I've got a puzzle for you folks.
The car is my 1969 MGB. It has been enhanced with a hi-flow
supercharger sucking the air through an HIF 6 carburettor, and has
cage, belts and all the vents going to catch tanks required to make it
SCCA race legal.
About a week ago, I changed from the yellow carb spring to the stiffer
green spring, and have been experimenting with a couple of different
needle profiles. I have an O2 sensor hooked up to a nordskog m7009
meter, so I can keep an eye on what the mixture is doing at all
times. Very handy for dialing in the carburettor.
I've been having intermittent problems with the car leaning out and
not making any power at low loads. Especially if I've just been doing
some spirited (high engine load) driving. I've also, especially in the
last week, been having problems with the car leaning out at odd
times. Like when I'd be driving along the freeway at low to moderate
loads and I'd expect to see about 7 or 8 out of 10 leds lit, (a bit
richer than stoichiometric which is 5).
It would seem to run pretty well at full throttle. I'm also trying to
dial it in to get as much advance as I can on street gas, without it
pinging.
Yesterday morning, I had followed Dema Elgin's advice and had
tightened the valve lash on the intakes from .015" to .012", and that
seemed to help reduce the pinging. Though late last night when doing
some full power testing on the freeway, I still had a bit of
predetonation. It occured to me that the cold, dense, midnight air,
contributed to more "charge" in the cylinders.
I was heading home to Felton (in the Santa Cruz mountains) from
Mountain View at about 2:30 or 3:00 this morning. I had not been
strictly adhering to the 50 MPH posted speed limit on hwy 17 and had
been using a fair amount of the 130 hp available to me on the uphill
sections. A few miles before Scotts Valley (where the road flattens
back out) I had just noticed some headlights that looked like they
were trying to pace me, or possibly even catch up. Just as I had
backed off, lest it be a member of the constablery who did not
appreciate my spirited driving, my cell phone rang.
The call was from Becky. An attractive racer (even apart from the fact
that any lady who races gets bonus points in the attraction
department) that used to borrow my trailer to haul her car to the
track. I hadn't seen much of her for several months as she had moved
to Davis where she's attending college. I answered the phone, and she
asked what I was doing up at that hour. I asked where she was, Santa
Cruz or Davis. She said that she was in the truck next to me.
We decided to stop at the Denny's at the first Scotts Valley exit to
catch up on what we'd been up to for the past few months. Just as I
was pulling into the Denny's parking lot the car died. The same old
problem of not wanting to run at low loads after spirited driving.
A couple hours later (the water had cooled off to about 130F), it was
way too late in the morning and we went to leave. The MG fired right
up, ran for a couple seconds, then died. I tried many variations on
the theme, but the car would only run for, at best, a few seconds at a
time. At one point, when I revved the snot out of it, the car seemed
to run for longer so I tried, wiht no success, to just keep the power
up and drive home. I made it nearly 30 feet.Becky used to work at the
Chevron next door, which was open all night, so we went next door to
see if by any chance they had an inline fuel filter. Luck was with us,
one of the guys who used to work there as a mechanic was there, knew
where the fuel filters were and gave me one.
I took off the metal inline filter. I had neglected to turn off the
ignition after it had last died, so I ended up spewing gasoline all
over, and in the process confirming that my fuel pump seemed to be
working just fine. We put in the clear, new, filter, fired up the car
and it ran just fine. For at least 15-20 seconds. The engine died, but
it was cold. I buttoned everything up, and went to drive home, but the
car would only run a couple of seconds before dying.
Becky gave me a ride home (less than ten miles). This morning when I
woke up after several restful hours of sleep. I realized that I had
seen a problem very similar to this a couple years before, when I had
prepped the car for it's first race.
I'll send the answer in a separate email in case anyone wants to try
to figure it out.
--
I've found something worse than oldies station that play the music I used to
listen to. Oldies stations that play the "new" music I used to complain about.
lrc@red4est.com http://www.red4est.com/lrc
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