Dual Diaphragm Distributor

Q: Dual Diaphragm Distributor

I am having a problem with a slight backfire and someone told me to disconect one of the two hoses to the distributor. Is this correct?

A: 68 was the only year for a dual diaphragm (advance /retard) distributor. It was to retard the distributor under certain conditions for emission lowering. A service bulletin was issued for dealers that got complaints to disconnect the retard side. A lot complaints of a slight backfire on coasting downhill and deceleration . Such a tech service bulletin wouldnt be issued today as theres a stiff fine for modifying or removing any emission device Chances are the retard side has been disconnected on yours. Look for a separate vacuum hose nipple on the distributor advance/retard control “thingy”.If its been removed,hope that the vacuum source has been plugged off.

From the Pontiac Service Information Bulletin:

[pdfjs-viewer url=/dtb/docs/68-T-2.pdf viewer_height=800px fullscreen=true download=false print=true]
[pdfjs-viewer url=/dtb/docs/68-T-2A.pdf viewer_height=800px fullscreen=true download=false print=true]
[pdfjs-viewer url=/dtb/docs/68-I-45.pdf viewer_height=800px fullscreen=true download=false print=true]

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