Reply To: QD 21 Head bolts?

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July 10, 2022 at 7:46 pm #262773
Don
Participant

    US Member

    Not sure what year a QD21 is? But, if it is older than 1961, it may have worn wrist pin bushings/rods allowing the pistons to travel higher and hit the plugs/close up the gaps. Check for writ pin slop.