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"Misfire" at speed

To: british-cars@autox.team.net
Subject: "Misfire" at speed
From: "John M. Trindle" <jtrindle@tsquare.com>
Date: Thu, 6 Oct 1994 08:24:40 +0000
Will, I had the same problem with my single HIF6 (I know I keep switching 
the number back and forth, but we compared it with a known quantity and 
it >is< a 6 on an Austin Marina manifold).

Anyway, my float sunk.  This caused fuel to spew right through the carbs, 
out through the vent hose and through the charcoal canister.  I (of 
course) brilliantly deduced this was a sunk float after pouring several 
gallons of gas all over my feet.

When I put the carb back together, I got a very harsh sounding motor but 
drove it all the way to work without incident.  When I got off work, I 
drove it down the road to my friend's... but only made it a couple 
blocks.  I could sit with the ignition switch >on< for a minute and then 
start and drive for a minute.  The faster I went the shorter that minute 
was. 
 
Naturally, the float was closing the valve too soon.  I adjusted it 
the next day and drove 50 miles to an autocross school.   The car would 
cruise at 70 (indicated) no problem.  At 75 it would go for about 20 
seconds and then "misfire"... no gas!  Also in 3rd gear at WOT it would 
die at about 50 mph (great for merging onto the interstate).

After adjusting it again >just a smidge<, it ran great.  Naturally, I 
then decided to take off the HIF6 and Austin Marina manifold and put on 
the twin HIF4s and the MG manifolds.  The car hasn't worked since <sigh>.

Your business of sitting at the stop light and then having it work better 
for a while sounds like a low float bowl level, or restricted valve.  
Remember that a lower float bowl level will act to lean the mixture slightly.

John M. Trindle     | jtrindle@tsquare.com | Tidewater Sports Car Club
'73 MGB E Stock     | '69 Spitfire E Stock | '88 RX-7 C Stock



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