At 12:59 PM 4/13/2000 -0400, Gordon Bird wrote:
>Had the A out last night, after normal valve/points adjust, etc,etc. Fine
until warmed up (@190F), then at @ 5000 rpm's I get a miss and loss of
power. Pulls just fine up to that point. When cold, pulls strong up to
red line, when I quit. I know Barney, it should be able to go higher. ;^)
Any clues?
Turn the carburetor mixture two or three flats (1/3 to 1/2 turn) richer,
and give it another try at top end (might idle rough). If it runs better
at speed that way you may need richer needles. Check the numbers on the
side at the top end of the needles (have to remove to see) to verify that
your car still has the original needles. When I bought my car it did the
same thing, ran great up to about 5000 and then sputtered at higher engine
speed. Turned out to be the wrong needles in the carbs.
If a richer mixture doesn't fix it, start checking around the distributor
contact points for high resistance grounding or a bad condenser. Use an
ohmmeter with a milliohm scale to check resistance through the distributor.
From the terminal on the side of the dizzy to the engine block you should
get no more than 1/4 ohm with the points closed (250 milliohms max). If
you find higher resistance there it needs to be fixed. Maybe the points
are burned. Maybe the body of the dizzy doesn't have a good clean contact
with the engine block. And there is that generally invisible wire under
the moveable contact breaker plate to ground the moving plate to the body
of the dizzy. This is supposed to be a finely stranded and very flexible
wire, but with extended use and age it can still break (usually near one
end). A broken wire here can give an intermitent contact that checks out
fine at rest but fails when the vacuum advance kicks in and rotates the
breaker plate.
Let us know what you find,
Barney Gaylord
1958 MGA with an attitude
http://www.ntsource.com/~barneymg
|