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3-Main Vibration

To: MG Listserver <mgs@autox.team.net>
Subject: 3-Main Vibration
From: Chris Attias <cattias@cats.ucsc.edu>
Date: Thu, 9 Sep 1999 08:36:19 -0700
I've only been driving my 3-main B for a year or so, but it seems to 
me--from memory, rather than direct comparison--that the early engine 
is a bit "rougher" and vibrates more above 3300 rpm or so than a 
5-main.  At least mine seems to.

I've read a number of period road tests which mention this to some 
extent-- that the new 5-main engine was smoother than the 3, 
especially at engine speeds above 4500 rpm.  Later articles about 
rebuilding 3-mains mention the importance of balancing components as 
part of the rebuild.

If what I notice has to do with some peculiarity of my engine, the 
question is--what's causing it?  Imbalance in parts is possible, I 
guess.  Vibration damper gone bad?  High speed ignition problem (I'm 
using Pertronix module)?  Cam wear?  Got any ideas?  Is high speed 
roughness a characteristic of 1600 MGA engines?

On the bright side, it adds to what the Brits call "rortiness". 
Period charm.  (I once bought a couple of used Brooklands article 
reprint books on Morgans.  The previous owner had gone through them 
with a highlighter and marked out all the references to "rorty". 
Can't get more British than that.
Chris Attias
'64 MGB
'84 Alfa Romeo GTV-6

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