Odd timing issue
Thread Starter
Oldsmobile enthusiast
Joined: May 2013
Posts: 689
Odd timing issue
350, HEI dizzy. Just started this problem this week.
When I accelerate normally I have a stumble. I hooked the timing light up and when I give it the gas the timing mark goes backwards then goes the right way. Is this a common fixable problem caused by a mechanical problem or an adjustment?
When I accelerate normally I have a stumble. I hooked the timing light up and when I give it the gas the timing mark goes backwards then goes the right way. Is this a common fixable problem caused by a mechanical problem or an adjustment?
Registered User
Joined: Aug 2011
Posts: 4,109
X2 on Fun71's theory.
Did you remove the vacuum hose from the vacuum advance to see if the timing stops backward movement?
The stumble may or may not be timing related, try running with the vacuum advance disconnected and plugged. If the stumble stops it may be the pole piece in the distributor. If you take the distributor cap off you will see the pole piece. It has two wires going to it, the vacuum advance is mechanically attached to it and it surrounds the distributor shaft.
The reason disconnecting the vacuum advance helps to diagnose this is because the two wires going to the pole piece often get frayed where they enter the pole piece. By disconnecting the vacuum hose the pole piece will not move and the frayed wire connection does not open and close from the movement.
Is the distributor clamp tight? It could have loosened a little and let the distributor turn.
Stumbling is more often a vacuum leak or carburetor issue but try the above first and keep us posted.
Good luck!!!
Did you remove the vacuum hose from the vacuum advance to see if the timing stops backward movement?
The stumble may or may not be timing related, try running with the vacuum advance disconnected and plugged. If the stumble stops it may be the pole piece in the distributor. If you take the distributor cap off you will see the pole piece. It has two wires going to it, the vacuum advance is mechanically attached to it and it surrounds the distributor shaft.
The reason disconnecting the vacuum advance helps to diagnose this is because the two wires going to the pole piece often get frayed where they enter the pole piece. By disconnecting the vacuum hose the pole piece will not move and the frayed wire connection does not open and close from the movement.
Is the distributor clamp tight? It could have loosened a little and let the distributor turn.
Stumbling is more often a vacuum leak or carburetor issue but try the above first and keep us posted.
Good luck!!!
Thread Starter
Oldsmobile enthusiast
Joined: May 2013
Posts: 689
Im listening.
I ran it both with and without vacuum and it was the same results.
The whole engine and dizzy has less than 500 miles, just changed out the first oil change.
This problem just started a couple weeks ago.
It very well could be a gummed up carb passage but its new also!
I even changed the plugs again yesterday.
If I find out its the new carb already, that will be it for a Holley!
I think a 600 is too small in the first place but following advice of the net!
If its the carb it may clean itself out.
I ran it both with and without vacuum and it was the same results.
The whole engine and dizzy has less than 500 miles, just changed out the first oil change.
This problem just started a couple weeks ago.
It very well could be a gummed up carb passage but its new also!
I even changed the plugs again yesterday.
If I find out its the new carb already, that will be it for a Holley!
I think a 600 is too small in the first place but following advice of the net!
If its the carb it may clean itself out.
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