Misfire at cruise, that changes to smoothness and some accelleration with
choke, indicates a weak needle. Cruise at various rpms and decide which
is/are worst. Then in your workshop put a measuring stick down the dashpot
to see how high it rises at those rpms. You should be able to translate
that to one or more positions on the needle, and possibly an indication of
severity at each. Then download the needle selection program from
http://ro.com/~rmason/mgpage.htm/#helpzone to help you choose a better
needle.
PaulH.
-----Original Message-----
From: Paul Tegler <wizardz@amdyne.net>
To: MG LIST <mgs@autox.team.net>; MG list <mgs@autox.team.net>
Date: 20 January 1999 05:01
Subject: stammer at speed - done it all!
>OB's a bat-out-of-hell accelerating
>but stammers at cruise
>
>Since I first posted this problem...
>the engine has been swapped (and O/D trans)
>new STOCK fuel pump installed
>new AUD405 carbs with AAA needles red springs K&N filters
>rebuilt dist (multiple times)
>pressure tested the manifold (off the engine) no leaks
>installed a vacuum gauge to monitor the situation
>new vac adv unit.
>Gunson's color tune and Gastester have both been used
>to tune
>
>To make sure crankcase pressure wasn't causing fuel starvation
>Tonight I disconnected the tappet cover vent pipe from the carbs
>and plugged the carb ports
>disconnected the float vents from the carbon canister
>completely re-routed all vac lines and fuel lines in the engine bay.
>checked the floats again in the NEW carbs
>
>IT STILL stammers -- pull out the choke at speed and you
>can feel the power pick up and smooth out
>WHAT's UP? This is getting ridiculous - but I'm the type
>that just won't give up
>
>Could this problem still be related to the velocity of the air entering
>the carbs with the minimal limiting of the K&Ns
>What if I added velocity stacks inside the K&N's
>(would have to press fit them into the orig base plates)
>PLEASE PLEASE PLEASE SOMEBODY ASK SOMEONE
>NOT ON THE LIST ABOUT THIS!
>I'LL PAY FOR THE INFO WHOEVER COME UP WITH A SOLUTION!
>
>TIA
>
>Paul Tegler
>OB - 1973 MGBGT (Blaze Red, (orange))
>YB - 1973 MGBGT (Primrose Yellow)
>Millersville, MD (South of Baltimore, North of Annapolis)
>wizardz@amdyne.net
>http://www.amdyne.net/~ptegler/mgmain.htm
>
>
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