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tri power need help

Old Sep 10, 2015 | 12:45 PM
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Default tri power need help

my friend has a 69 427 tripower it wont idle without giving it throttle the front and rear carbs are sucking air with the butterflies closed and linkage unhooked
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Old Sep 10, 2015 | 01:04 PM
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how can the end carbs suck air with the throttle closed? do you have the wrong carbs on the ends? the throttle plates should be closed at idle and part throttle.

the linkage needs to be hooked up for this to happen, the purpose of the mechanical linkage is to ensure this happens when the accelerator pedal is released.
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Old Sep 10, 2015 | 02:54 PM
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Does the same thing with the linkage hooked up only reason I unhooked the linkage is to verify the throttle plates were closing on the end carbs they are closing but still sucking air
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Old Sep 10, 2015 | 07:02 PM
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I had the same problem with my tripower end carbs sucking air affecting the idle. Make sure the idle bleeds on the end carbs are not clogged. I removed the end carbs and held them up to a light with the throttle closed. There should be hardly any light seen. I loosened the throttle plates screws and jiggled the plates until I had the tightest fit. The outer carb throttle plates should have opposite bevels on their edges to ensure a fairly tight fit. Obviously, everything should be very clean.

My NOM BB likes alot of initial timing- 18+ degrees

Keep in mind you are dealing with 45 year old parts that have probably passed thru many hands.
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Old Sep 11, 2015 | 06:53 AM
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end and center carbs have idle circuits?
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Old Sep 11, 2015 | 07:37 AM
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Technically no. They have an idle bleed. A small hole under each throttle plate to bleed a small amount of fuel to keep the fuel in the outer bowls fresh. No adjustment whatsoever.
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Old Sep 11, 2015 | 07:59 AM
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Originally Posted by derekderek
end and center carbs have idle circuits?
yes they do, they are fixed and non-adjustable. part of the metering plates. the orifice is .076, if someone changed your end carb metering plates, it is very likely incorrect, as replacements are not drilled correctly due to inaccuracies in the original service manual specs. they say 76 jet but it is actually .076, they get drilled to .082 as that is the equivalent jet size. common problem...

also make sure the vacuum signal to the end carbs is correct, and the secondary diaphragm springs are correct, too weak or worn out and they will open way too soon, or with little vacuum.

Float level is extremely important on these as well, especially the front carb--it gets all the heat from the fan.
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