Jasonty

Hey folks, I have a question regarding ignition timing. I just threw in my new distributor, and now I'm timing the car. My question is, do I set the base timing with the vacuum advance attached to the distributor or not? I pull the vacuum off, and the idle jumps down, so I'm just wondering if this affects base timing. I have the base timing set without the vacuum advance attached right now, but it still feels a bit off. Thanks in advance folks! Also, what should the idle be set at in Park on an 81?

Rooster

I'd adjust your timing w/out vaccuum advance hooked up - might require you to reposistion your distributor some - stock rpm at idle shouldn't be much more that 700rpm i'd think - -hth

vettfixr

There are three components to setting up your timing. Base, centrifugal, and vacuum advance. You should set your base timing up without the vacuum connected.The best way to set base timing is, while looking at the timing marks, rev the engine until the timing no longer advances. This should come at around 3000 rpm. The timing should be set to 34 to 36 degrees max advance. Once you have that set let the base timing fall where it will. This will give you maximum advance and a good base. Once you've done this connect the vacuum advance to a ported vacuum source. This will give you no advance at idle but will advance once the throttle is opened. Typically this setup will give you 10 to 12 degrees initial and 34 to 36 max advance. If you drive the car after and it pings or chugs back off a little on the base timing. If this doesn't cure it you may have to switch vacuum cannisters to one that only allows about 10 to 12 degrees vacuum advance. See Lar's papers on setting up the distributor for the right part numbers. Good luck.