This applies to my BT7 tri-carb.
All of you experts out there provided a lot of helpful information
that helped me resolve the problem with my carbs. I believe the miss
was mostly caused by carburetor synchronization although it was in
several areas.
1. I had the carbs plated in electrolysis nickel. This changed the
tolerances between the piston and dashpot. The S.U workshop manual
has a test and the fall rate needs to be between 5-7 seconds. The
fall rates varied from 5 to 15 seconds depending on the dashpot. I
fixed this by sanding the dashpot and or piston/dashpot interface.
The S.U manual states you need to replace the dashpot and piston,
however, because I had plated the parts I figured I could fix it and
did. There was also some pitting inside one of the dashpots that may
have affected the vacuum when the piston was at a certain position. I
filled in the pit with JB Weld, which is not an easy thing to do.
2. The throttle shaft forks were not actuating the throttle plates
uniformly but adjusting the throttle forks took care of that.
3. The mixture was somewhat lean and it was adjusted.
4. The micro timing was off. I worked with the vernier adjuster on
the distributor to fine tune the timing.
It still misses a little at times, but the problem has been greatly
reduced and it seems to be going away as the various parts bed in.
Many thanks to all of the experts and healey enthusiasts alike!
John Spaur
San Jose
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