Kelvin,
Thanks - that helps. Maybe the idle was set with the clutch disengaged -
that would explain a lot if it was just done with the car in neutral, then
we'd probably see this effect.
- Tab
At 09:51 AM 10/19/99 -0700, Dodd, Kelvin wrote:
>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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