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

[norske]

Idle at 700rpm with vacumm advance disconnected and plugged? Moderator, sometimes not recognized as logged in, have to do it like three times.

[cdowns]

the whole key in timing an engine is to set TDC accuratly b4 you start//with aid of piston stop is the best way i've found and it's also very very handy to have a service manual

[norske]

When I put the diz in, I put my finger over the number one hole, bumped the starter and felt the air coming up on compression, looked for the timing mark, bumped it again and it landed right on 0 deg. on the scale. Is that lucky or what? Put in the diz and the rotor was pointing right at number 1 where I marked it. it runs great, just lost power.

[Hottrucks]

pointing at #1 gets it close enough to run but I would bump the timing..your marker maybe off a degree or a coulpe??? thats why its nice to just bump it to that Sweet spot..knowing where TDC is is a great idea but depending on your fuel ( we all know that fuel changes from area to area and sometimes from station to station ) I tend to fuel the same place most of the time for what thats worth?? another thing that will effect it is your altitude...you have to remember that when GM puts a # out there it has to work everywhere on any fuel and in 19?? fuel specs as we all know are a little different.......Look for the sweet spot

[cdowns]

Originally Posted by norske

When I put the diz in, I put my finger over the number one hole, bumped the starter and felt the air coming up on compression, looked for the timing mark, bumped it again and it landed right on 0 deg. on the scale. Is that lucky or what? Put in the diz and the rotor was pointing right at number 1 where I marked it. it runs great, just lost power.

that might b close but you can still be off a number of degrees//it's not accurate

[norske]

Right now set at 10 degrees BTDC at 700rpm with vacuum advance unhooked. Will bump out 2 at a time.

[71tahoe]

Usually this suggestion has been thrown out already. Did you just hook up your old wire or did you run a new dedicated 12v from ignition unfused at the fuse block? The old wire doesn't provide 12v and it will affect performance.