Tab:
There is no designed provision for reduced idle speed with the
clutch pedal pushed down.
What you are experiencing is the extra drag caused by the throw-out
bearing and the crankshaft being pushed forward into the thrust washers.
Have someone push on the clutch pedal whilst you inspect the crankshaft
pulley. There should be no discernable in and out movement of the pulley.
It is possible that you have excessive thrust clearance in the engine,
though unlikely. This is more a problem found in Spit/Mid 1500 engines.
The late MGB engine will have a noticable drop in revs with the
clutch as a byproduct of the single carb, lower compression and heavier
loading. (smog pump, big alternator etc). All manual cars have some drop,
the late B is more noticable. To the point that the factory manual
specifies the idle is to be set with the clutch engaged, if I remember
correctly.
Check to make sure there is not a thrust problem. (again, this is
unlikely). Then set your idle speed so that the engine does not die with
the clutch engaged. While you are at it, check mixture and advance. It may
be that you are a bit out of tune which will make the problem much worse.
The carbon throw out bearing is not intended for any kind of
constant or abusive use. Leaving the clutch in gear at a light, or dumping
the clutch will cause premature failure. At a light the gearbox should be
in neutral, end of story.
There are some reported problems with the roller bearing. The
geometry of the throw out arm may not be suitable for a roller bearing that
requires concentric accuracy for longevity. In other words the roller wants
to be absolutely centered. The carbon bearing doesn't care. The MGB arm
was designed for the non-caring carbon bearing. Is it a big deal? I don't
know. Doug at British Automotive Supply in Novato thinks it is, he has a
write up somewhere on the web. I've got one of the roller bearings and I'll
probably put it in my commuter MGB just to see. But then, I've never had a
problem with a carbon bearing.
Commuting. The best thing to do is to leave very early and not get
stuck in stop and go traffic. Or how about telecommuting? Driving Lexus
leather lined toasters appears to also be in vogue.
Since I love to sleep in, my bosses think of telecommuting as
another way for workers not to, and I think leather lined toasters are for
sheep. I find myself in stop and go traffic every day. What I do is leave
the car in a suitable gear that allows me to creep along, or roar up to the
back bumper leaving deafened toaster drivers in my wake. 1st or second
works well. A B can get down to 5 mph or so in first without bucking, if it
is in tune. When the traffic comes to a complete stop. The clutch goes in.
The car is popped out of gear and the clutch out again. Once in a while the
clutch gets to stay in for a short while. That's what you pay for not
getting up earlier.
Sorry for the length. I'm trying to avoid doing a menial task that
will make everyones lives easier.
Kelvin.
> -----Original Message-----
> From: Tab Julius [mailto:tab@penworks.com]
> Sent: Tuesday, October 19, 1999 9:04 AM
> To: Charley & Peggy Robinson; mgs@autox.team.net
> Subject: Re: Roller throw out bearing
>
>
>
> Well, the guy I bought it from (a listmember) said that was
> the case, and
> after he told me that I paid close attention, and damned if
> the idle speed
> didn't drop (a lot, I thought) when the clutch was in, more so than in
> other cars.
>
> He said that it was an emissions thing to cut down on the output from
> engines idling in traffic with people riding the clutch while
> waiting to
> go. It's plausible enough to be true, though I've never
> heard of such a
> thing, but the fact remains that they do drop quite a bit
> when the clutch
> is in, so I can't say I disbelieve him.
>
> From my point of view, I now start it in neutral instead of
> with the clutch
> in (which is my usual safety technique, and a requirement on
> many cars,
> actually). This helps it start better, but it's still a problem when
> shifting in lesser weather when the car's not fully warmed up.
>
> On the other hand, Larry's saying it's physics and the way it
> is. Normally
> that's what I would have thought, except for the tale of the "idle
> reducer". I don't live out west, so I don't know what they
> put on their cars.
>
> Thanks
>
> - Tab
>
>
> At 10:38 AM 10/19/99 -0500, Charley & Peggy Robinson wrote:
> >Hi Tab,
> >
> > I've never heard of this feature but of cuss my hands-on
> experience is
> >with CBBs. How did you find out about this feature? If it
> was word of
> >mouth I'd be skeptical. If you found it in a manual, that's
> a different
> >story.
> >
> > Now, there is a feature called "Transmission Controlled
> Spark Advance"
> >in the later model Bs. Perhaps your slowing of the idle has
> something
> >to do with that - I. E., a malfunction.
> >
> > Charley Robinson
> > '69 B
> >
> >
> >
>
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