I set my timing last week.

I thought I had done it right (well, acording to Haynes...) 0 Leading and 20 Trailing

Last night I was looking and it appears that my Dist has had the vacuum hose removed. hmmm

The car was running well, a bit lumpy on idle. Drove it 400 miles on the highway seemed okay.

So if the vacuum line is off, then I am at full advance and should set the timing to Advance settings (10-20 or 16-24)?

Please help, going racing this weekend.....
Thanks

 

Well I am pretty familiar with dist. the vacuum advance if disconnected will not work it needs the vaccum so you have nothing there just your intial timing setting as for the mechanical advance thats comes in with rpms to the preset advance. bottom line I would leave the vacuum off and run some more intial advance at least for racing. Thats only if your drag racing where you come off the line at high rpm anyways. other type racing probably put the vacuum back on and watch your total advance don't want too much.

 

Leave the vacuum advance disconnected, rev engine to 4000rpm and set total ignition timing. I'm running 20*L and 10*T. Any more than that I believe is asking for trouble.

 

Crankit, that would work if the vacuum advance was on at all rpm, but it isnt. Around 2500-3000rpm the leading vacuum advance is bypassed and aroung 4-5000rpm the trailing vaccum advance is also stopped. The vacuum advance is basically there to fill the gap before the centrifugal advance kicks in. Increasing your timing to compensate for 0 vacuum advance will create detonation problems at high rpm because of the extra advance.

The vacuun advance also helps emissions by coming on when decelerating no matter the rpm... this helps burn off excess fuel.

I'd do what most everyone with aftermarket carbs do... disconect it and forget. I personally find the engine runs MUCH smoother without vacuum advance advancing the timing when it isnt needed. Of course, fuel milage and emissions will be affected.

 

Since we're on the subject, I bought a underdrive pulley with the marks on the pulley for 12degrees and 23 degrees, then when I went to set the timing at 4K it was showing it way past that! I had it set stock when I check it so I know the marks were off some.