On Thu, 2 May 1996, Allen W. wrote:
> Have HIF4 Carbs on my 74-MGB. Has rebuilt engine with 8.8:1 pistons and
> upgraded cam. Runs great all the time and idles great most of the time.
> Can set idle @800 rpm and it will stay there for some random period of time.
> Then it will drop to <500 rpm and nearly quit running. This usually occurs
> after warmup. Floats and needles seem OK(carb rebuilt < a year ago). Can't
> find any vacuum leaks. I need some suggestions. Thanks to all.
I believe the HIF4's have a bimetal screw which is temperature sensitive.
It's in the Doohicky which adjusts the main jet. When the car is warmed
up, it leans the mixture back. I think there is another temperature
sensitive Doohicky which increases the idle on cold starts (I don't mean
the fast idle!). Your best bet is to get your car warmed up to the point
the idle drops below 500rpm , and increase the idle. Of course, your
idle will be a little high on cold starts. The "book" says to adjust the
fast idle to 1000 rmp.(we need it here up north!). I don't know if this
should be set cold or when warm.
I'm having fun with my idle adjustment too. It doesn't help my Tach
just started acting up. I find the idle is *increasing* after the car
is run at highway speeds. I find I have to keep the idle up around 800
rpm (I have upgraded cam and pistins too. ) or she's pretty rough at
idle. (timed at 14deg static timing) That is supposedly expected with the
cam I have in.
Just my $0.000002 worth. I'm here to learn.
>
--
________ ___
/ ______/ | | Greg A.M.Johnson '72 & '66 MGB
/ \ ___ | | Biology Dept.
\ \_\ \ /\ __| | Dalhousie University
\______ / \________| Halifax, N.S., Canada
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