Hi gang,
I've been having fun with the MGA lately, now that it has the new cam and
is running like an MG again. So far this season two autocross dates, one
index trophy with 41 drivers and one 1st in class, a perfect score. Also
three TSD rallies, one 3rd place (bogus route instructions) and two 1st
overall trophies.
Saturday I was on the expressway for the first time with the new cam,
cruising with several other MGs on the way to autocross driving school
where I was honored to be one of the instructors (again). Well, some of
the other MGs wanted to play on the interstate, so I pushed the 1500 engine
up to 5500 rpm and set the cruise control (about 93 mph). Funny thing was
that it didn't mind purring along like that with only about 2/3 throttle,
where it used to be about topped out with the stock cam. When I pushed it
to 6000 rpm (about 102 mph) it got a little raspy and the torque
disappeared (valve float). Well, the new cam gives considerably more lift
at the valves, so there is induced considerably more inertia into the valve
train, so valve float now occurs at a lower engine speed. Next up on the
order list, a new set of competition valve springs.
About the time I was figuring out where valve float would happen the MGB in
the rear view mirror suddenly pulled off onto the shoulder and stopped, so
my MGA did a sudden pullover and backed up to see what was amiss. His
power had suddenly dropped, and the oil pressure went down near zero. The
dip stick showed full, but the stuff in the crankcase was obviously mostly
gasoline. The result was one failed rod bearing on #2 cylinder, retiring
that car for the day. We collectively drained the crap out of the engine
and installed fresh oil, using what was on hand amongst the few cars that
had stopped to assist, some 20W50 dino oil and some 10W50 synthetic. Then
pulled off #2 plug wire, removed #2 spark plug from engine into owner's
pocket, and sent the car home at a casual pace, presumably without further
incident for the day (BTDT, more than once). One other detail, that MGB
was sporting twin HIF carbs.
Now I have question, just out of curiosity. Is it common for the HIF carbs
to overflow the internal float chamber and flood the engine with raw fuel
going down the intake throat? I think we were talking about at least 2 to
3 quarts of fuel in the crankcase within 1000 miles of running since the
last oil change. Having seen this phenomenon occur once now, I'm happy
that my car uses H4 carbs and not HIFs. Mine would just burp the errant
fuel out the overflow pipe onto the ground (or onto the exhaust manifold if
the overflow pipe is broken or missing).
Barney Gaylord
1958 MGA with an attitude
http://www.ntsource.com/~barneymg
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