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Re: [Mgs] [MG-MGB] Delta Cam Lash

To: MG List <mgs@autox.team.net>
Subject: Re: [Mgs] [MG-MGB] Delta Cam Lash
From: Max Heim <max_heim@sbcglobal.net>
Date: Tue, 26 May 2009 10:38:13 -0700
While I can understand that the "hot" condition is the actual running
condition, and therefore is the condition under which one might naturally
wish to set the tolerance, in practice it seems to me that the process is so
poorly controlled that it would be unlikely to produce consistent results.
That is, after running the engine whatever length of time, the temperature
of the valves is consistently "x", but after removing the rocker cover, and
fiddling with the first valve, the temperature of the remaining valves is
now "x-y"; and the next one is "x-y-z", and so on. Some people attempt to do
this with the engine running, but as the rocker cover is removed, this is
not the actual operating condition, either.

On the other hand, it is theoretically possible to calculate the rate of
expansion of the metal of the valves, rockers, and pushrods to a high degree
of accuracy, and to take that into account in setting a "cold" rocker
clearance standard (presumably this has been incorporated into the factory
specification for cold clearances). So my contention is that setting them
cold is equally accurate, in theory, and more likely to be consistent, in
practice (in those cases where the factory has provided this figure, of
course). 

--

Max Heim
'66 MGB GHN3L76149
If you're near Mountain View, CA,
it's the primer red one with chrome wires


on 5/26/09 8:04 AM, James F Juhas at james.f.juhas@snet.net wrote:

> All the MGA and MGB shop manuals I have say to adjust them hot, and only
> give one spec.  John Twist (University Motors) and Barney Gaylord (MGA
> Guru) say the same thing in person and in print.  And the plate that
> mounts on my MGA engine says specifically to adjust when hot.
> 
> Larry Daniels wrote:
>> Thanks, Paul.  That's what I was thinking, too, but it seems to me that I
>> saw specs on a cam recently where they wanted it adjusted warm.  I just
>> don't remember where I might have seen that.
>> 
>> Larry
>> 
>> 
>> 
>> ----- Original Message -----
>> From: "Paul Hunt" <paul.hunt1@blueyonder.co.uk>
>> To: <MG-MGB@yahoogroups.com>; "MG List" <mgs@autox.team.net>
>> Sent: Monday, May 25, 2009 10:03 AM
>> Subject: Re: [Mgs] [MG-MGB] Delta Cam Lash
>> 
>> 
>> As standard clearance is .014 to .016 cold, and the majority of clearance
>> change will be down to expansion of the push-rods, I'd be doing the same
>> short
>> of any other documented value.
>> 
>> PaulH.
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