Ok having limited the internal distributor advance on my stock Y block, there's a lot more room to play with in terms of initial timing and the vacuum advance at the far end, compared to OEM. The mechanical distributor advance is now limited to about 20° on the crank w/light springs so it comes in early. Running 17° initial. But had to back off on the vacuum advance to almost nothing to keep it from rattling at steady cruise. It's kind of subtle but it's there. So today pulled the cap and inspected the innards, a drop of oil on the felt, cleaned the crud off the rotor tip, made sure the advance plate was moving freely etc. Applying vacuum to the can, it hardly moved. In fact I thought the diaphragm might be bad so I removed it to check. Had been adjusted with the allen wrench almost fully out. Isn't it better to (for a street motor) to run as much vac*** advance as she'll stand? Let's try that. So then I ran up the vacuum advance all the way clockwise minus two turns and the breaker plate comes in fast, far and wide with just a little vacuum. Then I backed off the initial timing to 12°. Observed about 32° total mechanical advance on the damper when spooled up and then maybe 45° w/vac advance connected. Seems to run good on the highway and no rattle that I can detect. Maybe I could bump up the initial a tad just short of any ping or detonation or, maybe run slightly more vacuum advance or, even connect vac advance to manifold. Seems to me it may have been shortchanging the low load advance at steady highway cruise speeds, because the RPM wasn't bringing all of the mechanical advance in. But it sure sounded a little ragged at times. Is this a better strategy, lots of vacuum advance, to take up the slack?
The Jalopy Journal
