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Old 07-16-2016, 10:48 AM   #1
reknapp52
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Default Power Valves and Throttle Stops

I have a problem with a bad hesitation, stumble coming off the throttle stop. Using a Dedenbear electric base plate stop. I can cure the problem by using a power valve in the primary metering block. Any thoughts? I think most racers don't think a power valve is a good idea, for reasons of inconsistancies? I can't spell very well any more either.
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Old 07-16-2016, 10:34 PM   #2
J&S Racing
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Default Re: Power Valves and Throttle Stops

Not sure about the under carb stops but the APD set-up uses a power valve so on the stop and wide open can be tuned independent..
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Old 07-18-2016, 04:58 PM   #3
voltdr
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Default Re: Power Valves and Throttle Stops

Can you give any details about your setup?
Weight, HP, Stop-Stall RPM,
Do you use a data recorder?
Dan
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Old 07-20-2016, 03:29 PM   #4
Ken MacNicol
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Default Re: Power Valves and Throttle Stops

I run a PV with an under carb, and ran a PV with a inline for 13 years with no problems. I just like how much better they idle.
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Old 07-29-2016, 11:02 PM   #5
reknapp52
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Default Re: Power Valves and Throttle Stops

Put the power valve back in, and all seems to be good. Not sure how other racers get by without having one with a baseplate T-Stop. What might work even better is to drill the T-stop plate to provide manifold vacuum to the secondary power valve and use one there instead of on the primaries.
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Old 09-01-2016, 05:04 AM   #6
gnicholson
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Default Re: Power Valves and Throttle Stops

Are you just installing a power valve or are you pulling 8 to 10 jet sizes when you install it? If youre just installing the valve then you are richening it up about that many jet sizes at wot. Have you verified you have the correct full throttle fuel mixture?
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Old 10-03-2016, 11:24 PM   #7
sst7250
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Default Re: Power Valves and Throttle Stops

Never used a power valve and never had a stumble coming off the stop. Amazing how many ways there are to do this stuff..BTW good to hear you have the car back out again...
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Old 04-20-2017, 10:21 PM   #8
nomad
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Default Re: Power Valves and Throttle Stops

Thought I'd add something to the conversation. If you have a data recorder then you'll get a handle on this PV thing pretty quick. I run an O2 in the #1 pipe and the #8. It gives me an idea of what's going on at both "ends" of the engine. Thus, I can have equal O2s at each end. Plus, I track manifold vacuum.


We've worked out what primary jet gives us the cruise O2 we want (because the PV is closed here, so it doesn't contribute fuel). We use the PVCR size to give us the WOT O2 to match the secondaries. Thereafter, necessary jet changes involve the rear jets and the PVCR but, not the primary mains.


The data recorder will tell you exactly when the PV opens and you can tailor that to your needs.


It's not hard to do but, just seems so here because I'm not really a wordsmith.


BTW I run an in line stop.
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Old 06-29-2017, 01:47 PM   #9
sst7250
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Default Re: Power Valves and Throttle Stops

An inline stop ads another element to the pot, in that you get pump shot everytime the stop opens, unlike in an under carb set up. I do understand your theory but with the added pump shot in the mix cannot imagine a stumble unless it was dead rich, which is hard to do. On an under the carb stop I can understand the use of a PV. I would like to see more info from the OP on the issue he has. IE carb size and set up
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