Just installed rebuilt 351 w in 1984 F150. New Edlebrock 1405 carb and Preformer intake. Set timing to 10 degrees, when I reconnect vacuum line to distributor timing marks go to 35 degrees and idle jumps up to about 1000 rpm from 800 rpm, can not get idle down below 1000 rpm, no matter what.
Also seems to have a miss with vacuum attached. Will not be running on road for couple weeks until body is complete, any comments concerning the timming. Has a late 1970's ignition all emmisions and computer gone.

 

maybe the vacum advance is advancing to far and cause it to fire at TBC and speads up the engine i had this problem on my chev 350

 

Try connecting the vacuum advance to "ported" vacuum. That's the port on the carb that doesn't have vacuum on it at idle but does as soon as you crack the throttle.

 

Thanks I will try it, How much advance would be normal.
I know Ford had heavy springs in their distributors, I will driving the truck next week to see if there is a problem or not.
Part of my miss was from the secondaries on the carb were cracked open just enough to put fuel in, thus causing high idle.

 

The fun part about timing advance is that it works on a curve. That means that at idle, you'll have one setting and with just about every increase in RPM and throttle opening from that, the timing changes. The tricky part is figuring out the curve that works the best for your engine combination. The factory had it set up one way but if you do any modifications, the proper curve will be something different. From the base idle timing (static timing, the setting you set at idle with the vacuum advance disconnected) the advance will increase with throttle (vacuum, when connected to a ported supply) and also with RPM (mechanical). If the vacuum advance canister is adjustable (some are, some aren't) that's great. You can easily tinker with different settings to see what works. The mechanical advance is adjusted with different weights and/or springs in the distributor (under the breaker plate, a little harder to get to).
Most (basically stock) engines like to see around 38° total advance (static + vacuum + mechanical), all in by about 2500 RPM. Vacuum can be connected to either a ported or manifold vacuum source. Where you set everything will depend on what the engine likes and how you intend to use it.
Short of running it on a dyno, watch for hard starting when warm (kicking back against the starter, too much initial) or pinging under a load (too much vacuum and/or mechanical).
Hope this helps.
Greg

 

Thanks for the lesson on timing, I will see what works best for me. My main concern was doing something wrong and having damage done to a new motor.