Did you check the mixture AFTER installing the K&N filter and the Peco
exhaust?
If not, that is most likely the culprit.
Either one will affect the mixture required by the engine.
It sounds like the mixture is leaning out in the upper RPM range. As a
"quick and dirty" check, increase the mixture by 1/2 turn on each carb
and try it out. If the fade goes away or lessens, it's a pretty good bet
the mixture isn't right.
You also may find that the original needles no longer are correct and
will need to be changed to ones that are a bit richer at the end.
I ran into a similar problem on the Midget when I made similar changes.
I finally had to get a couple of needles that were slightly richer at the
end, but leaner at the lower end. (go figure!) Fortunatly, a local LBC
shop had a good supply of needles and was good enough to let me road test
several til I got the right combination.
Good luck
Rick Morrison
72 MGBGT
74 Midget
On Wed, 5 Aug 1998 01:26:07 -0400 "Paul A. Tegler, Jr"
<wizardz@amdyne.net> writes:
>I also seem to have a similar problem. After setting up the twin SUs
>on my
>73 BGT I seem to have power fade at higher RPMS under load. Color tune
>says
>I'm right on the money as far as mix goes. I changed the air filters
>to the
>K&N MG plate setup, the dist. has been rebuit, and evben after
>installing a
>new Peco free flow exhaust to repalce the slightly crimped orig
>exhaust, I
>still have this power fade problem. Could it be the Dwell? Carb needle
>selection?( SU tune up book says with K&N air filter I should change
>from
>the AUD550 (FX) to the No. 6 needle? Any ideas?
>-----Original Message-----
>From: Ivan Lawton <w3ike@yahoo.com>
>To: mgs@autox.team.net <mgs@autox.team.net>
>Date: Tuesday, August 04, 1998 4:56 PM
>Subject: Missing MGB, clews needed!
>
>
>>
>> I installed a slightly used very low time rebuilt 18V engine in
>>my 79 B last fall. The engine ran perfectly until March 1998 when I
>>decided to set it up for the Maryland emissions inspection. Well
>>after adding a can of Dry gas to the tank and adjusting the Zenith
>>carb to spec it started missing at 2200 RPM to 4200 RPM. The engine
>>will not rev over 4200 under load and has no POWER. No load, no miss
>>and redline is easily attainable. A compression check indicates in a
>>range of 138 to 146 lbs. I have changed the entire engine electrical
>>system, carburetor and fuel delivery systems with no improvement or
>>change. Oh, BTW the crank to cam timing is dead nuts on as I have
>>disassembled the front of the engine to check that. Also there are
>no
>>manifold or break booster vacuum leaks.
>>
>> My clew bucket is now empty so does anyone have any ideas?
>>
>> Thanks for your help,
>>
>> IKE Lawton Annapolis, MD.
>>
>>
>>
>>
>>
>>
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