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<p>Yeah, that looks pretty solid to me. Check if you have vacuum advance at idle where you're checking the timing. Better yet, just pull the vacuum line off the dizzy and check it - you might be running on the hairy edge of the vacuum advance port slot versus the throttle plate position.</p><p> </p>
Thanks for the input guys. I am running the Edelbrock 1406 carb and connected to this port:
I think the vacuum advance works because when i disconnect it at idle and cap off the line the idle drops. When I reconnect at idle the idle increases.
Could this have anything to do with incorrect valve adjustment? I am running adjustable rockers with hydraulic lifters on this 390. Maybe I should go back and check rocker tip clearances?
<p>Fords shouldn't have vacuum on the vacuum advance at idle.</p><p>If this is "ported" vacuum which is what Fords need, and the carb is supplying vacuum at idle, the throttle plates are open too far and they are allowing the ported vacuum slot to get vacuum.</p><p>This can mean a few things - the cam is too big so you need to open the throttle plates too far to achieve a high enough idle speed, or the timing advance is too retarded, requiring the throttle plates to be open too far.</p><p>Disconnect the vacuum advance, plug the line, and time the engine for the base timing at the correct RPM. Once that is done, recheck the vacuum advance port, you might no longer have vacuum there if you had to lower the idle at the carb.</p><p> </p>
<p>On further review of your picture, your vacuum advance should be connected to the "timed vacuum" not the "manifold vacuum". Still, disconnect the vacuum line to the distributor, and set the base timing and see what you get at the "timed vacuum" port.</p>
In the picture you posted, notice that the timed vaccum port is higher than the manifold vacuum port. This means that the timed port is above the throttle plates and has no vacuum at idle. The manifold vacuum port is below the throttle plates and will have constant vacuum. As Krewat says, use the timed port for proper vacuum advance. Good luck.
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