[Supras] Weired piston height

[tom]

Bernie,
I had the opposite problem with my JDM.  The top #1 piston actually rose above the block by nearly a 64th of an inch.  When I got the motor it had ruptured the head gasket in the first, fifth, and sixth cylinders, all on the exhaust side.  I believe that the gasket that I removed was just slapped on the engine as part of a sloppy repair for a previous problem, likely in Japan, for the original owner.  

If you look on the oil pan gasket surface of the block there will be a series of six numbers, each indicating the correct piston size, corresponding to each of the cylinders, front to back.  My block was 2, 1,1,1,1,1.  I think that part of the previous repair included replacing the  first piston (a '2') with another, though wrong, piston.  When placing the head on the block I noticed that the valves rested on the piston crown and held the head off the block.

I just put in a used '1' piston that I got from another member and it has worked well enough for a year, as I rebuild another JDM to take its place.  It blows oil smoke when decelerating- suggesting that the rings don't seal.  

That was a trashy motor, from Noyan (http://www.noyanusa.com/), that had supposedly been "cleaned, carefully inspected, and pressure tested."  Caveat emptor. 

Tom 87NA-T

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Message: 1
Date: Sat, 07 Jul 2007 17:14:21 -0400
From: "berniek at technicaldevelop.com" <berniek at technicaldevelop.com>
Subject: [Supras] HELP:  Weired piston height
To: "Supras at supras.com" <Supras at supras.com>
Message-ID: <4690022D.2000301 at technicaldevelop.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Man, if I ever needed help from knowledgeable people in this good group, 
now is the time.

I got the head off my newly bought '91 turbo to lap the deck and install 
a Cometic gasket and rebuilt head.  While cleaning the piston crowns, I 
noticed that the first cylinder piston crown is about .100" lower than 
the others.  Measuring it and piston 6 to the deck, the .100" additional 
depth is always there!.  There is no vertical slop indicating bad 
bearings or a bad wrist pin.  That was tested by turning the engine over 
to pull #1 piston down in the bore, and then tapping down on its crown.

All of the bores are just about at the factory initial size (3.270" 
measured with an inside micrometer.  #1 piston crown looks fine.  All 
are stock turbo pistons.  There are some very light scratches at the 
backside of the bore but no top ridge in any of the cylinders. 

This is the weirdest thing I've ever seen.  Is there any chance that it 
was assembled with a piston or rod from a different year?  The engine 
ran fine before disassembly.  Any and all suggestions would be very much 
appreciated. 

       BernieK