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Registered
Join Date: Aug 2018
Location: Chicago
Posts: 55
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Is this piston usable
A friend of mine has a set of 2.7RS pistons and one was appearently dropped at some point. Is it usable as-is or is it junk?
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09-06-2020, 02:38 PM
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Puny Bird
Join Date: Nov 2002
Location: Port Hope (near Toronto) On, Canada
Posts: 4,566
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Hard to tell from a pic, sometimes you can fix aluminium by going at it sort of like a paintless dent repair guy. Left over high spots can be smoothed with a small file.
Is it a ding or a divot? A RS piston I'd try to save.
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'74 Porsche 914, 3.0/6 '72 Porsche 914, 1.7, wife's summer DD '67 Bug, 2600cc T4,'67 Bus, 2.0 T1 Not putting miles on your car is like not having sex with your girlfriend, so she'll be more desirable to her next boyfriend. |
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09-07-2020, 03:57 AM
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I would take the gamble....
Before taking a file to it, take a small hammer and try to tap the topside back down. Most om the aluminum is still there it has just been displaced. Then check so its round and that the ring grove isn't tight.
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Magnus 911 Silver Targa -77, 3.2 -84 with custom ITBs and EFI. 911T Coupe -69, 3.6, G50, "RSR", track day. 924 -79 Rat Rod EFI/Turbo 375whp@1.85bar. 931 -79 under total restoration. |
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09-07-2020, 04:37 AM
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Join Date: Jun 2009
Posts: 1,238
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That piston is fine. Make sure nothing protrudes outside the circumference of the crown and as has been stated, tap or file down the raised part. Also confirm that the blow didn't close up the ring land, and doubt if it did.
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09-07-2020, 05:06 AM
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It's a 914 ...
Join Date: Jan 2008
Location: Ossining, NY
Posts: 4,698
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It looks slightly raised on the top portion. Maybe on a few thou, but this will narrow the deck height at that one spot. I'd at least want that to be even with the rest of the perimeter around the top of the piston.
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09-07-2020, 06:15 AM
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Join Date: Mar 2003
Location: Edmonton
Posts: 697
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Ring land pinched?
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Matt B '73 911E |
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09-07-2020, 09:06 AM
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Registered
Join Date: Feb 2004
Location: denver
Posts: 1,145
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The critical part of the piston is top ring land. If it was pinched from dropping or you pinch by hitting with a hammer as others have suggested then it would need to have the top grove re-machined to correct clearance. If ring land is in spec file any high spots from drop and call it good.
john |
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09-07-2020, 11:14 AM
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Registered
Join Date: Aug 2018
Location: Chicago
Posts: 55
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Thank you all for the replies/advice. I'll measure the top ring gap and go from there.
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09-07-2020, 11:21 AM
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Registered
Join Date: Sep 2015
Location: Costa Rica and Pennsylvania U.S.
Posts: 3,301
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piston dent
C,mon look at the picture.That was dropped from the side & not the top.The piston to head clearance is a little less.Big deal.Do not touch & the top ringland clearance is fine but measure it anyway.Ciao Fred
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09-07-2020, 05:05 PM
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Under the radar
Join Date: May 2007
Location: Fortuna, CA. On the Lost Coast near the Emerald Triangle
Posts: 7,129
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I would not use a hammer on it. One deformation of aluminum is probably OK. If you do more bending or reshaping you will chance forming a crack.
If it was a wheel I would not hesitate to use a hammer. On a piston, no way. Use a file to even off the top. Check the ring side clearance and call it good.
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Gordon ___________________________________ '71 911 Coupe 3,0L outlawed #56 PCA Redwood Region, GGR, NASA, Speed SF Trackrash's Garage :: My Garage |
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09-07-2020, 05:34 PM
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1977 Porsche 911 Targa 2.7s
My Garage
1971 Porsche 911
Baja Bug
