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Technical Busted valve spring or springs?

Discussion in 'The Hokey Ass Message Board' started by 50 Merc Man, Aug 3, 2020.

  1. 50 Merc Man
    Joined: Aug 2, 2020
    Posts: 432

    50 Merc Man
    Member

    Here’s the deal hot rodders,
    My 50 Merc is flattering out at top end, no horsepower at all, seems to be sputtering a bit too, I thought possibly it could be the choke sticking ? Fouled plug? Or even a dirty or clogged fuel filter?
    Any one of those would be ok, but I’m looking or thinking worse case scenarios here. Valve spring
    Any ideas anyone?


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  2. 41hemi
    Joined: Jul 2, 2007
    Posts: 1,000

    41hemi
    Member

    I will recommend that you check your timing and the vacuum advance. You want all your advance coming in at higher rpm's.
     
    VANDENPLAS likes this.
  3. MantulaMan
    Joined: Jun 19, 2018
    Posts: 40

    MantulaMan

    Stick a vacuum gauge on it. That will tell you if any valves are sticking.[​IMG]

    Sent from my SM-A105G using Tapatalk
     
  4. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 5,217

    2OLD2FAST
    Member
    from illinois

    Be aware that this ^^^^^^^^ only applies to an engine with ," stock" or very mild cams , most performance cams would not produce the same results ......
     

  5. I like using a vacuum gauge, great for adjusting carbs too. Other things to check are the plugs themselves, on the outside a compression test depending on how the plugs look. What is the age of the fuel filter? I replace mine once a year regardless of how far I drive. Fuel lines can collapse with the great gasoline we have to use.
     
    olscrounger likes this.
  6. 302GMC
    Joined: Dec 15, 2005
    Posts: 7,856

    302GMC
    Member
    from Idaho

    The first thing you do when your car don't run right is check the compression. Do it dry, then give each hole 4-5 squirts of oil and check it again ...
     
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  7. ekimneirbo
    Joined: Apr 29, 2017
    Posts: 4,217

    ekimneirbo

    When a flathead backfires or sputters............is that flatulence ?:D:D:D
     
    Last edited: Aug 3, 2020
  8. Mike VV
    Joined: Sep 28, 2010
    Posts: 3,029

    Mike VV
    Member
    from SoCal

    Yes...weak springs will most definitely limit top speed to something lower than with good springs.
    In most cases, old, well used springs may well be the culprit.

    This assumes that the rest of the engine is right. Proper fuel pressure, an ignition "system" that is in good shape.

    Sounds like you may well be looking into the whole engine -
    1. Points adjustment.
    2. Overall ignition timing.
    3. Spark plug wires.
    4 Coil.
    5. Fuel pressure (filter(s).
    6. Fuel level in the bowl(s).
    7. Valve spring tension.
    8. Spark plugs (how old, correct gap).
    9. How much rpm can the cam provide ?

    And more...

    Mike
     
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  9. If you've been used to anything late model or even a Small Block Chevy understand that Top End shows up much sooner in a Flat Head. A Big Inch Flathead is still less than 300 inch and I doubt your anywhere close to that. She sure is pretty under the Hood though, wish mine still looked like that. I think I have Fixed mine to Death.
     
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  10. 50 Merc Man
    Joined: Aug 2, 2020
    Posts: 432

    50 Merc Man
    Member

    Hey Mike, I know it’s been a long while since I posted this, but I am a little unsure of checking the timing on a flathead, hook up light to number one right? Is it like a small block Chevy at all?
    I just sent off for a new set of plug wires, I’m hoping that’ll solve the sputtering issues


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  11. Mike VV
    Joined: Sep 28, 2010
    Posts: 3,029

    Mike VV
    Member
    from SoCal

    Correct, connect to number cylinder number's plug wire.
    make sure the timing marks are clean and visible.
    Make sure all of the timing lights harness is away from the fan and belt, start engine.
    Check the initial timing, damper to pointer.
    Advance or retard to suit what you want.

    Yes, basically like any other engine, like a small Chevy.
    You might want to put a few more degrees of timing lead in than the "book" says. The original manuals are always a few degrees short of the pest performance available.

    Make sure that your spark plugs are also in good condition, and that you have no vacuum leaks.

    Mike
     
  12. Truck64
    Joined: Oct 18, 2015
    Posts: 5,325

    Truck64
    Member
    from Ioway

    First check compression, always pg. 1 para. 1 in the Tune-Up manuals. Ever notice that? Then a vacuum test with a vacuum gauge on pg. 2 thru 4. It will show broken, or weak valve springs too, if you know what to look for.

    I'd think they'd have to be really lunched, but weak springs can act as a natural rev limiter. Apparently what happens in this situation is the valve starts to bounce repeatedly before staying closed for good, this limits power in the case of the intake valve.
     
  13. Budget36
    Joined: Nov 29, 2014
    Posts: 13,174

    Budget36
    Member

    It’s a flathead, right? So not ever having a hot one, keep in mind my reply

    FHV8’s don’t like a lot of timing like a SBC. They also don’t like a lot of initial timing. On the few stock ones I had, I just set the distributor on the mark and let them run. I recall some guys using a SBC conversion on the 8BA motors, then had to limit advance. I “think” I read this off the Fordbarn. But don’t have direct experience
    My babble aside, can we assume the engine ran properly at one time and is now “fluttering” at higher RPMs?
     
    Truck64 likes this.

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