Vacuum advance? Centrifugal advance? NONE?

[FrankRizzo]

Hey guys. What's the normal method of timing advance on our engines? Talking to a bud who knows lots about 13Bs, and he was convinced that I have a vacuum advance issue. Went down, checked the car, and the "brass warts" on the distributor are present, but have no hoses attached. (I have 2 of them on this distributor).

So, SHOULD I have? Is vacuum advance normally used? Is it centrifugal? Electronic? None?

[Karl Markey]

Hi Frank,
The vacuum advance is not utilized. I believe that the centrifugal runs at full advance all of the time; if you take off the distributor cap, you will find that the (goofy looking) rotor can be rotated within limits of advance without any spring back.
If you want to check timing, there is a small wire protruding from the front housing just above the crank pulley and there are timing marks on the crank pulley. If you put a timing light on it, you should see the timing marks light up (they always seem to be hiding from sight with the engine off). I cannot remember which of the marks should align with the wire. If memory serves me correct 19 BTDC is the typical timing but you won't see any numbers, just 4 marks on the pulley.
Another oddity about the ignition set-up is that both leading and trailing spark plugs fire at the same time. In the street motor, the trailing spark plug timing is, well, trailing.

If somebody spots misinformation here , please speak up.

Regards

[FrankRizzo]

If memory serves me correct 19 BTDC is the typical timing but you won't see any numbers, just 4 marks on the pulley.

Well, believe it or not, when I took a peek just now, the marks were visible with the engine off.



Should I assume the BLUE mark is the correct one? (Pardon the finger intrusion)

[dmccallum]

Frank,
The marks, starting at the top, looking at the picture, are -10,0,10,20. The blue mark is about right for a general setting. For weekend racing, you want to set it at around 10 to 15 DEG. If you wanted to get maximum power you would need to set it on a dyno and it would probably end up closer to 20Deg. Max power is harder on the engine so for regular weekends set it at around 10 to 15 Deg. (blue mark). No vacuum advance.
Dale McCallum