Booster venturi problem

Booster venturi problem

Joined: January 30th, 2010, 6:16 pm

February 28th, 2010, 1:12 pm #1

Boosters seem to be a hot topic of late. Anyone have any advise on how to center the inner part of the emulsion tube on the booster venturi? None of mine are concentric (see pictures).

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In fact one of the inner tubes on the primary side appears to be blocking some of the outer tube holes.

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When I try to bend the inner tube, it just springs back into place. Any ideas?
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Joined: October 25th, 2008, 11:14 pm

February 28th, 2010, 7:59 pm #2

I have wondered the same thing with my 4100. Like yours, the inner tubes in my emulsion tubes are not installed in the center of the tube, though mine are not laying directly against the wall of the outer tube covering any of the little holes on the side either.

It is one of those things that make me wonder if it was intentionally offset because that is how the booster is calibrated or if it is out of alignment because it just does not matter or of it was just lackadaisically assembled/installed. There are soo many "little" things about these carbs I would love to know better about this being one of them.

It would be interesting to know the general consensus regarding this from other people too. Are all of them off center or do some people have boosters with them installed directly in the middle? Does it really matter where they are? I'd love to know.



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Joined: May 18th, 2005, 4:01 am

February 28th, 2010, 10:13 pm #3

...at my CH and A boosters. They are the same way. I stuck a numbered drill down the tubes to see If I could better align them and they just sprang back to off center.
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Joined: January 30th, 2010, 6:16 pm

February 28th, 2010, 10:49 pm #4

that the booster assemblies would have to be taken apart (or at least the outer tubes) in order to straighten the inner tubes. I'd like to know if anyone else has tried that.
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Joined: May 18th, 2005, 4:01 am

February 28th, 2010, 11:35 pm #5

...considering they all, so far, seem to be that way. Additionally, I would be afraid of ruining the outer tube by trying to twist it out.
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Joined: January 30th, 2010, 6:16 pm

March 9th, 2010, 9:38 am #6

Has anyone ever taken a booster assembly apart? It looks to me like the emulsion tubes might be inserted from the top of the assembly. Are they press fits or do they just drop in? Anyone have a source for the plugs that seal the boosters? I might have to take a junk two barrel booster apart to find out.

Roy Simkins
'67 G.T. 500
'66 G.T. 350
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OldSkool
OldSkool

March 9th, 2010, 2:29 pm #7

The tubes are pressed in from the bottom. If you are careful and lucky you can twist \ rotate them in place, however you may end up crushing the tube as well.
To do it properly I would send just the booster off to KP Carbs (carbontooters) and ask him fix it.
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Joined: January 11th, 2010, 4:03 pm

March 9th, 2010, 2:36 pm #8

...considering they all, so far, seem to be that way. Additionally, I would be afraid of ruining the outer tube by trying to twist it out.
Like getting the timing spot on, good plugs and wires and getting the A/F ratio correct on a dyno. Those would pay off much more performnce than tweeking a tube.

Duke
66 Sunbeam Tiger
Fort Leavenworth, KS
Last edited by 66SunbeamTiger on March 9th, 2010, 2:37 pm, edited 1 time in total.
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Joined: May 29th, 2007, 7:25 pm

March 9th, 2010, 2:43 pm #9

Boosters seem to be a hot topic of late. Anyone have any advise on how to center the inner part of the emulsion tube on the booster venturi? None of mine are concentric (see pictures).

[/IMG]

[/IMG]

In fact one of the inner tubes on the primary side appears to be blocking some of the outer tube holes.

[/IMG]

When I try to bend the inner tube, it just springs back into place. Any ideas?
Greetings all,


There is no need to worry about the inner tubes being mis-aligned. Those inner tubes are the idle circuit feed tubes, and the necked down section at the bottom forms the idle feed restriction, or jet. Idle fuel is drawn from the main well through the idle jet and emulsified with air from the main idle bleed. The main idle bleed is located high up on the booster assy, facing inward towards the throttle bore.

This very rich air fuel mixture then moves outboard, at a downward angle towards the idle down passage. The brass restrictions you see in the outermost holes of the booster assy is the idle channel restriction. It's function is to limit the total amount of the rich air fuel mixture delivered to the engine through the transfer holes just above the throttle plates. After the emulsion passes the idle channel restriction but before it enters the idle down passage in the main body, additional bleed air is introduced through an angled passage drilled from the outer edge of the booster assy. This bleed also act as siphon breaks which will cause fuel flow to stop once vacuum in the idle circuit drops below a calibrated level.

Thus endeth idle fuel flow through the booster assy. Further trimming to the idle fuel flow occurs at the transfer ports in the main body, but that is outside this examination of booster fuel flow.

Note, both primary and secondary boosters have idle systems, but as a rule, secondary boosters do not have idle channel restrictions. I will go into the reason for this in a future posting.


As you are most likely aware, this circuit handles the fuel delivery for more than just idling. Small changes here make a big difference in the fuel delivery to the engine. Stay tuned for more information on the function of the various tubes and restrictions contained in the booster assy.

Don
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Anonymous
Anonymous

March 9th, 2010, 11:20 pm #10

ive noticed some boosters do not have the idle feed restrictors, the air bleed is not drilled and the tubes dont neck down on the bottom. I assume these would cause a rich idle circuit.
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