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snuffyinatl

Briggs dropped valve seat

snuffyinatl
10 years ago

Model 31P777 0299 E1, exhaust valve seat dropped down, holding valve open. Can the seat be "pinged" back in, or do I get to replace the head?

Comments (6)

  • mownie
    10 years ago

    Yes, it can be peened back in place, provided it is not cracked or bent.
    Peening, or "staking" should be done using a small diameter PIN PUNCH (1/8") having a blunt tip.
    Make sure the valve seat is resting fully down in its bore (having the valve in place and valve spring assembled is best) before you begin staking.
    To stake, rest the tip of the punch on the cylinder head at a very slight angle from the valve seat, meaning that the head of the punch where you strike with hammer is about an inch away from the spot where the tip of punch rests on the cylinder head.
    This will cause the tip of the punch to only have actual contact on the edge away from the valve seat. This point of contact needs be be about 1/8" out from the valve seat bore.
    Strike the punch with the hammer hard enough to make an almost full circle mark in the cylinder head, anything over a half circle indentation is enough.
    After making your first indent, jump over to the opposite side of the seat (180 degrees) and repeat the staking, from there, move to either side at 90 degrees and stake, then jump to opposite side and stake.
    Continue the process in the same sequence until you have staked every spot in a circle around the seat, like "connecting the dots".
    The alternating strikes are to keep the pressure developed by staking from "building a wave" which might cause minor tilting of the seat if the staking was done in a simply circular fashion.

  • snuffyinatl
    Original Author
    10 years ago

    So far, so good! I went ahead and peened it, and wound up having to locktite the studs for the rocker arms, they backed off. I don't know why, I didnt remove them, but they staying put now lol. I set the valves at .004, wasnt sure what the spec was, but its running pretty smooth. I'm sure the wife will give me a full report tomorrow after she cuts the grass....I caught her looking at new riders online, and she looked kinda disappointed when I told her I had it running lol! I can't justify buying a new one over something that simple....I'm from the generation that still says "use it up, wear it out, make it do, or do without". Thanks for the tips on peening!

  • mownie
    10 years ago

    You are very close on the valve clearance specs.
    Actual specs call for .004" intake and .006" exhaust.
    And that extra .002" on the exhaust IS needed to assure the valve does not "tighten up" due to thermal saturation.
    Intake valves are bathed in a cooling draft from the induction side of the engine.
    Poor old exhaust valves get very little in cooling except for the engine oil carrying away some heat that migrates up the valve stem (and into the guide), or the little bit of heat shed into the valve seat when the valves are seated (closed).

  • walt2002
    10 years ago

    ".I'm from the generation that still says "use it up, wear it out, make it do, or do without"."

    Thought I was the only one left.

    Walt Conner

  • snuffyinatl
    Original Author
    10 years ago

    After work tonight I will loosen the exhaust valve up that extra .002.....thanks for the tips!!!

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