Piston ring side (axial) clearance - higher than spec?

[Nut124]

My new pistons and rings show axial clearance much higher than shop manual and google.

Top ring: 0.006, Middle: 0.007, Oil ring: 0.005

Is this a problem? If so, how much so? Not much I can do about it.

The piston that came out of the block had top ring clearance at 0.010.

These are OEM(?) cast alu pistons for Fiat twincam.

[Nut124]

Never mind, I made a dumb mistake. I was using a metric feeler gauge and misread it as inches. The 6 thou clearance was actually 0.06mm or 0.0024".

All is good.

[swampbuggy]

There was a song in the 70's........everybody plays the fool sometimes, theres no exception to the rule. And this is true, we are human beings and make mistakes. Mark H.

[MadBill]

There have been many, many near and actual disasters caused by flubbed Metric/Imperial conversions (or lack thereof...). One I really like (probably because of the alliterative name) is The Gimli Glider, an Air Canada 767 that in 1983 was fueled in litres instead of gallons and ran dry mid-flight: https://en.wikipedia.org/wiki/Gimli_Glider

[Geoff2]

Actually Bill, the aircraft was fuelled by fuel weight, not volume, & the error occurred after a recent switch from pounds to kilograms. I believe an airport was named after the Captain of the aircraft....

[Nut124]

There have been many, many near and actual disasters caused by flubbed Metric/Imperial conversions (or lack thereof...). One I really like (probably because of the alliterative name) is The Gimli Glider, an Air Canada 767 that in 1983 was fueled in litres instead of gallons and ran dry mid-flight: https://en.wikipedia.org/wiki/Gimli_Glider

Interesting story. And a happy ending. Thanks for sharing.

[Dan Timberlake]

If the rings really had that much side clearance I'd speculate there'd be problems with ring sealing and even oil control. MAybe even "ring life."

The prehistoric factory wear limits of 0.006" or so was for for ring groove wear which is probably "worse" than .006" clearance in a "perfect" groove.
In them days there was not such expectation for long term service, infinitesimal oil consumption, or concerns for strict emissions or fragile emissions equipment.

The .010" factory wear limit for a 1968 Street Hemi cylinder taper still takes my breath away.

street hemi engine specs.PNG

[Geoff2]

That's the taper limit, bore wear is 0.005".

[pdq67]

I stuck a .015" feeler gage down the sides of the cheap W/JCW 1/8" over 283, 1/8" 1/2 round domed cast aluminum, steel-strutted, pistons in my old junk301.

Sure it knocked hammered and smoked BUT it still went above 7,000 rpm fine

W/JCW's $39.95 finest...

Oh, my old roundy-round engine builder/Machinist turned the pistons around backwards on the rods to put the .060" thrust offset in a better position..

pdq67

[MadBill]

Actually Bill, the aircraft was fuelled by fuel weight, not volume, & the error occurred after a recent switch from pounds to kilograms. I believe an airport was named after the Captain of the aircraft....

Yes, per the link I posted, there were both mass and volume measurements involved, plus about four other contributing factors.

Canada does have a Pearson airport, but it's named after Lester B. Pearson, Prime Minister from 1963-68.

[Kevin Johnson]

There have been many, many near and actual disasters caused by flubbed Metric/Imperial conversions (or lack thereof...). One I really like (probably because of the alliterative name) is The Gimli Glider, an Air Canada 767 that in 1983 was fueled in litres instead of gallons and ran dry mid-flight: https://en.wikipedia.org/wiki/Gimli_Glider

I like Imperial gallons because I get better mileage.