Message-ID: <32264C12.68BF@flash.net>
Date: Thu, 29 Aug 1996 19:04:02 -0700
From: David Littlefield <dmeadow@flash.net>
Reply-To: dmeadow@flash.net
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To: "W. R. Gibbons" <gibbons@northpole.med.uvm.edu>
Subject: Re: Rebuilding an MGA 1500
References: <Pine.SUN.3.91.960828151801.1207C-100000@northpole.med.uvm.edu>
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W. R. Gibbons wrote:
>
> On Thu, 22 Aug 1996, David Littlefield wrote:
>
> > "Bluprinting" is one of those terms that uninformed people (like me)
> > throw out trying to impress other uninformed people with their great
>
> <clip>
>
> > place in the engine where one moving part touches another. In
> > blueprinting, all or most of these clearances are reduced to the closest
> > factory spec. Whereas when the car was built the factory would allow a
> > relatively wide tolerance, which means that any particular engine could
> > have clearances at either end of a fairly wide range.
>
> > I hope I'm not all wet with this, since its been seven or so years since
> > I redid my engine. If I am I hope the list subscribers will be kind in
> > correcting me, although I might deserve some ribbing for using the term
> > in the first place.;)
>
> Probably someone has said something by now; I just got back from vacation
> and I'm going through a big backlog. My understanding of blueprinting has
> been different from what you describe. Basically, I've understood it to
> mean that one builds the engine within factory tolerances (so as to stay
> within racing rules that require stock engines), but to use those
> tolerances in the factory range that provide the best performance.
> Generally, this would mean using tolerances at the large end of the
> factory range, not reducing them to the minimum factory spec.
>
> Ray Gibbons Dept. of Molecular Physiology & Biophysics
> Univ. of Vermont College of Medicine, Burlington, VT
> gibbons@northpole.med.uvm.edu (802) 656-8910
Okay, now here's the final solution and hopefully the definitive answer
(as much as one can be given) to the question "what is blueprinting".
While in my favorite bookstore today, purchasing a copy of the new book
"MG Sports Cars" by John Hellig, I found a book called "The Step by Step
Guide to Engine Blueprinting". I read the introduction, which included
the author's two-page definition. Since I didn't want to buy the book
and to take up bandwidth with all of that, I'll try to summarize what I
learned.
Largely, the author confirmed my earlier posting and definition,
including the aspect that different people give the word different
meaning. So be careful when talking with your machinist as to what work
is going to be performed. However, my earlier post was incorrect that
the minimum factory spec is necessarily sought, as Mr. Gibbons states
above. Mr. Gibbons is correct that the OPTIMAL clearance is used for
the parts concerned, but that optimal clearance could be anywhere within
the factory tolerance range. (It doesn't make sense to me that that
would necessarily be at the large end of the range, particularly since
any wear at all would quickly result in exceeding factory tolerances and
a generally "sloppy" engine). The optimal clearance is determined by
the machinist for the particular engine being built. Since I was on my
lunch hour, that's about as far as I got in the book, so I don't know
how the machinist establishes the optimal clearance, but the impression
I got is that would be dependent upon the use to which the engine is
being put and the various modifications to stock that might be made.
For some engines, I suppose, there would be a wealth of literature to
that effect.
Hope this clarifies.
David Littlefield
Houston, TX
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