17 month update! The Z hasn't seen much action as I've been dealing with a perpetual throttle-hang problem and inconsistent low-speed fueling--lots of popping out the carbs at low load/throttle openings.
The low-speed fueling was dealt with by a trip to Keith Franck's house on New Years Eve 2021 to use his custom progression-hole drill fixture. The first p-hole in my 45DCOE 152's was too far upstream, you couldn't even see the throttle plate through it at idle. This is a common problem with the 152's and Keith's fixture was the perfect tool to fix it. It turned out to be the correct diagnosis! I was rewarded with virtually no more popping out the carbs during low-load operation, the freeway cruise home was the smoothest it's ever been... besides the fresh rock chip in the windshield.
But now the rev-hang problem was even worse, although the engine would return to idle after a sharp throttle blip which hadn't been the case before. This is an issue I've been dealing with, at various severity levels, for the entirety of the 9+ years I've owned this Z. I was invited to a cars and coffee event this past Sunday, 5/29/22, which was inspiration for the next round of trying to fix it. So the carbs came off for the 132nd time, this time with the intent of resetting the throttle butterflies. I decided to pull the carbs off the manifold while on the car as to not waste the manifold gasket which had been port-matched when I had it apart last year.
What I also discovered were some slight interferences with the TWM manifold (would love to replace this janky manifold with a Datsun comp or Harada piece) as well as a non-functional accelerator pump on the #2 carb. I ground down the manifold in the offending areas with a file and radiused Dremel burr, this worked very well. Swapping accel pump pistons from carb #2 and #3 did the trick for making the #2 pump function again! I chalked it up to slight tolerancing issues. I then spent a good amount of time with a flashlight backlighting the butterflies, trying to get them as sealed as possible. I first set all the bearing preloads with the throttle shaft nuts as to set the throttle shaft in place. Then I loosened the butterfly screws enough to get the butterflies moving. Setting the butterflies was a matter of seeing where the light was coming through and trying to set it in a position where the light "leak" was even and minimize. The butterflies are eccentric in shape so turning them a bit here and there helped find the optimal position, along with snapping the throttle shaft for a bit of self-alignment.
And I finally have the crisp throttle response I've always wanted! It could be better but it's a massive improvement over what it was. I'm still missing that "zzzzz" noise on overrun when snapping the throttles closed but at this point, I'm happy. I made it to the C&C yesterday and did about 160 miles of excellent ripping through the East Bay and Santa Cruz Mountains!
Photos from recent drives:
My son likes to service his car while I work on mine, we ensure that safety best practices are always followed.