Originally Posted by PotteryPal
I was checking the tuning on my 67 289 with a vacuum gauge and noted aside of it being on the low side of the normal range (i.e. 18-20in mg) that under acceleration the vacuum increases sharply. In my experience this isnt normal. Shouldn't it be decreasing under acceleration?
I also have the problem that I can only turn the dizzy so far clockwise before the vacuum advance nipple hits the coolant hose. Any ideas the fix this issue as well?
Check your ignition timing with a good (strobe) timing light -- with vacuum hose to the distributor disconnected and plugged.
The conditions you describe (low vacuum; vacuum pot interference) indicate a distributor that is a tooth off.
If you are still running a "points" distributor, ditch it for an electronic type -- in the long run, they'll give more power, increase fuel mileage, and hold a tune better and longer.
At your altitude (Houston), your stock cam should give a steady 19-20 inches at 800 rpms.
Bosch Double-Iridium plugs gapped at .040 for a long-life tuneup.
Good Luck !!