Timing question again

[norske]

I know this has been beaten to death here and other forums too but can't seem to find the definate answer on this one. I have a '68 C10 with a 305 and 2004R automatic. Put in a rebuilt distributor and now have less torque so the timing is off. When I set the idle to 700-750rpm in park, should the vacumm advance be disconnected and plugged when I set the idle, or hooked up?

[norske]

Forgot this, distributor is '75-'79 HEI.

[rwolf9653]

I have always had good luck with the vacuum line disconnected if the motor is cold, connected if the motor is a operating temp.

[hchad18]

When you set the initial timing the engine should be warmed up and disconnect the vacuum advance.

[68gmsee]

You have two different adjustments to make. Idle speed and timing and as you know they can affect each other.

The idle will depend on whether you have vacuum advance attached to manifold vacuum (lower part of carb) or ported vacuum (above the butterfy valves).

I adjust the idle with the vacuum advance plugged in first.
Then I adjust the timing with the vacuum disconnected and the line to the carb plugged in if it's attached to maniflold vacuum.

Then I go back and reconnect the vacuum advance and recheck the idle speed.

I will repeat this procedure at least a couple of times until I get the idle correct and timing exactly where I want it.

[Hottrucks]

you may just want to go old school?? I find BASE timing is a great place to start!! but I find that a bump of one degree at a time will get you to the pefect timing...just short of that timing ping or hot start issues...then adjust your idle to what works for you ..I know that my idle is very low by spec (around 450/500 in drive) if you have a standard maybe a bit more like I said what works for your truck/motor