Bob,
If the trips are fairly short (under 30 miles) I keep her below 4500 which
is around 75 (4.3 rear end, 165-15 radials). On longer trips I sustain
4100 which is a nice sweet spot in the rev range (stock except for NWI mild
road cam) and about 70 mph. I don't keep up with traffic on freeways at
that speed but I do get from point A to point B in a reasonable time. In
my opinion, the key is good oil (I use Mobil 1) in an engine that isn't
worn out. B series engines use up their rod bearings in about 75k miles
the first time and more often after so replace them if it is time. A less
optimistic person may set a 4000 rpm sustained limit which is about 68 mph.
True pessimists with old rod bearings may set a 3500 sustained limit which
is about 60. A 55 mph limit, to me, would make driving the A more
frustration than it is worth.
On a side note, I put new exhaust valves in last year without hardened
seats. As long as I take it easy, I am OK but at higher speed the valves
can close up in a hurry. If I run 75 miles at 75 (OK I push my limits
occasionally) I have to adjust the valves. I will probably have hardened
exhaust seat fitted this fall or sooner if do a lot of longer trips.
How about some other input? What do you do, Barney? Lawrie, how often
does a B series MG engine show up with a thrown rod or a dropped valve?
Personally, I think that highway running is about the easiest thing we do
to these cars. As always, My opinion, YMMV, see participating stores for
details, you need not enter to win, yada yada yada.
Regards,
Bill Eastman
61 MGA who likes to be given a little reign and would much rather blow up
at 75 than be forced to run at 55.
>>> Bob Howard <mgbob@juno.com> 03/02/99 08:03am >>>
Bill,
70 MPH cruise in your MGA--what RPM is that and what rear-axle gears
are you using? One of our A-owning club members just won't run his car
more than 55, which is slower than I cruise my MGA 4.1 geared TD. Perhaps
your information will give him some peace of mind at "normal" road
speeds.
Bob>
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