Re: [T3] cutoff valve

["Brad" <BnPWOOD2@att.net>]

Steven,
    Thank you for the input.  And, thank you for the clarifications on a few
things.  I wasn't really thinking that "backfiring" is really a popping back
through the carb, I guess it is.  What I am getting is definitely fuel
burning in the exhaust.  While working the throttle from behind the car, I
saw fire shoot from the right hand pipe.
    As for the idea that a mixture that is too rich can cause this problem,
I think that has merit.  My mixture has been too rich from day one.  I also
see a bit of fuel leaking intermitantly from around the shafts for the
butterfly valves.  It seems to me that all the adjustments in the world will
not help if fuel is gushing from leaks instead of needle valves.
    In a previous post, you kindly replied that I could get the bushings
replaced but a good machinist, and that I could get rebuild kits for the
stock carbs.  Is the bushing rework simply a matter of reaming out the old
and pressing in new?  Are the new bushings part of a rebuild kit?  Where
might I obtain these rebuild kits?  The local shop here is not as expert at
type 3's as they are about the beatles.   I was hoping to get through the
summer and do carb rebuilds over the winter, but I am not sure if this will
work out.  I gues I can start as you and Jim say, and look for the low
hanging fruit in the way of something that seems out of place, loose, or
missing.
    I welcome you input.

    Also, I am still not certain if I have the right cutoff valve.  Should a
55 work in place of a 5?  The 55 has smallet holes on the sides, but it has
4 as opposed to the 3 on the 5.  If I need one, where can I get one?

Thanks,
Brad




----- Original Message -----
From: "Steven Ayres" <comwest@att.net>
To: <type3@vwtype3.org>
Sent: Sunday, August 03, 2003 12:49 PM
Subject: Re: [T3] cutoff valve


> Brad=> The right hand pipe is still backfiring.
>
> As I often do, I have to first clarify that what you're getting is
> postignition (unburned fuel igniting in the exhaust -- small pop) rather
> than backfire (fire in the cylinder coming up through the carb -- big,
scary
> explosion).
>
> Postignition is not unusual, and often points to an exhaust leak. Fuel in
> the exhaust can indicate that the mixture is rich, spark timing is off, or
a
> valve isn't set right. So yes, it could be a carb problem, but I agree
it's
> not likely to be the cutoff valve.
>
> From your description I'll concur with Jim that all the rattling around
> could easily have messed you up. Compare your carbs and look bits that are
> missing or loose.
>
> => There are 2 "pipes" that are part of the 2 piece housing
> => around the main fan.
>
> Known as 'heat elbows' and 'fan shroud.'
>
> => The right hand plug is gone from the housing.
>
> These normally go to the heat exchangers and air ordinarily flows through
> them. Yes, having one wide open gives you less cooling air, but not as
much
> less as you might think.
>
> => Is it possible that I have a valve sticking or burned
> => that is causing this problem?
>
> A burned valve would cause a consistent loss of power -- in essence you
lose
> compression on that cylinder. A sticking valve would produce the same
result
> intermittently, and could push fuel mixture into the exhaust. But this
> condition won't likely come on suddenly.
>
> Steven Ayres, Prescott AZ
> '66 Big Ghia
>
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