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Thread: Power Valve Gasket Question

  1. #1

    Default Power Valve Gasket Question

    My '63 Polara has a 413/426 with 440 ported heads, 727 push-button auto with kit, and what I think is a 509 Mopar cam. So at idle I have 5 inches of vacuum. I ordered 2.5, 2.5, & 4.5 power valves to test changing them out, but when I went to remove the current 6.5 valve in the Speed Demon 750 vacuum, I see that it did not have a gasket (only an o-ring), and that it's a high-flow (?) valve with 4 ports? I had ordered standard valves not knowing that the Speed Demon had high flows in it. While I wait for the high flow valves to arrive that I ordered here yesterday, my question is if the valves only come with the paper gasket do I just keep and use the existing o-ring?

    The carb idles great thanks to the Idle-Eze (which is why I bought the Demon), but I have constant stumble/surge from a stop to when it shifts to second, then from second to third. Even after it has gone into drive, it's not smooth until highway speeds. Accelerator pump looks correct, primary transfer slot is .20", secondary slot right at the edge per manual for cars idling under 1000 RPM, so I'm probably assuming incorrectly that this is an issue with transition from idle circuit to mains and the most likely culprit is the power valve?

    If anyone can offer other tips not found elsewhere in this forum, I would appreciate it. Went from a Street Demon to Speed Demon because the Street Demon idled way rich, because I had to open primaries too far to compensate for low idle vacuum and make it idle at all. Thanks, Forrest

  2. #2


    Did some looking around and it looks like Demon & Holley don't make 4 port power valves, but Quick Fuel does. So why would I have purchased a brand new Speed Demon 725 from Summit and it have a power valve in it from Quick Fuel?

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