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Discussion Starter · #1 ·
Knowing that there's just

Knowing that there's just a few 12-cylinder and other hi-performance folks that frequent this forum...here's some "eye-candy"...

Stock 8.8:1 BB piston versus JE 11.0:1 piston. Notice the stock 4-ring design versus the contemporary JE design.



 
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Discussion Starter · #2 ·
David: If you don't mind

David: If you don't mind me asking....what was wrong with your engine that necessitated the rebuild?

Did you have to modify the heads for valve clearance?
 
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Discussion Starter · #3 ·
Henry,

It's a long, lon


Henry,

It's a long, long story about why I rebuilt the engine...I'll get into it later...

As to the pistons...
No, no head modifications were made. As the compression jump was pretty substantial, many precise measurements were required, before having the pistons made.

-Combustion chamber volume
-Head gasket thinkness
-Valve diameter and actual lift
-A piston was sent to JE for vavle cut out positions

Once the pistons were made, I fitted one in the block...and covered the valve cut- and the top f the piston with modeling clay. The cylinder head was installed, torqued....and the cams installed and timed. After the engine was rotated several times, to verify no initial interference...the engine was set back to TDC, and the head was removed. The indentations from the vavles were measured in the clay...According to JE, as long as I had at least .080" clearance on the exhaust vavle, no additional piston machining was necessary. As I had .090" clearance...she was good to go. Piston to head clearance was measured as well...about .110".

In the event there was not enough exhaust valve to piston clearance, the pistons would need the valve pockets cut a bit deeper...Not a big deal for a competent machine shop.

A lot of work...but there's a noticeable improvement in torque now, particulary as the engine is breaking it (hit 1100km today).

Regards,
David
 
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Discussion Starter · #4 ·
>>the pistons were mad

>>the pistons were made, I fitted one in the block...and covered the valve cut- and the top f the piston with modeling clay.<<

I'll dig up some pics I have of the modelling clay procedure and post them .

Regards, JRV
 
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Discussion Starter · #5 ·
>>I'll dig up some

>>I'll dig up some pics I have of the modelling clay procedure and post them . <<

Took awhile to get the time but here are pics of modeling clay being used to gather piston to valve clearance data:




 
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