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#1
01-29-2020, 07:42 AM
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RPM has nothing to do with vacuum production falling off far as manifold or ported. Light engine load produces high vacuum. Vacuum changes or drops off quickly with increased throttle angle/engine load. The harder you load the engine the less vacuum is produced. At very heavy and full throttle the vacuum available above and below the throttle plates is pretty much the same, or zero.
ALL sources below the throttle plates will show basically the same readings and operate the vacuum advance in the same fashion. This includes the "Tree" in the rear of the baseplate or any other source in the intake manifold.....Cliff
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If you can read this, thank a teacher. If you can read this in English, thank a Veteran! https://cliffshighperformance.com/ 73 Ventura, SOLD 455, 3740lbs, 11.30's at 120mph, 1977 Pontiac Q-jet, HO intake, HEI, 10" converter, 3.42 gears, DOT's, 7.20's at 96mph and still WAY under the roll bar rule. Best ET to date 7.18 at 97MPH (1/8th mile), |
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#2
01-29-2020, 01:31 PM
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I would avoid using a source on a single runner for the ignition vacuum advance, like the one on the #1 runner on a Pontiac intake, as the signal pulsates and are somewhat weaker than any plenum source under the carburetor throttle blades.
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