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Thread: Adjusting flathead valves

  1. #1
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    Adjusting flathead valves

    OK, after 41 years of owning my ?36 Pontiac I am going to attempt a valve adjustment on my own. Here?s what I think I know about how to do it:

    ? Don?t even try to adjust them when hot (the exhaust manifold is right on top of them and I would surely fry my arms).
    ? Leaving them a little loose is better than getting them too tight and risk burning them.
    ? Adjust them .002? over when cold. My specs are 9-11 hot, so I?m thinking 12 would be a good middle setting.

    The problem I haven?t figured out is how to know when the valves are in the right position for adjustment. #1 is easy: find TDC (when both valves are closed, the lifters free and the gap the largest), then adjust. But how do you accurately and easily find TDC on the other five cylinders? Turn the engine over by hand and watch the lifters until they seem to be in the right position? (tedious) Use a compression gauge? Seems like it would be a lot easier if they had marked all cylinder TDCs on the flywheel.

    How did they do it in the old days? My Flat Rate manual says the time allotted to this job was 30 minutes. I?ll be lucky to get one done in that time I?m sure!

    Thanks.
    Bob Shafto

    1936 Pontiac Master Business Coupe 26-2607A
    1936 Pontiac Cabriolet 26-2667A
    1966 Ford Galaxie 500 Convertible

  2. #2

    Re: Adjusting flathead valves

    i did the ones on my packard 288 flat 8 while it was running, put a floor fan behind you blowing across the engine and the heat wont be a issue unless you lean against the manifold. an easy way to tell if they are to lose is to just use your ears and a thick piece of construction paper. if you can hear a bit of ticking slide the construction paper between the tappet and valve stem if it stops ticking then that one is probably above specs then use your feeler gauge and adjust. its not really a "by the book" way of doing it but has always worked for me without any issues. id be a bit iffy about "guessing" a good cold measurement as im sure the expansion could be different among the valves.

    just a thought
    tom
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  3. #3
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    Re: Adjusting flathead valves

    The adjustment 9 - 11 does not mean is 9 or 10 or 11. It means a .009 feeler will pass through but a .011 will not. This used to be referred to as go/nogo. There used to be feeler guages available that had the thinner measurement on the end of the guage and the thicker amount half an inch up from the end. In this way it was easy to set the tappets. If the end of the guage went in but the next step[ didn't they were set right. The only proper way to set them is with the engine running. You can slow down the idle until you can almost count the fan blades and away you go. After a few tappets you get the hang of holding the feeler guage and one wrench in one hand an two wrenches in the other. It really is quite easy.

  4. #4

    Re: Adjusting flathead valves

    I have a 1931 Hupmobile flathead and selected a mechanic from a local antique restoration shop to adjust the valves. The mfg spec adjustment is 8 thousands when the engine is hot. Knowledgeable people on Hupmobiles said the valve clearance should be set to 12 thousands when set cold. This creates a slight tappet sound when the engine is running. It is advisable to have a slight tappet sound.

    Before the mechanic came to my house, I removed the Carb, Intake/exhaust manifolds, and the valve adjustment covers. I also removed the spark plugs, permitting zero compression for easier turning the engine over using the fan blades. On my car, the valve adjustments are below the manifolds and you can not see the valve adjustment nuts. This is why I removed the manifolds.

    You will need a feeler gauge and the correct size tappet wrenches. Sears sells a set of 4 for about $26.00 or you can grind regular wrenches down to be narrow enough to fit the adjustments nuts.

    Manually turning the engine over till both the lifters are off the lobs for the cylinder you are adjusting worked for me. This is easy if you have two people. My engine has 3 nuts to adjust the valve lifter and lock each valve. The mechanic is about 20 minutes from my house and his bill was 2 hours including travel time.

    After he left, I reinstalled the valve adjustment covers, manifolds, the carb, and drove out of the garage. I am not a great mechanic but now that I have seen it done, I could do it myself the next time. In reality, I will have him do it a gain, I am just a little lazy sometimes.
    JSD

  5. #5
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    Re: Adjusting flathead valves

    Thanks everyone for your responses. I envy your willness to adjust them while hot and running! That just seemed like too much for me.

    After thinking about it awhile the obvious answer to my question about knowing when you are TDC on every cylinder occurred to me: remove the distributor cap and watch until the points are high on the cam, adjust the valves as per the timing order. Duh!

    It worked great. My manual says adjust to .011 for sustained highway driving. I do some highway, but not usually sustained, so went for .010 + .002 over for being cold and they sound great. A pretty easy job once you get the hang of it.
    Bob Shafto

    1936 Pontiac Master Business Coupe 26-2607A
    1936 Pontiac Cabriolet 26-2667A
    1966 Ford Galaxie 500 Convertible

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