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Discussion Starter · #1 ·
I recently bought a 302 block off someone. It came out of a 95 Mustang. Short and simple, after I tore it down I see all the piston ring gaps were .035-.040...
All the I formation I've read says that's too big of a gap even for power adders. Any thoughts?
 

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brand new engine?
 

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Way too much....ring gaps vary wildly depending on piston manufacturer, intended use ,etc. The general concensus is .004 per inch of bore for the top ring and .0045 for the second.
 

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I've run .065

The "general consensus" for decades was to run the "second compression" ring tighter than the top. I had a conversation with a diesel mechanic that convinced me otherwise in 1992, recommended +.003 on the second from then on. About 1998 everyone else came around too.

Following the general consensus is stupid.

What we're discussing here is the "hole" in one ring that is .040 x whatever the ring sticks out of the ring groove (which ain't much). How much air can leak out of there with 60 lbs of pressure in about two milliseconds.

It's a head....not a hat rack.
 

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.04 is definitely overkill, and .035 isn’t much better.
 

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I said it was overkill, not that it wouldn’t run. I wouldn’t feel necessary to gap them that big. I also wouldn’t feel it necessary to change it if they were already that big, so there’s that.
 
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As said already it will run. I would buy a set of rings and redo them personally, especially if it's staying N/A
 

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Just to throw another angle to this, if the engine has OEM cast hypereutectic ('94-'95 came with hyper from what I've read) or rebuilt with Keith Black hypereutectic pistons, those end-gaps are fine. KB recommends 0.028" for N/A, 0.032" for N2O/supercharged in a 4" bore. You're not the 1st person to find 0.035" gaps when they've disassembled their engine.
 
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Discussion Starter · #13 ·
Just to throw another angle to this, if the engine has OEM cast hypereutectic ('94-'95 came with hyper from what I've read) or rebuilt with Keith Black hypereutectic pistons, those end-gaps are fine. KB recommends 0.028" for N/A, 0.032" for N2O/supercharged in a 4" bore. You're not the 1st person to find 0.035" gaps when they've disassembled their engine.
They're Hypereutectic Pistons
 
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