mgs
[Top] [All Lists]

Re: play in connecting rod

To: "simon hurley" <simonsensis@hotmail.com>, <mgs@autox.team.net>
Subject: Re: play in connecting rod
From: "Lawrie Alexander" <Lawrie@britcars.com>
Date: Fri, 26 May 2000 07:13:48 -0700
Simon,

There has to be a bit of side clearance between the rod big ends and the
journal flanges, so a trace of movement would be expected. (The rod is
allowed to move because the wrist pin moves sideways a tad in the piston, or
the bushed end of the rod moves on the pin, depending on the type you have).
However, if your rods move easily and sloppily side to side, you may be
looking at a problem.

The best way to tell if you have worn big end bearings is to remove the
bearing caps and look at the bearing shells. If there is copper showing,
they are badly worn. If they are still greyish in color, they might be worn
so you need to get some Plastigage from your local auto parts store. You
place a small strip of this between the bearing surfaces and the journal
(after cleaning off the oil residue), then re-torque the rod nuts. (BTW, you
shouldn't even be in there if you don't have an accurate torque wrench!).
Then remove the bearing caps again and the flattened Plastigage will tell
you if you have too much bearing clearance. If a lot of wear is present, try
and get a micrometer and measure whether the journals have become ovalled.
If they are more than a thousandth oval, it's crank out time and full engine
rebuild time, I'm afraid!

Note also that if the upper halves of the shells - the halves in the rods
themselves - are showing copper but the halves in the caps are still grey,
you are probably suffering a severe detonation or pinging problem. Replacing
shells will not fix that aspect of your engine's maladies!

Lawrie
British Sportscar Center
-----Original Message-----
From: simon hurley <simonsensis@hotmail.com>
To: mgs@autox.team.net <mgs@autox.team.net>
Cc: AFairbank@Higbee-Inc.com <AFairbank@Higbee-Inc.com>
Date: Friday, May 26, 2000 3:39 AM
Subject: play in connecting rod


>Tell me if this is Ok please?
>
>Took the bottom off 77 MGB engine.  There is a little bit of lateral
>movement where the connecting rod attaches to the crank shaft.  Should
there
>be any movement and if so do you know how much?
>There is no movement up and down in the line of the connecting rod.
>
>Hope this question make sense.
>
>Thanks for your help of which I will need a lot if I am to get this machine
>running this summer.
>
>Simon
>________________________________________________________________________
>


<Prev in Thread] Current Thread [Next in Thread>