Thread: 544 B20B help
View Single Post
Old Jul 22nd, 2021, 16:22   #20
142 Guy
Master Member
 
142 Guy's Avatar
 

Last Online: Yesterday 18:18
Join Date: Jul 2020
Location: Saskatchewan, Canada
Default

The distributor appears to be from a late B20 from the last of the 140s or the earliest 240 before they received the OHC engine. It doesn't even show up on that list posted by Derek. I thought all the B20s in the final 140s and the 240s in the US were K jet starting in 1974 or 1975. However, carb equipped 140s and 240s did continue on in Canada well into the '70s so perhaps it came from a Canadian spec B20.

I think the designation means that the distributor is equipped with vacuum advance whereas the typical B20B engines would be equipped with vacuum retard. The typical distributor on a B20B pre 1974 would be a JFUR4. I don't have any data on the later distributors. It might be equipped with very little centrifugal advance which may be the cause of your lack of advance or the advance mechanism could be stuck. Pull the points plate off and see if the centrifugal advance operates smoothly. If it does, then you may have to dig up the specs for a late B20A or B (perhaps Canadian spec) to find out what the specified advance is. The advance curve may be wrong for your particular B20B depending on whether you have a high or low compression B20B. If so, you may have to investigate replacing the advance mechanism.

As an observation, if the distributor has not been rebuilt then it probably has shaft wear which causes timing problems at higher RPM. The distributor on my 1971 B20E worked fine at low RPM; but, as you increased the RPM you could see the timing marks bouncing around quite a bit starting around 2500 - 3000 RPM. A new 123 distributor might be one way to address your distributor uncertainty and eliminate any wear issues.

The top of the piston looks moderately clean. The bigger problem would be the actual combustion chamber. In particular are there deposits on the exhaust valve which runs hot and provides more opportunity for hot ignition sources? Since the engine appears to be out of the car I would assume that you are going to do an engine clean which may address most of the run-on problems.

Last edited by 142 Guy; Jul 22nd, 2021 at 16:32.
142 Guy is offline   Reply With Quote