Re: 70's relic destroyed
Posted by shinyribs on Jul 08, 2012; 3:35am
URL: http://vintage-and-classic-hondas.81.s1.nabble.com/70-s-relic-destroyed-tp4024444p4024660.html
Piston slap is usually from a piston that is too small for its bore. Sometimes they are just ovaled,which is usually from extreme skirt wear. Yeah,alot of engines do it and live just fine,but it is a sign of a loose slug in a hole. Severe slap can knock a skirt off ( done it! ) or if nothing else,it can cause the rings to oval (from the piston wobbling on the wrist pin ) and cause oil control issues and loss of compression. Severely ovaled rings can wrap around the ring lands if the rocking gets bad enough. We had a 514 cu in Indy headed Mopar 440 that slapped real bad when cold from the cheap forged pistons that came with that kit. The owner of that engine wouldnt let it come up to full op temp before running it and wrapped a few rings up one day. When they wrap,if you are lucky,they will eat your cylinders alive. If not lucky,like that guy with the 514,they will chunk off the top ring land and wedge it nicely in your head. It actually spat on piece of ring thru an intake valve and the carb and it landed on the intake manifold! Crazy! Oh yeah,he never ran an air cleaner either
Would I tear an engine down just because of piston slap? NO. Not unless it was puking oil or really losing compression. If the slap start getting a little louder,then yes. That 350 that tossed a shirt tried to warn me it needed attention,but I ignored it.Luckily the skirt just fell in the pan and didnt try to lock up anything.
Alot of forged pistons swell much more than cast do. Which is why most oem's never used many forged piston until somewhat recently. The technology has improved a bunch. EVERY (serious) drag engine I have ever owned slapped pistons (all 8 ) at idle until full warm. Nature of the beast,dont rev it til its ready and good and warm.
Piston slap is not good,but it aint all bad
URL: http://vintage-and-classic-hondas.81.s1.nabble.com/70-s-relic-destroyed-tp4024444p4024660.html
Piston slap is usually from a piston that is too small for its bore. Sometimes they are just ovaled,which is usually from extreme skirt wear. Yeah,alot of engines do it and live just fine,but it is a sign of a loose slug in a hole. Severe slap can knock a skirt off ( done it! ) or if nothing else,it can cause the rings to oval (from the piston wobbling on the wrist pin ) and cause oil control issues and loss of compression. Severely ovaled rings can wrap around the ring lands if the rocking gets bad enough. We had a 514 cu in Indy headed Mopar 440 that slapped real bad when cold from the cheap forged pistons that came with that kit. The owner of that engine wouldnt let it come up to full op temp before running it and wrapped a few rings up one day. When they wrap,if you are lucky,they will eat your cylinders alive. If not lucky,like that guy with the 514,they will chunk off the top ring land and wedge it nicely in your head. It actually spat on piece of ring thru an intake valve and the carb and it landed on the intake manifold! Crazy! Oh yeah,he never ran an air cleaner either
Would I tear an engine down just because of piston slap? NO. Not unless it was puking oil or really losing compression. If the slap start getting a little louder,then yes. That 350 that tossed a shirt tried to warn me it needed attention,but I ignored it.Luckily the skirt just fell in the pan and didnt try to lock up anything.
Alot of forged pistons swell much more than cast do. Which is why most oem's never used many forged piston until somewhat recently. The technology has improved a bunch. EVERY (serious) drag engine I have ever owned slapped pistons (all 8 ) at idle until full warm. Nature of the beast,dont rev it til its ready and good and warm.
Piston slap is not good,but it aint all bad
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