Why.

[the_boozer]

sorry to thread crash but can 1 of you blokes tell me why the vac advance needs to be disconnected to set the timming?
Its vacuum supply is ported so it doesn't get any vacuum until the throttle is open.
Are v8's like the 6's and the timing mark moved? That happen on the blue 6's early in the run of blue motors.

 

[EYY]

sorry to thread crash but can 1 of you blokes tell me why the vac advance needs to be disconnected to set the timming?
Its vacuum supply is ported so it doesn't get any vacuum until the throttle is open.
Are v8's like the 6's and the timing mark moved? That happen on the blue 6's early in the run of blue motors.

They're not always connected to ported vacuum. A lot of the time they're connected directly to manifold vacuum. Under load, manifold vacuum drops and retards the timing to prevent pre ignition. It's basically concerned with fuel economy, emissions and driveability.

In any event, disconnecting it makes sure that the dizzy isn't advancing at all and giving you false readings to base your timing off.

I'd assume the OP has overlooked something that's already been mentioned, or has timed the cam incorrectly. There's not really much that you can stuff up on these engines. What is the total timing in the distributor op? Did they tell you what to set the base timing at when it was regraphed? Are you absolutely sure that you're not trying to set the timing on TDC of the exhaust stroke? That would mean that you're trying to set the timing 180 deg out.

 

[the_boozer]

They're not always connected to ported vacuum. A lot of the time they're connected directly to manifold vacuum.

Can you tell me 1 vehicle made after 1976 that has the vac advance connected to the inlet manifold?

 

[EYY]

Can you tell me 1 vehicle made after 1976 that has the vac advance connected to the inlet manifold?

I'll let you do the research. Most may not have come from the factory that way, but full manifold vacuum is considered to give better idle quality and cooling at idle. I've done it to my cars in the past. It's not that hard to block the vac line anyway to set the timing once in a blue moon in any case.

I'm not sure about the holden tvs', but many actually start out with manifold vacuum advance which switches to ported vacuum advance as the tvs changes position as it warms up.

 

[the_boozer]

I'll let you do the research.

Stick your research, See you cant name 1 either.Most manual holdens didn't allow vac advance unless in top gear . The tvs puts full vac on the advance to speed the fan up if the motor is over heating.

 

[EYY]

Stick your research, See you cant name 1 either.Most manual holdens didn't allow vac advance unless in top gear . The tvs puts full vac on the advance to speed the fan up if the motor is over heating.

Precisely.............

 

[Not_An_Abba_Fan]

Did you set the cam up on number 1 TDC or number 2 TDC? Easy mistake to make, number one is right hand front of engine when viewed from the back, or front left when viewed from the front.