Excessive piston wear?
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Cross-Country
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Excessive piston wear?
I'm disassembling my 1973 460 engine block for a rebuild, and did cylinder and piston measurements today.
Cylinder diameters range from 4.36" (at the base) to 4.367" (just below the ridge of the most worn cylinder). This seems reasonable to me.
However, piston diameters range from 4.33" to 4.34". I am measuring diameter between the rings of the piston, not at the top where wear is more evident.
Is this difference in wear (much more to the pistons than the cylinders) usual?
It seems like the pistons are extremely worn and need replacement, but the engine was running decently well the last time it ran (a few months ago). Is that much piston to bore gap within engine tolerances?
Am I measuring incorrectly or missing something?
If not, could I get by with an hone and stay with stock piston size? Or is 0.007" too much and needs to be bored out?
Cylinder diameters range from 4.36" (at the base) to 4.367" (just below the ridge of the most worn cylinder). This seems reasonable to me.
However, piston diameters range from 4.33" to 4.34". I am measuring diameter between the rings of the piston, not at the top where wear is more evident.
Is this difference in wear (much more to the pistons than the cylinders) usual?
It seems like the pistons are extremely worn and need replacement, but the engine was running decently well the last time it ran (a few months ago). Is that much piston to bore gap within engine tolerances?
Am I measuring incorrectly or missing something?
If not, could I get by with an hone and stay with stock piston size? Or is 0.007" too much and needs to be bored out?
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The block is iron, the pistons aluminum. No surprise your pistons are worn in a 40 year old motor.
The numbers you posted indicate piston to bore clearances of .027 to .030. How are you measuring bore? Based on this, you are measuring the pistons in the wrong place--they say measure down on the skirt:
Probe Industries - High Quality Forged Pistons, Shaft Rockers, Main Girdles, Stud Girdles, Engine Kits, Crankshafts and Connecting Rods for Buick, Chevy, Ford, Chrysler, Pontiac, Oldsmobile and Sport Compact Applications. - 866-718-6267
http://www.kb-silvolite.com/test/***...structions.pdf
From what I gather, .007 would be too much for stock cast pistons. It would work, but might give you some piston slap, a shorter life, possibly oil consumption, and worse case, real short life with broken ring lands due to the piston rocking in the bore. .003 would be a better number methinks.
But, measure things as per the above, and then you will have better numbers to compare.
Boring discussion:
https://www.ford-trucks.com/forums/8...-92-460-a.html
The numbers you posted indicate piston to bore clearances of .027 to .030. How are you measuring bore? Based on this, you are measuring the pistons in the wrong place--they say measure down on the skirt:
Probe Industries - High Quality Forged Pistons, Shaft Rockers, Main Girdles, Stud Girdles, Engine Kits, Crankshafts and Connecting Rods for Buick, Chevy, Ford, Chrysler, Pontiac, Oldsmobile and Sport Compact Applications. - 866-718-6267
http://www.kb-silvolite.com/test/***...structions.pdf
From what I gather, .007 would be too much for stock cast pistons. It would work, but might give you some piston slap, a shorter life, possibly oil consumption, and worse case, real short life with broken ring lands due to the piston rocking in the bore. .003 would be a better number methinks.
But, measure things as per the above, and then you will have better numbers to compare.
Boring discussion:
https://www.ford-trucks.com/forums/8...-92-460-a.html
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