truck dist. problem

[Bandit72]

my daily driver is a 62 Dodge D-100 pickup with a 78 360 from another truck in it...it has started having a problem where it runs HORRIBLE right off of idle but will idle and rev. fine...just as long as i don't hold it at a certain rpm...rebuilt the carb. nothing, new plugs, cap, rotor, wires, points...nothing...got to messin with it tonight while i was working on the brakes and figured out if i unplug my vaccume advance it runs 110% better...what would be causing this? I don't beleive i have the adjustable vac. advance as i stuck an allen head down there and couldn't feel anything...what should i try next?

[Bandit72]

oh, i should also add that this is the 2nd distributor i've put in it..both do the same thing...with the vaccume advance hooked up i can time it so it either runs DECENT at higher rpms but won't idle, or it will idle good and not run worth a darn at higher rpms....i've checked for vaccume leaks, there is no blow-by, firing order is right.

[aifilaw]

oh, there's a number of issues here. Possible the timing could be way too advanced. Check it with a light and see what your total timing is.
Possible vacuum ports incorrect (there is an idle circuit for the vacuum advance, and regular pots which draw more vacuum as RPM's increase... its entirely possible you have those two backwards.

Let's start there.

[Bandit72]

oh, there's a number of issues here. Possible the timing could be way too advanced. Check it with a light and see what your total timing is.
Possible vacuum ports incorrect (there is an idle circuit for the vacuum advance, and regular pots which draw more vacuum as RPM's increase... its entirely possible you have those two backwards.

Let's start there.

i already tried swapping the vacuum ports, it just gets worst...(it is the factory 2 bbl carb. so there is only 2 spots for a vaccum line)

[aifilaw]

if it gets worse, then I'd assume your timing was set too much advanced, and the vacuum advance is plugged into the wrong port, because it should be worse(more advanced) at idle.
And your entire distributer needs to be twisted counter-clockwise a bit to retard the timing back to a realistic timing mark. Get a timing light and tell us what it's set at... bear in mind I've seen it once or twice where the harmonic balancer had shifted and was not reporting true timing.

[Bandit72]

i figured it out....it's got a flat cam

[aifilaw]

well... that'd cause it too ..


sucks though, means you can either swap the cam, drop the pan to get all the metal filings out of it and hope it lasts a while longer, or do a rebuild and complete cleanup

[Bandit72]

i'm pulling the motor thursday and i'm gonna tear it compeltely down, clean, and check everything out