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Old 06-13-2012, 07:53 AM
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Originally Posted by zildjian4life218
I do have the vacuum advance can going to full manifold vacuum. I heard so much about how full manifold is the way to go but I guess in my case it will help with the idle transition by switching to the ported. I wanna start looking at getting an AFR gauge. It would make tuning so much easier.
My take on what vacuum source to use, is to use what works. On most engines, using manifold vacuum- as long as the rest of the advance curve is tailored to it- will be fine, and the engine will run best that way. But there are cases (possibly like your case) where ported will work better. Now, that's not to say you can't set your engine up to use manifold vacuum. But the way things are NOW, using ported may be the better choice. Obviously the only way to know for sure is to try ported to see what the result is.

Be prepared to raise the idle speed w/the curb idle adjustment if the idle drops too much when the vacuum is switched to ported. But if the butterflies need to be opened too far to get the engine to idle, that puts the transition slots too exposed and the off idle response will suffer because of it. That usually happens w/a big cam.

So for now, I will suggest you try ported just to see if the problem is the vacuum advance dropping out. If it IS, the fix can be addressed. If it isn't, you have at least eliminated one thing from the possibilities, and you can look into other things, like the accelerator pump shooter or other carb problems, etc.
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