Vintage Gm Chevrolet Motors Checking Piston Rings
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By Wayne I Haddad
Vintage auto enthusiasts will tell you that ‘its fun’ working on older simpler vehicles and motors. Today’s cars and trucks are often so cramped to work on and the electronics are not only complex but in many cases sealed electronic units that cannot be repaired, they have to replace. On top of that once you purchase the part – it’s yours and non-repairable at the dealer, big box store or at an online specialty shop or eBay. You cannot blame these dealers’ parts departments and retail / online outlets. Today’s electronics in automobiles are just so delicate and easily damaged by the smallest spark of static electricity or power surge. That is why older vehicles can be just so much fun to work on. They are relatively simple mechanical devices which at the most for electronics parts – have a lead car battery, points, plug a distributor cap and condenser.
Yet when you are rebuilding older Chevrolet and GM motors how do check piston pins?
It is often difficult to determine whether a piston pin requires replacement. The voice of experienced mechanics who have much time and expertise under their belts with these engines, their characteristics, diagnosis and foibles will advise and teach you that in general, a piston ring knock will sound much worse than a loose valve tappet, and in many cases is worse when the engine is stone cold, than after it has reached operating temperatures. Imagine the decibels that can emanate from a cold motor in 40 degrees northern Canadian winter season. However when the car or truck has traveled a distance sufficient to require replacement of piston rings and bearings, it will be surely overall poor economy not to replace the piston pins also. Furthermore when new piston rings have been installed, and particularly when pistons have ‘expanded’, piston pins with only a slight amount of excess clearance will cause a knock. These knocks will some cases disappear after the piston rings have been ‘run in’.
When examine the condition and conditions of the piston rings, any appreciable looseness or wear is sufficient cause for rejection. An inexperienced mechanic will sometimes confuse side play of the pins and the piston boss with pin wear.
The method of judging the ‘fit’ of new piston pins will depend largely on the method of fitting the new pins. When a hone is used to fit the pins, they will seem to be relatively loose. If a reamer is used for fitting the pins, they will appear to be tighter than if they had been fitted by the hone method.
When the hone method is used, the end of the rod will drop quickly of its own weight when the assembly is held by the piston. If the reamer method is used to fit the pin, the rod will not drop of its own weight when the assembly is held by the piston.
These are lessons that perhaps you might not ‘read in a book’ or be taught in a course on working on or with vintage engines. They are invaluable tips. Have fun with your auto restoration projects especially old Chevrolets.
About the Author: Wayne I. Haddad Truck Sales Vancouver BCAuto Sales Vancouver CanadaTrucks for Sale Surrey British Columbia
Source: isnare.com
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