Piston Ring movements
Piston Ring movementsI am rebuilding a once frozen 67 305. My top piston ring runs free, lots of slack. My middle and lower piston rings are tighter than a drum to the piston. No slack, won't turn, etc. Having already broken one piston ring out, my question is: Are the lower two piston rings supposed to have slack? I dropped by the local Honda dealer earlier today, who assured me that piston rings have slack. As the motor was made before the kid who gave me this advice, I thought I would get a second opinion.
GW - You're into some pretty high precision stuff here so I'd be careful with sharp tools and abraisives. Yes the rings should all be "free" in their respective grooves. To get the old rings out, I'd try soaking in carb cleaner overnight. If still really stuck, clamp them in a vice with some wooden blocks and warm them up as hot as you can get them with a good heat gun (not a torch). They sometimes come out in pieces, but that's OK because you shouldn't reuse them anyway. Big pieces can be good tools to pry out the next piece. Be patient, those pistons are worth a few bucks in good shape. As far as slack goes, the shop manual gives "Piston ring & groove" clearances as follows:
Top Ring standard: .002"-.003" repairing limit: .006" Second Ring standard: .001"-.002" repairing limit: .004" Oil Ring standard: .001"-.002" repairing limit: .004" "Standard" would be a new engine, and "repairing limit" is the maximum. That clearance is intended to let hot high-pressure combustion products leak around to the back side of the rings and force them against the cylinder. The rings also have a right-side-up that has a tiny marking near one of the ends. -48
Many thanksI am now suffering from exposure to brake cleaner fumes.....ah, the joy.
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