modifying holley 4160 carb for off-road use

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nospam@dontspamme.com - 17 Dec 2004 06:41 GMT

Hello,

I have a couple of questions related to using a holley 4160 in an off-road
application. In particular, I'm using the carb on a sandrail, and environment
which is both dirty (lots of sand getting into everything), and subject to a lot
of bouncing around.

First of all, can someone explain to me what the little rubber flipper thing on
the top of the primary float bowl is for? Apparently it is open during idle, and
closes as soon as the throttle is opened. The obvious answer is that it is a
vent for the fuel bowl. However, the bowl already has a vent.... So I'm confused
why this flipper thing is there as it seems an excellent place for sand to sneak
into the fuel bowl.

Secondly, I was wondering if anyone has experience using the off-road needle and
seat assembly that is spring loaded. Right now, I have some trouble with fuel
sloshing out of that irritating flipper thing, and I'm hoping the spring-loaded
needle and seat might solve the problem.

Lastly, are there any other recommended mods for off-road and.or sandy
conditions?

Thanks,
Scott

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Mike Romain - 17 Dec 2004 14:39 GMT

I can help a bit. That rubber vent cover usually leads to a charcoal
canister, the same place the gas tank vent is supposed to go. This is
for fume collection when it sits. The canister is supposed to purge the
fumes when the engine comes up to speed and is hot.

It is a great place for sand to get in also. I am speaking from
experience from running it open while waiting for a replacement
canister. If you are running with no canister, then I recommend a line
on this vent with an inline gas filter on it to keep the dust and sand
out.

I also have been told to use 'any' carb except a Holley for off road
because of the float issues you are experiencing. Spring loaded needle
or not, when the float drops, gas flows.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

> Hello,
>
[quoted text clipped - 20 lines]
> Thanks,
> Scott

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Neil Nelson - 17 Dec 2004 14:54 GMT

> Hello,
>
[quoted text clipped - 14 lines]
> sneak
> into the fuel bowl.

That vent is to keep the engine from being overwhelmed by fuel
vapors at idle.
The vent you describe is often only found on Holley carbs that
are OEM, many aftermarket Holley carbs don't have them so you can
probably plug it off or replace the bowl with one that doesn't
have it. new Holley bowls are about $30.

> Secondly, I was wondering if anyone has experience using the off-road needle
> and
> seat assembly that is spring loaded. Right now, I have some trouble with fuel
> sloshing out of that irritating flipper thing, and I'm hoping the
> spring-loaded
> needle and seat might solve the problem.

It may help, disabling the bowl vent at the top of the bowl and
extending the vents at the top of the airhorn will probably do
more though...

> Lastly, are there any other recommended mods for off-road and.or sandy
> conditions?

A vent whistle may help also.

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