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Old 05-07-2012, 07:42 PM
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cobalt327 cobalt327 is offline
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Basically you want the secondaries to open as soon as they can w/o causing a bog.

A lot will be found in the timing curve I believe. Even fine tuning the accelerator pump circuit to give a seamless transition from idle/low rpm to wfo will help. Get the timing sorted first, then work on the carb tuning.

If the vacuum advance is supplying a lot of timing- timing that is dropping out when you hit the throttle- that can cause a bog, especially w/a stick shift car. An AT car having a correctly matched TC will flash to a higher rpm at the hit of the throttle and that will lessen or eliminate the effect of vacuum advance timing going away, because the mechanical advance is able to compensate for the loss of vacuum advance almost instantly because of the TC stall rpm. In a manual trans vehicle this is delayed from happening until the rpm gets high enough for the mechanical advance to compensate for the loss of vacuum advance- hence a bog/hesitation.

The cure for that is to use more initial timing, and to use ported vacuum for the vacuum advance or less vacuum advance and manifold vacuum. Limit the vacuum advance to 10-12 degrees and use an adjustable can so you can set the tip in point. In most cases the mechanical advance will need to be limited to keep the total (initial plus mechanical) from being too high.

Last edited by cobalt327; 05-07-2012 at 07:55 PM.
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