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flat or dished pistons


red13

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I would plan on a bore. 

Stuffing 83.xx into a honed 83.xx hole is merely a band-aid. 

 

Boring a block to fit oversized pistons is more like having a new block. 

 

 

 

For the price of machine work you can just source an L20B for more power out the box. 

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The piston to bore clearance is 0.001" to 0.0018" or roughly 1 to 2 thousandth of an inch. Newsprint is about 2 thou. Stock pistons are not 83mm, they range from 82.985mm to 83.035mm and the same goes for the bore. No bore is exactly 83mm. Those that are slightly over get a 'larger' piston to maintain that 1 to 1.8 thou clearance. Definitely measure the bore in 6 places and check for oval and taper and over size if needed. Oversize pistons cost the same a stock ones.

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Those aren't even stock pistons.  I don't know what they're from.  L-series pistons don't have valve cutouts, and those aren't Z-series pistons either.

 

Flattops would increase compression, and with that semi-closed chamber 210 head might increase it so you'd need to run higher octane fuel to prevent detonation.  But maybe not.  Those valve reliefs had your compression a bit low to begin with.

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Stock 210 L16 head...

 

head210L16.jpg

 

210 head with stock 7.01cc dish pistons...... 8.58... with closed head... 8.21... with open head.... 6.72

210 head with true flattops.......................... 9.75... with closed head... 9.29... with open head.... 8.63

 

 

.

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210 head, closed chamber (41cc) and open chamber (45.2cc). Three heads. There was a closed chamber 210 head but it's almost the same as the regular 210 for size.

 

The A87 closed or the SSSL16 219/V912 head actually drops the compression on an L16 unless you have the flattop pistons to go with it. An open chamber U67 head drops a stock L16 into the 6s.

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