A few more things you can check on.
The first thing to do is the basic tune up stuff. Excellent points, dwell,
timing, plugs, wires, cap and rotor are critical. There must not be any
vacuum leaks. On a 30 year old car, it's a good idea to just replace all of
the hoses making sure you use the right diameters. Next, adjust the valves.
The carbs are the first thing to be erroneously mucked with on an MG when it
is really an ignition, valve or vacuum fault.
Then, the correct initial setting for an HIF is to lift the piston so you
can see the jet. Raise the jet to the point that it is flush with the
bridge. A small metal ruler gently placed across the jet well can help you
judge this. Then adjust the screw clockwise (richer) two full turns which
lowers the jet in the well. Adjusting it to a 1/16" above the bridge as you
were advised will be much too lean.
And, if it started running poor after your adjustment, and you have
reinstalled the air cleaners, check to make sure that you installed the
aluminum air cleaner housing adapters and gaskets right-side up. There are
four holes. Two are for the bolts and two are ambient-air pressure sense
holes for the vacuum dome. The two air holes should be placed above the
bolt holes. If it is installed upside down, the air holes will be blocked,
and the pistons may not raise at all under power. It will idle though.
This is a common mistake and a good thing to check.
On the 72 MGB that I just bought, one of them was upside down. It appears
that it has been this way for many, many years. It sort of ran, but
seriously lacked any "snap". I just ordered the parts to do a rebuild on
them. It appears that after sitting idle off and on for so many years,
there is something gummed up that is preventing me from adjusting them
properly. I should begin this in a week when the parts arrive. I'm very
curious to see what they look like inside.
From: email@example.com [mailto:firstname.lastname@example.org]On
Behalf Of Zach Dorsch
Sent: Friday, March 08, 2002 12:57 PM
Subject: Help HIF4 Balancing/Tuning
Well I went ahead and tried to adjust the carbs. I
thought that I understood the directions, but I guess
not. I first tried adjusting the adjusting screws
because the car was running rich. This was after I
had loosened all the clamps for the throttle
interconnection. I was going by the manual and by the
instructions for the Unisyn. It didn't run very well
after that, so I stopped by an import shop around here
today. I wanted to find out if there was maybe a
baseline for what the needles should be set at. He
told me that they should be about 1/16" above the
bottom of the opening of the intake on the carb (hope
that makes sense). THen the car wouldn't run without
the choke on. So I tried readjusting those back down
to where they were, and now it backfires when I rev
the engine. This is my first attempt at this.
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