Status report
Left work early and did a bit of tinkering. Now I am more puzzled than before.
1. Installed the nice new shielded MSD magnetic pick up wire. No discernable difference.
2. Per Rob's suggestion, swapped out the 60 idle jets and replaced with 55. It made a difference. We were actually able to get all 8 cylinders firing, albeit #8 was tempermental and had to get the mixture screw in just the right spot. It would idle around 900 rpm without popping or backfiring. It would blip OK, but hold it at 1500 or 2000 rpm and the popping and backfiring was relentless.
Cylinders #1 and #5 ran noticeably hotter than the others
Turn it off, start it up, and it would pop and backfire again at idle.
Did not have time to slap on the timing light to check the quality of the spark.
3. Original carb settings as dynoed by Tand L are:
Weber 44 IDF
Idle: 60
Main 135
Air 175
Venturi choke tube 32
Aux Venturi 45
4. The weights in the distributor move freely
5. Removing the rev limiter made no difference
6. The MSD is solidly grounded to the chassis. Checked with an ohm meter as well.
7. Ran carb cleaner through the idle circuit.
Conclusion:
A. It still ain't right
B. Changing the idle jet helped, but it still seems way too sensitive and unstable.
We changed the Air jet to 180 and it was the same or worse, so put it back to the 175. Have not changed the main jet (145 is the largest we have in our box of jets)
C. I still wonder if it could be the MSD box. Ryan wants to put an MSD on his 1982 911, so this may be an excuse to bite the bullet and get another. Ugh.
D. Question: Should we fiddle with jets? If 55 is better than 60, maybe we should try a 50 idle jet?
E. As Ryan so astutely observed: "what ever changes we make it runs different, but still runs like crap"
The Curve Ball
Here is another issue not mentioned before. Early on I replaced the paper intake / carb gasket with a spacer, about quarter inch, made from a plastic material to stop the carb boiling after shut down. They were not specifically made for IDFs (I think they were for IDAs), but was told they would work. The outside shape matches but the inside is not concentric with the carb bottom and intake manifold opening. The spacer has a slightely larger diameter opening. Could it just be that it is screwing up the flow?
But my memory is that the carbs were behaving the same before we put in the spacers, so never considered that a cause.
Bottom line:
A. More jet fiddling, or
B. Swap out the MSD
C. Go back to the fiber manifold / carb gaskets
(By the way Rob, what is the advantage of the Crane Hi-6 versus MSD?)
Opinions?