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Old 02-10-2018, 10:08 AM   #43
crabman
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Join Date: Nov 2017
Location: Blairsville, GA
Posts: 28
Re: HEI ignition secrets

I would like to share my experience with timing my 69 C10 396 TH400 bone stock with HEI and QJet. I read several threads and Googled the topic and did some experimenting of my own. My truck was set at 10* initial and 32* total with 20* of vacuum advice thru ported vacuum. The truck ran fine no complaints. I decided to change to manifold vacuum for the vacuum advance and immediately the truck idled smoother. I drive the truck and it was better down low and transitioning to midrange. I brought it back and bumped my initial timing to 12* for a total of 34* timing and left the vacuum advance at 20* and manifold vacuum. After all of that i had to reset the idle speed to 750RPM and the QJet was rich so I adjusted the mixture screws until I got it to idle at 750 RPM and smooth. The timing with the vacuum advance hooked up and idling at 750 is 32*. The truck is much smoother low and mid range and it starts super quick. I am a believer in MANIFOLD vacuum for vacuum advance after this experiment. After driving like this for a while I will try more initial timing and see what it does but for now it is a nice improvement.

Edit: All my timing is in by 2800 RPM
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1969 CST/10 396

Last edited by crabman; 02-10-2018 at 10:15 AM. Reason: forgot to add something
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