. Ok folks,here is what I would like to pass on to some other unfortunate soul in Mopar land. Most of you in this era,with the Adjustable rockers exhaust and intakes beware!! I had a hunch and caught it the 1st time using a Compression Gauge. Make sure and check every cylinder with those Exhaust Valves in their closed position.I marked off the balancer to do this ,and with a ratchet and socket turn the balancer by hand to each cylinder's closed [exhaust] position. NOW IF YOU FIND A CYL. WITH LOW OR NO COMPRESSION, you have found the culprit! Much to my disbelief,and gradually over time,so you'll barely notice your car running ever so slightly not as powerful-MY NUMBER 5 exhaust valve ADJUSTMENT had slowly TIGHTENED ITSELF DOWN to the point the valve wasnt making any contact with the valve seat anymore! I adjusted it back down, and all my problems went away! AND IT RUNS SUPER SMOOTH ONCE AGAIN,RUNS STRONG! Goodluck !!
Posted 2018-07-07 11:14 AM (#566211 - in reply to #557561) Subject: Re: Overheating within 10-20 miles even with good radiator,thermostat, timing not too high,etc.
That's very odd, I have driven mopar engines with a burned exhaust valve and it didn't overheat. Didn't run very well though. Had a 361 that would overheat at high speed without the thermostat in. In just about every case (as mentioned) a valve clearance will increase due to wear.
Posted 2018-10-12 12:10 PM (#571567 - in reply to #557561) Subject: RE: Overheating within 10-20 miles even with good radiator,thermostat, timing not too high,etc.
Hate to say it but I agree. Hardened exhaust valve seats would have prevented that problem. Nut's do not tighten them selves rather they tend to work loose. Might have been over tightened right from the get go also.