----------
From: Merryweather, George
Sent: Thursday, January 09, 1997 2:44 PM
To: 'Jeremy DuBois'
Subject: RE: MGB spigot bushing size question, bearings, and ?
MG vs Triumph?
Moss vs VB?
Moss, both US and Europe, and usually Europe has better technical =
answers, says the 1-1/2 is the later one, but I still think, that in =
this case, bigger is better. The bushing is designed to carry a load, =
(or maybe to prevent an unequal one), and if you change loads when you =
change gears, which you do, (should you ever forget to put in the =
bushing, you get a real ugly rattle on up and down shifting), then you =
would be changing loads more often with a full synchro, rather than the =
3 synchro, so the longer bush would help compensate for the more =
frequent shifting, which would allow the bush to wear out less speedily. =
Wow! That made sense coming out of the keyboard, but I'm not sure =
about what it will be like reading it, so I won't.
OOOOHHHHH! A brand new Tan over white XJ8 just pulled in the parking =
lot, driven by a very attractive blonde lady. I hope she won't be =
offended if I go look at her car and ignore her. Nice Car!
So to wrap this up quickly, bearings...I will oversimplify this greatly, =
so as not to exceed my limited expertise. How's that for a disclaimer!
There are basically two types of bearings. For this application, =
anyhow. Steel backed with a hard alloy on the front, or steel with 2 =
layers on the front, commonly called, tri-metal. I think that Vandervel =
calls it VP2 (?). The first mentioned bearing is hard, and you can not =
scratch it with a fingernail. These are used for higher load engines, =
i.e. racecars or maybe Barney's. The second has a very soft top layer. =
(Now back to some basic engine theory....if the engine has been =
assembled properly, and the right oil is flowing to the right places, =
and there is no unusual stress on the engine, then the oil acts as a =
lubricant between the bearing and the crank, and there is no actual =
metal to metal contact. Add stress, bad shifts, high rpm, heat, dirty =
oil, etc., and you will either contaminate the lubricant and/or cause =
metal to metal contact) (Top fuel dragsters can actually measure the =
side to side expansion of a bearing after a run. Using a technical =
term, it gets 'squished') OK, so hard bearings are OK, but the added =
feature of the softer ones I believe is called 'embeddability'. Sorry =
for my spelling. What this does is allow minutes contaminants to get =
embedded in to the surface of the bearing, rather than actually wearing =
against the entire surface. Once it is embedded, it is covered with =
oil, and away from the surface of the crank. A harder bearing allows =
the contaminant to run its course over the surface of the crank/bearing. =
A soft bearing is fine for most LBC applications. Let's exclude Barney =
and his 9,000 rpm MGA (Keep smiling, B!). A lot a shops, and owners, =
prefer the softer, tri-metal bearing.
So your problem....you scratched a soft bearing. Take a CLEAN red shop =
rag. CLEAN, no dirt, or metal shavings from the previous shop if you =
get your rags from a service, CLEAN, a new one is good, and carefully =
buff the bearing with it. The red rags are typically coarse in texture =
so provide a soft abrasive effect. You may have gone too deep with your =
nail to buff it out, but give it a try. If the bearing begins to =
discolor, or is it 'discolour', then you have gone too far, and it's =
time to get a new one. Some may say, leave it allow, I say replace it. =
But try the red rag approach first, it's a lot cheaper.
Sorry for the long reply but the Jag left too quickly!
George Merryweather
merryweather@connectware.com
----------
From: Jeremy DuBois[SMTP:jer@thlogic.com]
Sent: Thursday, January 09, 1997 7:35 AM
To: merryweather@venus.connectware.com
Cc: MG's
Subject: Re: MGB spigot bushing size question
>=20
> A rather nebulous response, but it is the best I can do.
>=20
> The 1 and 1-1/2 are theoretically interchangeable, BUT...
>=20
> The 1" was used consistently until the start of the all synchro =3D
> transmission. At that time, and for about a year, it was decided that =
=3D
> the 1-1/2 provided more support, and that with the new transmission, =
=3D
> that support was needed. The transition was then made to the 1-1/2. =
It =3D
> was not done at the introduction of the new tranny, but in the 1969 =
=3D
> timeframe.
>=20
> The various 'experts' I have spoken with say basically the same =
thing. =3D
> Replace it with what came out. Obviously that won't work here, so the =
=3D
> next answer is 'more is better', put in the 1-1/2. I know one shop =
that =3D
> refuses to put in the longer one, saying it doesn't make a difference, =
=3D
> but if that was the case, why did they make it?
>=20
> I would go with the longer one. (FWIW, Moss sells 3 of the long ones =
to =3D
> each 1 of the sort ones).
>=20
> In this case, I agree that more is better.
>=20
Thanks much for the help George (and to everybody else who mailed me
privately) Only question I have now is that the VB catalog pretty much
agrees with the above info except they've got it the other way round =
(the
1-1/2" used on the non-syncro box, and the 1" on the all-syncro). But
you're not the only one who has suggested it's the other way. Perhaps =
VB
just got it wrong?
Hopefully I'll soon have this engine all back together, though its =
tough
to work on in the winter cold, and with the Tr*umphs fighting for my
attention. Another question you, or any of the other bright MGers here,
might be able to answer for me. I noticed, by accident of course, that
fingernails can put very shallow, but discoloring, scratches in the new
conrod bearing shells. Time to get another set of bearing shells and be
more careful, or not significant enough to worry about?
----
Jeremy DuBois jer@thlogic.com
Manager, Info Systems http://www.thlogic.com/~jer/
Thermalogic Corporation '60 TR3A, '74 MGB, '76 Spit
|