Vacuum advance

[Jabes1]

I think I see what you're trying to say. That setup could run more efficiently than it does. If you want a factory tune, sure set it up that way, but with todays gas prices why not set it up to run as efficient as possible and get more from it? His truck isn't exactly stock especially with that Edelbrock Carb. Tom Langdon from Stovebolt does amazing things with these I6's. I don't think you understand exactly what the function of Vac Advance does or its initial purpose. Here's one of Landon's tech tips from his site http://stoveboltengineco.com/2002/04/vacuum-advance/ its pretty basic. There was a really good article not long ago where someone was having a stumble and the truck wasn't accelerating like it should. Landon recommends initial timing at 15-18 degrees advanced with the vac can unplugged and then running the vacuum can at full manifold vacuum. Needless to say it really woke the truck up. I wish I could find the article! You definitely know your I6, but I think we all can learn something new every day.

Stock cams produce more vacuum than performance cams. Lean mixtures need more ignition lead to ignite than rich mixtures. Idle is a low load, high vacuum lean mixture. Cruise is high vacuum, low load, lean mixture as well. I'm sure his I6 will idle real low if he wants it too, but it takes a lot to get that carb to start sipping off of the power circuit. It would totally have to be setup incorrectly. The vac can will raise the idle and smooth it out when hooked up to full manifold vacuum as it should, he can then adjust the idle to where he wants it, hook up a vac gauge next and then adjust the screws the same amount to achieve the highest vacuum at idle.

Higher compression and a big cam have low vacuum and most people with those setups have nice heads that burn the mixture very efficiently which require less advance to burn. I've set up a few Edelbrocks/Carters to run on stock mills to blown mills and I've found that idle is set up in the same manner for both. His truck will run better and more efficient with the vac can hooked up to full vacuum. Ultimately its his truck, his decision. Nice truck geezer#99, looks clean!