Have you checked the function and range of your vacuum advance lately?
Not easy these days to find the correct vacuum advance for the right engine and year. 235 1962 in this case.
The local parts suppliers don't even carry it, including NAPA.
And every one of the online and catalogue places sells the very same vacuum advance for all 40s-60s 235s, although they had different specs originally.
I got one of those but it only starts advancing the distributor after 9 inches of vacuum pressure.
1960 truck shop manual says should start at 4 inches for my correct distributor.
I have also a PCV system which drops the vacuum considerably, so the vacuum advance hardly engages. Centrifugal advance works OK.
There is only one place online I could find with the correct one - they are backordered for about 3 weeks.
Does anybody know where to find a GM# 1116089 vacuum advance. Listed as 55-57 pass. and 58-59 trucks.
Btw: How much vacuum pressure drop is normal when connecting a PCV system to the manifold compared to no PCV?
I am mostly looking for all the benefits at light load/cruising from a vacuum advanced timing, like better response and mpg.
Another benefit might be the blapper at deceleration in the exhaust pipes should be less or gone, I believe.
