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Technical Engine guys what do you see

Discussion in 'The Hokey Ass Message Board' started by mcmopar, Aug 2, 2021.

  1. Paul
    Joined: Aug 29, 2002
    Posts: 16,525


    I'm unfamiliar with the 340, is it normal to have the plugs reach so far into the chamber? Looks like 3-4 threads in the fire.
    Is that carbon tracking on the porcelain?
    And the gap seams quite large.
    loudbang likes this.
  2. RodStRace
    Joined: Dec 7, 2007
    Posts: 4,651


    EDIT, just saw Paul's post. Yes, that is a typical 'long reach' plug for a SBM, the threads tend to get discolored like that, but they only extend the unthreaded portion when installed. I didn't find a picture quickly, but look at the thumbnail for this video
    I agree with him on the gap. MSD can provide more spark energy than stock (actually more sparks, hence the name), but you said
    In most cases where the mixture is at a higher pressure before ignition (high compession, blower or turbo), you want a smaller gap, not bigger.
    Last edited: Aug 8, 2021
  3. mcmopar
    Joined: Nov 12, 2012
    Posts: 1,737

    from Strum, wi

    I shimmed the rockers for side to side movement, now set at .019. I installed a new valve, took oil pan off to look for valve tip only to find small pieces. I believe it was a soft tip on the valve.

    I went back just to make sure and the MSD sheets say .050 to .060 on motors up to 11 to 1 compression. it says to go smaller like you mention when turbo or blower or higher compression.

    Paul and RodStRace like this.
  4. Tutashen
    Joined: Aug 8, 2015
    Posts: 86


    Your plugs imho show to much timing and i like what can be seen of the porting on the heads it looks like your oiling around the intakes and from the pics the shrouding on the intakes is way off there is no doubt your having flame issues and the cylinders aren't firing the same, i would get out the grinder an have another look at the guides while your at it, was to much meat taken off around the guides to seal ? o well my 2 cents and nothing beats putzing around with motors :)
  5. choptop40
    Joined: Dec 23, 2009
    Posts: 5,409


    these problems are head-aches.......
  6. noboD
    Joined: Jan 29, 2004
    Posts: 8,529


    So I never read where did the valve head turn up? It's too big to go threw the exhaust valve unless it broke apart. But the piston doesn't look bad. It could be hiding in the intake manifold.
  7. noboD
    Joined: Jan 29, 2004
    Posts: 8,529


    I think it says when he took it apart the top of the valve is missing. Maybe I missed something.
  8. The valve lost the tip of the stem, not the head. Hopefully Tony has this all figured out.
  9. Not to hijack the OP's thread, but why is this?

    I'm just learning about reading plugs for timing. Feels like I should have been taught this in trade school 25 years ago.

    My understanding is you want the transition from light to dark on the electrode to be about in the middle of the curve, correct?
  10. I see, "Buy a factory crate engine", put it in and get on down the road.

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