<VV> Single Carburetor-reply

[djtcz at comcast.net]

John Ingram wrote 

The problem is when I watch the vacuum advance when I blip the engine 
from idle it dips before it goes up, after that the advance is 
normal. I have set the timing by making sure it does not go above 32 
degrees BTDC at high rpm. I need to get rid of the "dip". The 
engine sometimes stumbles when it dips and may even pop back through 
the carburetor. The vacuum is connected to the vacuum tube already on 
the carb, not from the manifold. Would manifold vacuum work better? 
JI 

======================================= 

Hi John, 

Is that 32 degrees total at high rpm with the vac advance still attached? 
I believe that "total timing" of between 34 and 38 degrees would be correct only if checked (measured) while the vac advance is disconnected. 



Referring to this chart - 
http://www.autosportlabs.org/files/distributor_specs_163.jpg 
(1) At high rpm with closed throttle and vac advance hooked up the "total timing" for a 110 could be as high as 58 degrees 
14 (initial) + 20 (max centrif) +24 (max vac) = 58 


(2) The "high rpm" needed to coax full centrifugal advance would be 4200 to 4800 rpm depending on model