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Setting flathead valve lash - warm, cold, and below freezing?

Discussion in 'The Hokey Ass Message Board' started by Kevin Lee, Feb 18, 2006.

  1. Kevin Lee
    Joined: Nov 12, 2001
    Posts: 7,366

    Kevin Lee
    Super Moderator
    Staff Member

    Kind of a goofy question, but I have a book that shows clearances for Flathead tappets both warm and "cold". Got my Johnson wrenches Friday so I'm looking for time this weekend to sneak out to my garage and adjust lash.

    It's well below freezing right now and I work in an unheated garage - do I go further than the listed cold adjustment?

    Also, this is a new cam and lifters. About how long does it usually take before the valves have to be readjusted?
  2. GET OUT-of that cyrogenic chamber of a gararge!-Get into your warm bed and after ;) sleepin in til.........about noon tomorrow when it reaches that blistering 25 degree high- set the valves at their 'cold setting":D
    They are solids right?
    I only had em on chevys -but youll know when they need it- they chatter-peck and generally run a little less like they do when tight.
  3. 302GMC
    Joined: Dec 15, 2005
    Posts: 4,514

    from Idaho

    If those are the wrenches that came with a set of lifters new, be sure you let us know how you like them ...
  4. Flatman
    Joined: Dec 20, 2005
    Posts: 1,975


    Are those wrenchs the little triangular ones? I've heard they're a bitch to use, let us know how they work. It takes me about half an hour to adjust a set (not including manifold removal) but that's with a long tappet wrench. I drilled the lifter bosses 1/8" and hold them with an allen key.

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  5. Your lifters are probably an alloy along the lines of what Iskenderian used to call, "Chilled Iron."

    Couple of ways you could look at it.

    You're probably using a feeler gauge like most of us.
    Two people will end up with differing clearance settings due to they perceive feeler gauge drag differently.
    It's not a big deal and usually runs .001 - .002 different one person to the other.

    The other is the expansion rate of the lifter alloy.

    Structural steel expands at the rate of .06 - .07% per 100 degrees F.
    Note that's percent and not a measurement.

    I couldn't find a rating for cast iron, but it was noted that it was less than structural steel.

    You could run the math, but it's not necessary.
    Not to mention you'd have to factor in valve length, cam lobe etc.

    In your cold garage you're probably dealing with a temp 50 degrees F. lower than you would be if your garage was heated.
    Along with that, the temp difference between cold and hot engine is probably right at 100-120 degrees F.

    You could figure out the difference between what the recommended cold adjustment is - which the factory probably figured was 70 degrees F. or so and the ambient temp in your garage to come up with a lash figure, but I don't think it's necessary.

    The differences between hot and cold lash is what?
    .002 to .004?

    I'd use the cold setting as listed.
    Along with that, once the engine was up to temp and cam break-in completed I'd run a compression test to make sure the valves are seating ok.

    I note that the stock clearance figure cold for a 1952 flathead V8 is .014 intake and .018 exhaust.
    Cold because stock lifters are not adjustable.

    If you're really bothered by the cold and really cold lash settings, wait for ambient temps to come up or get some heat into your garage.

    You could also start the engine sans blower with one carb, break the cam in, yank the intake and check the lash settings on the now warm engine.
    If you're happy with how the engine runs and timing is where you want it, install the blower and go from there.

    One other recommendation is to get one of the Go-No-Go feeler gauges from the KD tool rack.
    There's a .002 differential between the tip of the feeler leaf and a little further in.
    That takes the difference in feeler gauge drag feel out of the picture.

    Hope this wasn't too confusing.
    Thing is, a lot of these engines were built in differing climes and if the valve settings were that critical we'd have heard about it by now....
  6. tommy
    Joined: Mar 3, 2001
    Posts: 14,763

    Member Emeritus

    What you need is a set of those intake risers, that I've only seen pictures of, that allow you to adjust the valves at opperating temperatures imediately after the engine is shut off.:)
  7. Flat Ernie
    Joined: Jun 5, 2002
    Posts: 8,398

    Flat Ernie
    Tech Editor

    It's not that critical. Some old racers used the clearances to really fine tune the cam timing - Tighter clearances is like advancing the cam & looser clearances is like retarding it!

    Set 'em using the go-nogo gauges at the cold setting.

    Once it's cranked up & broken in, pop the intake off & re-adjust (either cold or warm, your choice).

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