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Thread: How many miles to seat piston rings?

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  1. #1
    Jedi Hopeful
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    Newnan, GA
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    How many miles to seat piston rings?

    Recently rebuilt engine. I'm at 500 miles and am re torquing the head. The engine runs very well with no noticeable oil consumption. I do get several drops of oil out of the road vent tube over night after a 25 mile drive. How long does it typically take to seat the rings? I'm running Valvoline VR1 20w50. Steve Baker
    I own 1958 TR3A TS 26005L and have the privilege of working on 1960 TR3A TS 65587L.

  2. #2
    Yoda poolboy's Avatar
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    Oct 2007
    S.W. Mississippi
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    Re: How many miles to seat piston rings?

    I did a series of compression test. Do one now at 500 miles; then do another at 1000....continue on at intervals of your choice if you want.

  3. #3
    Yoda CJD's Avatar
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    Re: How many miles to seat piston rings?

    It depends on the type rings and cylinder finish.

    Chrome rings in a cast iron cylinder will take at least 1000 miles of street driving.

    Standard cast iron rings on a relatively rough honed cylinder (you can easily see and feel the hone marks on the cylinder wall) take at least 500 miles.

    molly rings in a fine honed cylinder (cylinder walls look like a mirror) will seat as soon as you do the bedding procedure below.

    To bed new rings, take the car out where you have room to alter speed without getting rear ended. With the car in 3rd gear, accelerate under full throttle from about 20 to about 60 mph. Then take your foot off the throttle and allow it to coast back to 20 mph, still in 3rd gear. Repeat about 10 times and you have bedded the rings. The accel loads them against the cylinder to mate them...the coasting provides vacuum to draw oil up and cool them.

    Finally, if you are using parts supplied from the big have cast iron rings, so 500 miles is probably your answer. Oil usage should drop to nearly nothing by that time.

    1955 TR2

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  5. #4
    Luke Skywalker
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    Re: How many miles to seat piston rings?

    I don't think a couple of drops from the vent pipe is unusual although it might get better after the rings wear in. Might not too.
    1960 TR3A TS73117 (under endless restoration, owned since 1964)
    1959 TR3A TS58023 (in case I never finish the one above)
    1969 Triumph Herald 13/60 (a whim)
    1970 Lotus Elan Plus 2 /0023/N
    1992 BMW325IC (fun to drive)


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