Originally Posted By: JimW
But, I'm concerned. Is it possible that inorder for me to be at 35 degrees total timing (base + mechanical) that I have to have the base timing set to 12 to 14 degrees advanced?


Is this an old Delco-Remy six cyl distro with really low value mechanical advance? I've got one on my Brand R engine. From the factory it would do 11 degrees mechanical advance total! No aftermarket available.

I hacked my distributor to get about 20 from it. Here's the description: http://wps.com/AMC/195.6OHV/Distributor/index.html



Your light-load-cruise vacuum sounds too low. Could be too low cruise rpm, even under-square motors from the 50's on should be over 2000 rpm at your target cruise. The motor may be OK with all that pumping but the low vacuum means you're probably driving the carb on enrichment circuits (eg. power valve) and that's bad for mileage. If you bring cruise RPM up you might find cruise vacuum goes up.

With light load/high vacuum, and correspondingly lean-ish mixture, then the vacuum advance unit will help the thin mixture. All this junk interacts, and it can be a bear to wrestle it into cooperation.

It might simply be that your 33" tires dropped cruise RPM and caused all your "tuneup" problems...