Something is wrong with what you said. Your MG should be geared to run 17.9
mph per 1000 rpm in 4th and 22.3 mph per 1000 rpm in 4th overdrive. This
means at 3500 rpm you should be cruising at 63 mph in 4th and 78 mph in 4th
OD. Your car should cruise at 4000 to 4500 rpm all day with no strain on
the engine in 4th, might be a bit much in 4th OD as 4500 equates to about
100 mph in 4th OD.
I think what you are perceiving as strain at 3000 rpm is really just the
music the engine makes when it is getting into the power curve which is
around 3000 to 4500 rpm.
When my 72 w/o OD was new, I had a friend who also had a new 72 with OD and
my car would run out of power at about 105 and his something over 110, so
rpms was not the limiting factor but the car just ran out of horsepower to
pull the cars faster than those speeds.
Dave 72 B
----- Original Message -----
From: "Plant, Keith Contractor (NSAGAETA 60)" <PlantK@nsa.naples.navy.mil>
Sent: Thursday, June 14, 2001 2:59 AM
I'm usually a silent list reader, but let me throw my hat into the ring. I
purchased my first MGB ('69) in November of last year. Tach'o yellows at
5500 and reds at 6000 rpm. The car has overdrive. My question is this...
When I'm driving, I usually change gears at about 3000, maybe 3500 rpm as
this is when it sounds as if it's beginning to strain the engine. In my '97
Mitsubishi Mirage, it's about the same, maybe 4000 tops. The problem is
that by the time I'm in 4th gear at 3500 rpm, I'm only cruising at about
40-50 miles an hour. If get the rpm up to 4500, the engine sounds like it's
really straining and I only just break 55-if I'm lucky with tail winds, 60.
This happened both before and after I had the engine converted from leaded
to unleaded and rebuilt.
'69 B enjoying Coastal Italy
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