The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - Help a NOOB

**dmjlambert** · 08-07-2018, 08:45 PM

The detonation (or ping or knock) on my truck sounded very much like a rattle from under the hood. I could hear it while accelerating on a test drive. So I retarded by timing by a couple of degrees and took it for a test drive again. I repeated retarding the timing until the pinging was gone. I ended up at 7 BTDC and my vacuum advance gives 23 degrees of advance. I had a separate thread here on the forum about those numbers and using the timing light.

08-07-2018, 08:45 PM	#200
dmjlambert Senior Member Join Date: Apr 2016 Location: Cypress, TX Posts: 3,949	Re: Help a NOOB - A continuing saga The detonation (or ping or knock) on my truck sounded very much like a rattle from under the hood. I could hear it while accelerating on a test drive. So I retarded by timing by a couple of degrees and took it for a test drive again. I repeated retarding the timing until the pinging was gone. I ended up at 7 BTDC and my vacuum advance gives 23 degrees of advance. I had a separate thread here on the forum about those numbers and using the timing light.