boost and vacuum advance

latamud · Jul 7, 2004

Hello,
I'm running 9 lbs boost on my 289 with a mechanical(cetrifical) advance distributor. I am going to drop in a 351w and will use a duraspark distro. I can only find duraspark distros with the vacuum plunger attached to it. Can I just plug the vacuum port and depend on the internal mechanical advance mechanism in the duraspark? Even if I ran a vacuum line from the carb to the distro, the boost would keep the vacuum plunger from advancing. Is the mechanical advancement enough to keep the engine in performance?
Thanks,
bart

ForceFed70 · Jul 7, 2004

Yes, just don't connect the vacum advance.

With a boosted setup, I would seriously going to a digital ignition system that will allow you to use a BTM (Boost timing master) basically this unit does the opposite of the vacum advace. It retards the timing based on how much boost is applied.

TobyGaff · Jul 7, 2004

Vacuum advance typically only works at the lower end of the rpm range, where you typically will not have a lot of boost. By the time the boost comes in, your centrifigal advance should be kicking in. I would think that you would have enough adjustment in the vacuum advance to tune it to make it run just fine. Although an electronic ignition would be better, I think that you could make this setup work.

latamud · Jul 7, 2004

Thanks guys,
I'm running an MSD BTM with this setup and it will retard at boost.

boost and vacuum advance

latamud

ForceFed70

That's why they call it "dope"

TobyGaff

latamud

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boost and vacuum advance

latamud

ForceFed70

That's why they call it "dope"

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latamud

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