360 Tune Up

Rock Able said
Thanks for the challenge, guys. I had already checked this distributor and since it was new, I ASSumed it was ok. After mapping the centrifugal advance curve, I plugged in the vacuum line to find that the diaphragm was open. No vacuum advance. So, I'm starting over literally. Fortunately, I had another distributor and mapped it. I also returned the Edelbrock 1406 to base #1 tune.

The 2nd distributor has the following map.

  1. Idle (750 rpm) 7 degrees
  2. 1000 rpm - 12 degrees
  3. 1500 rpm - 24 degrees
  4. 2000 rpm - 26 degrees
  5. 2500 rpm - 28 degrees
  6. 3000 rpm - 31 degrees
  7. 3300 rpm - 34 degrees
The vacuum canister on this one has 15 degrees of advance. I get 17-18" of vacuum at 750 rpm and 22" at 2000 rpm. Vac advance is hooked to manifold vacuum.

The lack of vacuum advance would explain the higher temps cruising under load at 2400 rpm or so. Correct? It is supposed to get hot this weekend. So, I plan to do some more temperature testing. I have a new electric fan coming today and hope to get it installed tomorrow. Mileage tuning may have to come later.

What is the recommended amount of total centrifugal advance and the recommended total of vacuum advance? Is 34 BTDC about right?

Thanks for your help!
Click to expand...

Looks OK for the centrifugal advance, I think it would be better to limit it by about 5 degrees so you can have more initial timing. Also the vacuum advance should be hooked up to ported vacuum, not manifold. I recently helped a friend with a stock 360 in a '79 pickup that was running funny; didn't idle well and had some hesitation when accelerating along with bad gas mileage. Turned out the vacuum advance was hooked up to manifold vacuum; once I switched it to ported and reset the base idle advance the idle smoothed out and it was much more responsive and nicer to drive. Some engines can use manifold vacuum advance but from my experience stock or near-stock Mopar engines really don't like it.