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* white can: Delay valve in the Distributor vacuum advance hose



The large size of this valve suggests it is a thermo switch. They often work like this:
* At cold temps it does nothing
* At normal temps it delays spark advance, so that when de-celerating and the manifold vacuum rises, it takes some seconds for the vacuum to make it to the distributor. This prevents spikes in NOx on sudden liftoffs of the throttle (such as when shifting, or slowing down)

Note that this doesn't affect accelerating (unless the valve goes bad/get stuck) -- no effect on throttle down or full throttle power. But it can have a noticeable slight effect on driveability (throttle lift-off transitions). Just like a vacuum advance that doesn't work, it'll run fairly good, but not perfect.

Used only in Japan as far as known. USA did not use this on Datsun 1200.