Show I Uy Dy ISn ElJ Selene C Editor KEA liEA Sef CC ONE ONI kNE of tho the most mo t elusive and and f costly co knocks knock In the th engine le Is that caused by loos loose loo piston Its It's It what Is I called a piston pitton slap but Id III heard almost aj as II a a knock especially while the tho engine Ja is J cold coldS As S the th engine worms warms up the knock disappears disappear However Howe even after oCter its 1111 It dl ap I Its effects are arc felt In n lower power and less leas mileage from the fuel What happens Is this A loose piston generally means too much clearance between cylinder der wall and piston The Tho result Is that part of the fuel tuel that should burn up completely In the tho chamber above o the piston head seeps down don down through the space and Into tho the crankcase Thero It di dilutes 1 lutes the oil lis fie citing efficiency and playing havoc ha with the cylinder walls wall and bear bear- bearings ings inga At the tho same Bamo time the oil from tho Iho crankcase Is pumped up through the apace paco between vision piston and aud cylinder wall and into the combustion chamber There the heat o of combustion burns It enough to ca cauro cu u o a a heavy layer of carbon to result The Th diluted oil scores the tho cy- cy cy- cy cyl cylinders inders And the widening space offers room for the flames of com com- combustion combustion bustion to jet get In and further In Jur In-Jur cure Jure tho the cylinder lIs l wall The walls get Bet out of p round under this scoring and and burning process and compression Is great great- greatly greatly ly creat-ly ly diminished You may become suspicious of C pIston slap lap when the tho ha engine knocks ks only when cold eold when It loses compression and fuel Is b be- be being b Ing wasted waited In less les mileage While the tho engine engino is hot how over ever you need ned less l u compression and ond your fuel combustion Is al- al almost aimo mot 1 mo most t complete Put the two and two together then make certain by the th follow follow- following Inc follow Ing test Remove the tho spark park plug plus from the first cylinder pour In about sn n eighth of a pint of o heavy oil then crank the engine by hand hond slowly until the tha oil works work In He Replace lace the spark park plug and start the engine cn lne If H the same sarno knock occurs occur It Isn't a a- a piston knock at least In that cylinder cylinder It r It If It doesn't doc nt occur for a shot short while and then begins after a few revolutions of or the tho engine you may bo be sure suro uro tho trouble Is In that cylinder and tho piston is 18 t the tb cause This Thin may be repeated with theother the theother theother other cylinders The remedy for tor thi this trouble I of the cylinder If It It hap hap- happens happens hap hap- happens pens to bo be scored over or out of oC round end and fitting of oversize pia tons pit tons and nd rings l I lIf i If It the piston slap lap Is caught at its first stage the same sarno amo piston may be used except that It he b lapped In 10 or worn In so o asto as asto asto to polish down clown the cylinder wall wull to smoothness and ond new piston rings s 1 bo be 0 applied At times the connecting rods may be out of oC alignment caus- caus causIng causing caus Ing the tho pistons to strike triko the tho cI cI- cI cyl cylinder inder finder walls unevenly It If clearance Is correct and the cylinder walls look smooth th the connecting rode rod should be bo checked UP for Cor alignment That r operation by II a high hl h grade crado mech mech- mechanic mechanic anic Copyright 1827 1 NEA EA Service |