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Plug gaps, Frozen parts, Handling, endless projectc.

To: mgs@Autox.Team.Net
Subject: Plug gaps, Frozen parts, Handling, endless projectc.
From: Bill Eastman <william.eastman@medtronic.com>
Date: Tue, 29 Apr 1997 14:53:40 -0500
Sure, take a couple days off and all heck breaks loose!  I am on the digest
now so don't confuse my late replies with lack of interest.  

Concerning wider spark plug gap and peformance:

I will preface this with a disclaimer.  I took IC engine classes almost 20
years ago now and I refuse to open the books again.  Hopefully my memory
has aged better than my eyesight.   The burn cycle in a cylinder has two
distinct phases during the normal combustion cycle.  The first stage is
ignition.  Mixture ignition is a statistical process.  There is a delay
between the spark and establishing a flamefront.  This delay depends on how
much / what type of fuel air mixture is directly exposed to the spark.  I
believe that rich mixtures have more delay, for instance.  Widening the gap
increases the chance that the spark will contact the "good" areas of the
fuel air mixture and produce a more consistent ignition delay.  More
consistent delay means that more individual combusion cycles are closer to
optimum and this means more power.  For the record, the second phase has
something to do with propogation.  A third, undesirable phase is detonation
which should be avoided if possible.  So, provided sufficient voltage is
available, a wider gap will increase performance and, to a lesser extent,
engine smoothness.

For the person with the frozen suspension pivot:
When I ran into this, I replaced the offending pieces.  They are fairly
cheap (less than 40 bucks total per side).  In both cases where I found a
rusted pivot, I also found a loose pivot bolt and oblong A-arm holes.  I
prefer round holes in my suspension components.  Oblong holes / a worn
pivot bolt could also explain some extra negative camber.  Also, too much
heat can weaken metal parts and, in my opinion, MG lower A-arms are _not_
overdesigned.  Don't forget the thrust washers / seals/ seal supports/ etc.
when buying the new parts.  These will be stuck on the frozen part, too.

Concerning handling questions:
Everything that I have read / heard / experienced points to the rears
springs on MG's being too stiff, not too soft.  Because of this, I would
question whether changing to GT springs would benifit handling.  I will
admit that most of what I have heard relates to the MGA but the MGB is very
similar so I would guess that It would apply.  If you believe this, the
best street handling approach may be to remove one leaf from each rear
spring and add a small rear Anti-roll bar to get back the roll stiffness. 
This would probably lower the car a little so something would have to be
done with ride height.  I also understand that the main advantage of tube
shocks over lever shocks is in their ability to reduce resistance to sharp
movements.  This helps keep the wheels on the ground and also improve ride
considerably.  I would expect that the effect on absolute grip except on
rough roads would be negligible.

And on endless projects:
One of the reasons that I bought my particular MGA was that the work it
needed wast the stuff I enjoy (mechanical, puttsy stuff) and the work that
was done was the stuff I wouldn't or couldn't do (body work).  I knew when
I bought the car that I would be constantly fixing / impoving it.  That was
one of the attractions.  Every day I find something else that has to be
added to the to-do list.  I noticed the other day that the windscreen
rattles over bumps.  I looked closely at the situation and found several
things that need improvement.  The windscreen uprights are spread too far
apart so I should remove some packing sometime.   One screw holding the
frame to the uprights is broken off and another is stripped.  If I remember
correctly, these screws are not UNF but British Motorcycle Standard (26
pitch).  On closer examination, I also noticed that the erstwhile restorer
had chosen, for simplicity's sake, to assemble the windscreen without any
rubber or other packing between the frame and glass.  I am sure this made
for and easier installation and it sure looks clean but it does allow the
glass to rattle in the frame.

Anyway, the windscreen has been added to the list.  It isn't a reliability
issue so I probably won't get to it for a while.  When I do, you can bet
that I'll be asking the list for advice.

Regards,
Bill Eastman
61 MGA- a project a minute

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