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"Gin'iro Ryuujin"
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In another thread questions were asked about the 5.7L pistons and pistons on the 6.4L Here is an excellent wiki article on the type of piston used in the 6.4L: http://en.wikipedia.org/wiki/Hypereutectic_piston

The 6.4L pistons add silicon to the aluminum cast. This makes the piston slightly lighter, more durable and having greater heat resistant i.e. doesn't expand as much as aluminum cast pistons. The heat resistance allows for tighter tolerances between the piston and cylinder walls which was important for cold starts e.g. kept unburnt fuel from escaping into the exhaust in the 1980s. The normal range of silicon to aluminum is 16-19% and under normal operating conditions the hypereutectic piston is superior to the cast aluminum piston.

From what I read these pistons are stronger e.g., harder than normal cast aluminum pistons and there in lies the problem when adding FI. Being harder means they are also less flexible, i.e. brittle, meaning they don't deform as much under pressure and boost increases pressure in the cylinder. The piston have been known to blow under high boost levels or problems with detonation. According to the article the hypereutetic pistons need to have the silicon content reduced to 11% to withstand minor detonation.

If I were a 6.4L owner I would forge the pistons when adding boost. Hope the article helps.
 

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Premium Member
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9,143 Posts
I agree with this but just has important is where the top ring land is...or to put it another way...how very little metal is between the top ring grove and the piston top. This is the part that I keep reading about people having bits breaking off even on relatively low boost with good proven tunes. Same boost levals and tunes where not having this problem on the 6.1's or 5.7's.
 

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Now that was dumb!
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6,029 Posts
Al LOL sorry I dint see your post. I made a post concerning pistons and differing types for supercharging. Thanks for the info.

BTW the hypereutectic piston is a cast piston with silicon added. I would guess that's what may be in our 6.4s.

Thusly not suggested for supercharging.

BTW I never use wiki as a credible source. Go to the source. I found that out doing research for WWII aircraft.
So I went directly to the horses mouth, the NASM.
 
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