Matt,
After my round with the HIF's, no vacuum port and all, I went the MG
Tech. bulletin board and searched for HIFs there. It seems according to the
thread there that the HIF's did have that vacuum port in the UK market, but
that the US cars didn't. Something about them trying anything to get around
the emissions legislation. They also described how to modify the US HIF to
incorporate the vacuum port, and it basically drill out that plug you found
and with and bit a few thou. less than the size of the brass tubing you wish
to insert, and press in the tubing. The hole should not be drilled through,
just enough to hold the tubing, then a small (0.020") hole drilled through
to the venturi area in the appropriate place just slightly upstream of the
closed throttle plate. Result is no vacuum at idle, vacuum during
acceleration drifting back to no vacuum at full throttle. It's supposed to
help the part throttle horsepower and acceleration, but probably doesn't do
a thing for the emissions.
I'm going to try this on mine this weekend and see what happens. It'll
either be a cheap fix if it works or an expensive one if it doesn't.
Harlan.
-----Original Message-----
From: Kulka, Matt <Matt.Kulka@hboc.com>
To: MG List <mgs@autox.team.net>
Date: Friday, October 09, 1998 7:23 AM
Subject: RE: HIF Carbs & Ported Vacumn
>I saved this message of Harlan's because my '74 B is running manifold
vacuum
>to the distributor. I found the diagram in my Haynes which shows the
vacuum
>fitting on the bottom of the rear carb, but couldn't find it on the carb by
>feeling around. So last night I pulled the darn thing clean off the car,
>flipped it over, and what do you know, but there's some sort of brass plug
>in that hole. Inside the carburetor bore, the top of that plug is hollow.
>Either the brass nipple was very professionally changed with a
>thimble-shaped plug, or the original nipple was very effectively broken off
>and hammered flush.
>
>Can anyone shed some light on this? Is my '74 supposed to run on manifold
>or ported vacuum advance? Is this plugged vacuum hole normal? If I'm
>supposed to run ported, and am using vacuum instead, will this affect
>anything besides engine temp. and emissions at idle?
>
>As always, thanks.
>
>Matt Kulka
>'74 B
>
>> -----Original Message-----
>> From: Harlan Jillson [mailto:hjillson@argolink.net]
>> It also had it's original HIF carbs., and had the vacumn
>> advance plumbed to the manifold vacumn. Now
>> everyone knows that is backward from what you need...
>
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