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Thread: 25 Ford T valve and valve seat pitting evaluation

  1. #1

    25 Ford T valve and valve seat pitting evaluation

    We took the head off this old T and found the valves just packed with carbon, creating serious compression problems. (I think I know how the carbon got there, so no need to theorize with that aspect of this.)

    I'm no experienced hand here, so could use some wet-nursing. Are there any good photos of valves and valve seats showing how bad they can be and still lap in without going to the machine shop?

    I guess I could clean everything up and replace the valves, springs, etc., with lapping compound and just see if they will lap in OK.

    I'd rather not do that, though, if I had some way to evaluate my problem child ahead of time so I could if necessary just buy a new set of valves, or new exhaust valves if I could get away with that, but then.....

    .....I don't know how to make them fit the old seats without a trip to the machine shop.

    I may be stuck with the machine shop, but would like you guys to show me a way out. I'm sure you've NEVER confronted this attitude, have you?

    Thanks again,
    Stephen W. Davis
    1915 Dodge Bros (two of them)
    1922 DB
    1926 DB
    1928 DB Victory Six
    1935 Chrysler Airflow
    1942 Plymouth Spl Deluxe
    1948 Dodge
    1951 Chrysler Imperial
    1952 Chrysler Windsor
    1953 Plymouth Cranbrook
    1964 Chrysler 300K
    1966 Dodge Charger
    ......and a bunch of non-MOPARs

  2. #2
    Senior Member F&J's Avatar
    Join Date
    Dec 2008
    Eastern Connecticut

    Re: 25 Ford T valve and valve seat pitting evaluation

    You really can't lap new valves into a worn seat that you didn't regrind.

    So... if the engine just needs to run.. .. keep each USED valve in the same seat. Lap each one after getting rid of the carbon.

    You can test your work on each valve after lapping by running the valve on a bench top wire wheel to shine up the lapped surface. Then put a tiny bit of compound on to relap and then see how much shine is gone, and if there is a spot that is not seating.

  3. #3
    Senior Member jan arnett (2)'s Avatar
    Join Date
    May 2008
    ft. Thomas, Ky

    Smile Re: 25 Ford T valve and valve seat pitting evaluation

    Remember that a Model T was what the term "Shade Tree Mechanic" was created for. The Model T has a low compression and you can not really do anything wrong. I would only not use the original ones if one of these conditions have occured.
    1. Bent Valve.
    2. The valve stem is pitted
    3. The bottom of the stem is mushroomed.
    4. The valve stem is to short and you can not get the proper gap between the stem and the lifter. If you have adjustable lifters then this may not be an issue.

    If you have valve lapping tools and know how to use them then do not read any further. Looking at the number of cars you have then I am sure you can handle it just make sure that you use a valve lapping tool and not a suction cup. If you have not done it before remember that after you lap the valves you will have to grind the valve stems to get the proper clearance between the stem and lifter. I also use drill rod as a retainer pin.

    Have a nice day.

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