The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - Seems like I have to keep advancing my timing

Dead Parrot · 08-08-2016, 06:24 PM

If your ported vacuum is about 4 at idle and your advance pot starts to add in about 5, could be the cause of your issue. You are right at the magic point where the vacuum advance starts to come in at idle. A minor increase in ported vacuum causes a increase in advance,which causes a speed up of idle. You adjust the idle slower, which lowers the vacuum, the timing falls off, idle slows down more.

Move it to manifold vacuum and set your initial timing to 10btc with the advance pot disconnected. The initial 10 + the about 12 from the advance pot = 22 which you said seemed to be the sweet spot.

08-08-2016, 06:24 PM	#11
Dead Parrot Registered User Join Date: Aug 2012 Location: Oklahoma City, OK Posts: 2,668	Re: Seems like I have to keep advancing my timing If your ported vacuum is about 4 at idle and your advance pot starts to add in about 5, could be the cause of your issue. You are right at the magic point where the vacuum advance starts to come in at idle. A minor increase in ported vacuum causes a increase in advance,which causes a speed up of idle. You adjust the idle slower, which lowers the vacuum, the timing falls off, idle slows down more. Move it to manifold vacuum and set your initial timing to 10btc with the advance pot disconnected. The initial 10 + the about 12 from the advance pot = 22 which you said seemed to be the sweet spot.