Thanks for the info.
It's nice to know what that was for and that it isn't necessary.
Guess what my next project is.
Eric
Lawrie Alexander wrote:
>
> Eric........
>
> The little brass "jet" you refer to, which the notch is cut to clear, is a
> relic of the UK setup where the HIF had vacuum taken from the carb. body
> rather than the manifold. On US spec. cars, the hole beneath that "jet" is
> plugged. Ergo, the brass "jet" does nothing. Ergo, it's a heckuva lot easier
> to file off that part of the jet that intrudes into the venturi than it is
> to file a notch in a plate to exactly fit around it!
>
> So, buy new, solid plates and fit them to the carbs after carefully filing
> off the brass bits of the carb bodies that sticks up into the hole where you
> want the plates to go...............
>
> Lawrie
> -----Original Message-----
> From: Eric Zambori <eaz@snet.net>
> To: mgs@autox.team.net <mgs@autox.team.net>
> Date: Thursday, January 07, 1999 5:19 AM
> Subject: Re: Springtime Tune-up
>
> >I saw your message about simply replacing the butterfly valves with
> >those from an earlier HS4. I considered that for my carbs (AUD493/4 -
> >72 MGB) but found that the originals have a small square cut notch
> >(about 4-5 mm) at the bottom of the butterfly valve which corresponds to
> >a small jet orifice on the bottom of the carb body that sticks up above
> >the body of the carb.
> >
> >I bought some HS4 butterflies and tried cutting a notch in them with my
> >dremel tool but I didn't have much success in making equal sized notches
> >between the two valves. This means I have a tough time tuning my
> >carbs. I can balance them OK but since one of the notches is a little
> >over sized, my engine RPM is higher than I'd like because that one carb
> >lets through too much air and I have to balance the other carb to match
> >it.
> >
> >I also considered removing the spring loaded valves from the original
> >butterfly valves and soldering the exposed hole shut. I did this and it
> >came out OK but I read somewhere that a carb backfire could melt the
> >solder on these valves and I've been reluctant to install them.
> >
> >Does anybody know of a source for an HS4 butterfly valve with a notch in
> >it? In looking through my BLMC parts book for the early B's, it shows
> >one and gives a part number. (if I wasn't at work right now I'd include
> >that number) Do you think I can trust the illustration and that the
> >part number shown is actually a butterfly valve that has a notch.
> >Should I try Lawrie Alexander and/or Joe Curto? OR should I send my
> >carbs to one of them for rebuilding and have them cut notches in a pair
> >of HS4 butterflies properly or as a more drastic step, modify the carb
> >body and cut down the little jet orifice that sticks up from the carb
> >body so the regular HS4 butterfly valves fit.
> >
> >Thanks
> >Eric Zambori
> >72 MGB
> >
> >
> >
> >Andrew Errington wrote:
> >>
> >> Hi,
> >>
> >> > >>expect to see an air leak around the throttle shafts, and I'll
> >> > be sad. I
> >> > >>also plan to solder the poppet valves shut.
> >> >
> >> > When I took my carbs off (HIF4s) earlier this week, I found
> >> > the rear valve
> >> > soldered shut and the front one standard (present and functioning). I
> was
> >> > going to ask the list but forgot until this discussion jogged my
> memory:
> >> >
> >> > Why would you do this?
> >>
> >> Well, as someone pointed out, why bother: just put new discs in from an
> >> earlier model, since I'll have everything apart.
> >>
> >> The reason for me to do it is because their springiness has gone and they
> >> hang open at idle, letting air in when the throttle disc should be
> closing
> >> the throat. Not only that but they kind of flutter, which leads to a
> rough,
> >> irregular effect on the idle speed.
> >>
> >> > Also, why would someone (I assume it wasn't the DPO, was
> >> > it, Mike ? :)
> >> > hehe ) only do it to one carb?
> >>
> >> No idea. Maybe never got round to finishing the job.
> >>
> >> > Further, is this what made it hard to balance my carbs at idle?
> >>
> >> Could be.
> >>
> >> > I was going to replace the soldered valve, but maybe I
> >> > should be doing
> >> > some soldering on the front one instead. Pros/cons, anyone?
> >>
> >> Well, you can solder them shut without disassembling them. If the
> springs
> >> are weak then you should solder them or replace both of them with new
> discs
> >> with working valves.
> >>
> >> Andy
> >> (dreading his first look at the carbs when they come off...)
> >
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