Ignition Timing changing with temperature

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Ignition Timing changing with temperature

Post by breezerabbit »

Hi All

I have a '65 110HP car, and setting the timing is like chasing a moving target. Has anyone else any experience of the timing apparently changing with temperature? Harmonic balancer has not slipped. Presumably a worn distributor, but before I tear into it maybe there is something I have overlooked. Glad of any associated wisdom. Thanks.



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Re: Ignition Timing changing with temperature

Post by bbodie52 »

Is your distributor fitted with an electronic breakerless ignition system, or is it stock with ignition points?

Are you disconnecting the vacuum advance tube from the vacuum advance and plugging it before setting the timing? It must be disconnected and plugged to properly set the timing at idle.

Is the engine warmed up to operating temperature with the chokes fully disengaged when setting the timing? What is the idle speed when setting the timing? Timing setting: 14° BTDC @ 500 RPM. The centrifugal advance begins to advance the timing at 800 RPM, so if your idle speed is close to 800 RPM the centrifugal advance mechanism may be affecting the base timing reading you get with a timing light.


If you are running ignition points, did you verify the dwell with a dwell meter and did you inspect the condition of the electrical contacts to ensure no pitting or burning of the points before setting the timing?

Is the centrifugal advance hose connected to the vertical spark port on the right carburetor? (Not the horizontal manifold vacuum port that is reserved for the choke vacuum break mechanism).

If you are still running ignition points and you also suspect your 55 year old distributor is suffering from excessive wear, you might want to consider upgrading to a new Stinger distributor that includes an electronic breakerless ignition system. Doing so will improve reliability and greatly reduce tune-up maintenance on your car. The cost of adding a Crane Cams [FAST] XR700 or a Pertronix breakerless system to your aging distributor, and overhauling/reconditioning that distributor will generally exceed completely replacing it with a new Stinger distributor.

:link: viewtopic.php?f=225&t=15101


1965 Corvair Chassis Shop Manual Distributor Specifications.jpg
1965 Engine Tune Up Chart.jpg
Brad Bodie
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Re: Ignition Timing changing with temperature

Post by joelsplace »

Maybe a broken key on the balancer or a broken roll pin on the distributor gear?
If it is the balancer key the timing won't actually change but it will appear to. If it is the distributor gear the timing will actually change.
114 Corvairs, 5 Ultravans and counting
Northlake, TX

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