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Another carb question

To: <spitfires@autox.team.net>
Subject: Another carb question
From: "Terry L. Thompson" <tlt@digex.net>
Date: Wed, 3 May 2000 11:17:56 -0400
It turns out that these HIF4's are still giving me a problem. And before I
brake down and spend the $75 (quoted price) for a carb adjustment, I'd like
to get some opinions to see what I can do to fix them.

With the car at operating temperature, I balanced (using a unisyn) and tuned
the carbs. When you lift on the damper pin, the idle tone rises for a second
then drops to the idle before I lifted the pin. And it does this on both
carbs. The car idles under 1000 RPMs when warm (I estimate between 800 and
900 rpms by the gauge).

And when driving the car at temperature, it seems to run fairly steady, but
occasionally I get a studder or a pop (small backfire?).

Also when the car is cold, giving it throttle seems to give a smooth
accelleration. But when the car is under load (I put it into gear and try to
drive), I get all kinds of shuddering and popping and backfires. This
continues all the way up to when the temperature needle is pointed straight
up (warm). Pulling the choke appears to help a little bit but mostly seems
to make the RPMs increase.

Anyone got a clue as to what it might be?

Terry L. Thompson
'76 Spit 1500 w/HIF4's (from a 72 MGB)
Maryland



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