351M timing Issues

[Beach66Bum]

These engines are timed with the Vacuum Hose to the vacuum advance Attached..not removed.

Now that's the first place anywhere that I've read that says timing on these engines (or any engine, for that matter) is with the vacuum advance connected. Haynes, Chilton, and numerous websites say to disconnect and plug the advance. Seems like timing would be dependent on vacuum, and at higher altitudes like mine, since vacuum is lower, timing would be even more retarded. But just the opposite is true. I have to advance my timing more up here (6000 ft) to get good performance. Pinging is not an issue at these altitudes.

On my stock 400, with timing set at 6 deg with the vacuum connected, idle is rougher and performance is terrible. When I set the timing without vacuum advance, and then reconnect it, idle is much smoother and acceleration is much better. Are you saying that in my case the timing gear/chain set has a problem? New one on me.[/QUOTE]

My truck has a diagram decal in the engine bay with all the tune-up specs and vacuum hook-ups. It clearly says to D/P the vacuum hose when setting the timing. (disconnect and plug)

 

[Mil1ion]

I'll post the details of timing some of these engines from a bonafide source once I find it again.

Remember though this is AFTER the static timing is set.

It is the connecting of the vacuum to the V/A that will accurately tell one if all parts are working and worn parts reveal themselves

Ford lists "3" timing values in setting the timing.