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Re: Some People on the list

To: "Mike Razor" <>, <>
Subject: Re: Some People on the list
From: "Paul Hunt" <>
Date: Thu, 28 Dec 2006 14:34:05 -0000
Dunno about an MGA (although it is unlikely to be different) but on the B 
hardened inserts are used for the seats as well as special valves, 
originally the seats were part of the main head casting (but you probably 
already know that :o).

On the one hand I'd just replace the one valve and lap it in.  But on the 
other a significant amount of protection against valve seat recession from 
use of unleaded comes from the years and 10s of thousands of miles of use of 
leaded fuel beforehand, leaching into the seats and valves.  By just 
replacing a valve the seat will still be protected unless it is *recut*, but 
the valve won't be.  But then the problem of using unleaded has always been 
described as valve *seat* recession in my experience, i.e bits of material 
being transferred from seat to valve from micro-welding, and then probably 
burnt off the valve.  In which case a new valve may well still be OK.  There 
is also the usage to consider - whereas long journeys at motorway speeds of 
70 or so are likely to cause a problem on an unprotected engine, lower speed 
touring much less so.  There are also additives to protect against VSR, I 
use Castrol's in my roadster (the V8 was built with hardened seats anyway 
being alloy headed).

All-in-all I think I'd just replace the single valve, see how it went, and 
if it had problems of recession only then convert the head and valves to 
unleaded.  The less unnecessary work you do the less the chance of a 
knock-on problem.


----- Original Message ----- 
> On an MG note I am about to have the head pulled off my MGA due to a bad
> valve.  I wonder if I should just replace all of them and if so what is 
> the
> best choice for seats and valves?  I understand there are seats and valves
> that are produced to accept unleaded gas.

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