Paul A. Tegler, Jr wrote:
>
> 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
> 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
If you fit K&N filters, they 'flow' a lot better, meaning the mixture
will get weaker the higher the RPM. I recently tuned a 1622cc engine,
and whilst it ran OK at idle, by 4,000rpm it would give fantastic
blow-backs on try to accelerate. There was no real power after 3,500
rpm, and the plugs were white on checking after to run. This indicates
a weak mixture. No6 needles cured it instantly.
Neil
|