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cppursell · 01-21-2012, 05:59 PM

After disconnecting vacuum, I set my initial timing at 8 adv. 3000rpm takes me to 27 adv total. I drove it and it pings at WOT and under heavy acceleration.

I hooked up manifold vacuum, and have an idle timing of 32, and 52 at 3000rpm. It seems to idle better but driving it pings easily.

I read that manifold vacuum is necessary)(http://rockridgefarm.com/vettdoc/Timing_101.pdf) "...you need vacuum advance, connected to full manifold vacuum. Absolutely. Positively."

But I've heard from others including that mechanic that you need ported. Also, here (http://www.73-87.com/7387garage/drivetrain/hei.htm) gives tips on setting timing with an adjustable vacuum can.

I'm so confused!! What is right?!?

01-21-2012, 05:59 PM	#3
cppursell Registered User Join Date: Dec 2008 Location: San Francisco, CA Posts: 144	Re: Vacuum advance issues After disconnecting vacuum, I set my initial timing at 8 adv. 3000rpm takes me to 27 adv total. I drove it and it pings at WOT and under heavy acceleration. I hooked up manifold vacuum, and have an idle timing of 32, and 52 at 3000rpm. It seems to idle better but driving it pings easily. I read that manifold vacuum is necessary)(http://rockridgefarm.com/vettdoc/Timing_101.pdf) "...you need vacuum advance, connected to full manifold vacuum. Absolutely. Positively." But I've heard from others including that mechanic that you need ported. Also, here (http://www.73-87.com/7387garage/drivetrain/hei.htm) gives tips on setting timing with an adjustable vacuum can. I'm so confused!! What is right?!?