Re: alfa-digest V8 #220 - Define Blueprinting

[AlfaNeely@domain.elided]

In a message dated 11/12/2001 9:44:24 AM Central Standard Time, 
owner-alfa-digest@domain.elided writes:


> 
> Date: Sun, 11 Nov 2001 22:10:51 -0500
> From: maxid@domain.elided
> Subject: Define Blueprinting
> 
> Would anyone please define what it means when an engine is "blueprinted"?
> Thanks,
> Sonny
> 
> 

       Blueprinting means making sure everything inside the engine matches 
the factory specifications or "blueprints."  There are tolerances on any 
manufactured part.  If all parts are within tolerance, they are "blueprinted."
       All pistons should be exactly the same, with the distance from piston 
pin to piston top being the same and the diameter of the pistons will all be 
the same as will the bore of the liners.  The connecting rods should all be 
the correct length.  The throws on the crankshaft should all be ground 
exactly 180 degrees apart and the stroke will be exactly correct.
       If all those parts are the same, then every piston should come to 
exactly the same place in its bore at TDC.  You might have to "deck" the 
block to make that happen.  Then if you match every combustion chamber to 
tolerance, then every cylinder will have exactly the same compression ratio.

       Blueprinting an engine really means everything is within tolerance.  
However in normal use, if you machine every part to make it perfect, you are 
going a step beyond simple blueprinting.  You are bringing everything to 
closer than factory tolerances.  You might make sure all parts fall exactly 
in the center of the factory tolerances.  Or you might want all pistons to be 
exactly at the outside limit of the tolerances.  You might do the latter to 
maximize cubic inches of the engine while still being within factory 
tolerances.
       Balancing an engine is similar, except you are making sure everything 
weighs what it should.  Or at least you make sure everything weighs the same. 
 Balancing and blueprinting are generally done together.

       By the way, I read the results of a protest in Sports Car Magazine a 
while ago.  Seems a Camero or Firebird in an SCCA class that required a 
"stock" engine was torn down after the SCCA National Run Offs a year or two 
ago.  Everything was "within" the specified tolerances - that is to the 
maximum of every tolerance.  The resultant engine came up with too high a 
compression ratio.  The entrant / protester argued that the factory specified 
compression ratio was incorrect when everything was brought to "tolerance."  
He lost.  The appeals court found that everything was TOO correct and the 
result pushed the compression out of the allowed range.
       This is from memory.  I am sure I have not related the results of the 
protest as accurately as it was originally written.


Ciao,
Russ Neely
Oklahoma City

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