NorthNH and B20Paul are the ones in this thread suggesting making sure u have good ignition and I am with them. Too many times I have suspected exotic problems when it was just a bad cap or rotor etc....use your timing gun on all plug lines as welll as the main line from coil to look for regular spark...if you are getting intermittent spark find out why....Petronix uses the original cap and rotor and in my experience many "new" C and Rs are garbage entire runs can fail so you need to pick up replacements from different store/manufacturer. Guess it could be valves but sort the ignition first...
re overheating while sitting in traffic.....120s do that ....the WP does not push enough water idle and on a hot days the temp will climb while in traffic. give it a little gas so it runs 200 or more rpm faster should cool it down. BTW if the "choke" mech. is set up right, pulling it out a bit will give you 200+ rpm without making the mix richer.
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Patrick, '68 220 , '53 GMC 4104, '97 VW Transporter.