Pinging at high RPM

Discussion in 'Street/strip 400/430/455' started by matt68gs400, Jun 21, 2016.

  1. 8ad-f85

    8ad-f85 Well-Known Member

    What is your existing plug telling you?
     
  2. matt68gs400

    matt68gs400 Well-Known Member

    Charts say to use a r44TS. I was wrong, they still have 44s. Auto store came up with a 45. I'm going to try a 43, a cooler plug than my 44s.

    One hour later, new plugs purchased and installed. Engine runs smoother but haven't tried high RPMs; starting to rain.

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    Last edited: Jun 22, 2016
  3. Gary Farmer

    Gary Farmer "The Paradigm Shifter"

    Remember here too that at higher RPMs VE will increase cylinder fill and increase effective compression vs where it would be at lower RPMs. If your engine is borderline safe on the octane you're using, it could begin pinging at higher RPMs as the cylinder fill increases.

    That's my initial gut reaction anyway. Then I read down where your cam's ICL is 60*, which is waaaay earlier than the stock cam's (even if this aftermarket cam was installed with a lot of retard) and the picture begins to clear up even more.

    Best wishes,


    Gary
     
  4. Gary Farmer

    Gary Farmer "The Paradigm Shifter"


    With Buick's big block combustion chamber size and super wide bore, more leeway is needed for DCR to reduce detonation vs smaller sizes and narrower bores, unless you get the proper quench.

    This means that even at 7.88 DCR, it would be in 'race gas' territory without quench. Generally speaking.


    Gary
     
  5. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    No problem, I value your input always. Have a couple of club members who stripped threads in aluminum heads so I take the safe route:grin:
     
  6. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Yes, my DCR is 7.84 but I have a 0 deck motor with aluminum heads. It runs happily on 93, but I still mix in a little race gas at the track for extra insurance when I am wide open through all 3 gears for that long.
     
  7. 8ad-f85

    8ad-f85 Well-Known Member

    Regarding the plug, I was asking about the heat and timing indications on it, not the chart.
    There's many times you have to deviate from the book's starting point.
    The first couple of threads from the chamber should be dry looking.
    You might have to do more Google searching on that.
    There's a lot of valid and sometimes conflicting info, but it can all help to steer you.
     
  8. 300sbb_overkill

    300sbb_overkill WWG1WGA. MAGA

    Which is much harder to do with stock or stock type pistons with a full diameter dish. With most BBBs, quench is basically non-existent unless aftermarket pistons with an actual quench pad on them are used.


    Derek
     
  9. matt68gs400

    matt68gs400 Well-Known Member

    Great information here guys. Thank you very much! I'll have to check Compression, but it'll be a while for that now. Did change plugs, here's a pic of the new vs. the old. I don't recall changing them last year, not sure how much they were used. Took the car out again, as the rain never happened, still no pinging below 4200 RPM, that's as high as I got tonight. Found a Sunoco station that has 93 octane but it has 10% ethanol in it so I went with 91 octane and no ethanol.

    [​IMG]

    And with camera flash on:
    [​IMG]


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    Last edited: Jun 25, 2016
  10. 8ad-f85

    8ad-f85 Well-Known Member

    Cool, you'll have to look at the business end closer.
    Get your Google ready and learn some old school things
     
  11. matt68gs400

    matt68gs400 Well-Known Member

    I'm no expert on plug analysis. I'll have to do some research.

    One hot rodder thought it looked like high speed glazing, which causes misfire at higher speeds. The suggestion for that is to replace the plugs and consider using a colder plug.

    [​IMG]
    [​IMG]


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    Last edited: Jun 23, 2016
  12. 8ad-f85

    8ad-f85 Well-Known Member

  13. matt68gs400

    matt68gs400 Well-Known Member

    Thanks, I skimmed it quick, will have to read in depth later. One thing that stood out to me is the color change of the ground strap. In the article it says it's an indicator of too much timing. This was a problem for me with the old distributor, but that has been replaced now, so that's one thing fixed.


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  14. 8ad-f85

    8ad-f85 Well-Known Member

    Cool.
    The issue of a distributor or timing isn't necessarily one that is "fixed", it's still subjective.
    If it's pinging @ 30* timing, there's signs of other issues.
    Dampner mark could be off or any of the previously mentioned things.
     
  15. matt68gs400

    matt68gs400 Well-Known Member

    Yep, makes sense. It could have been a combo of just old plugs that were a bit glazed and too much timing in the past.

    Timing is likely fixed. Plugs are new and cooler. I'll keep an ear on that motor and see how things go. Lots of good information. I really appreciate everyone's help on this.

    I'll be checking the secondary metering rods soon just to see if that might be contributing to a lean mixture as well.


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  16. matt68gs400

    matt68gs400 Well-Known Member

    My secondaries have CD stamped on them. I think that's 0.057, listed as having a long power tip with full enrichment at 70 degrees valve opening.

    http://quadrajetparts.com/mobile/qu...0-diameter-mp-163.html?redirectCancelled=true

    [​IMG]


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    Last edited: Jun 24, 2016
  17. Gary Farmer

    Gary Farmer "The Paradigm Shifter"

    Indeed sir. The Buick 350 is a bit more forgiving on this with its open chamber design because of the narrow bore and smaller combustion chamber, though in the OP's case with his big block, the smaller cam's earlier intake valve closing point is in all likelihood the culprit behind this higher RPM detonation using 'stock' style combustion chambers/pistons.

    Without having to do some major surgery to the engine, the real way to fix this is to do as others here have already suggested, and that is to run premium pump on the street for 'normal' driving and put in some higher octane race fuel for any racing, OR put in a larger cam with later valve events (without having to dig into the bottom end).

    You guys wouldn't believe me if I told you the bone stock OEM's .006 closing event. I had trouble believing it myself at first, but after careful study (and cases such as this) I understand why it's so late. The Buick big block is a totally different beast than the 350 (and even other, smaller bore big blocks).

    With the idea originating as a 400 CID engine, and then later inflating to 430 for use in larger, heavier cars, and then even further to 455 CID, and even THEN to larger valves, tighter springs, and larger cam (for the Stage1 455), all using similar airflow designs (and exhaust manifolds), the OEM camshaft had to be very accommodating on the larger displacement variants (all of which used a larger bore to achieve the additional displacement--which exacerbated the detonation issue). Change it without modifying the other parts, and you just created a monster (both good and bad). Without fully understanding what's going on inside the engine's science and engineering, it's very easy to run into unforeseen problems.

    Change another part to help with the one you just changed before, and it may 'fix' it (or seem to at first), and then bam, another issue or issues arise now compounded with multiple changes instead of just one. Sometimes we get lucky, sometimes not. Best to iron it all out before the bolts are tightened on that final assembly. This is where research, experience, collaboration, and some theory tossed in for good measure can pay off. We're all in this together. Best if we can help each other best we can with what we know how to do so that everyone can benefit, not just a few or the ones with the most money. :TU:

    EDIT: Though I'm not 100% satisfied with this post's assertions (because there are some assumptions made by me about the OP's engine based on limited information, and could very well turn out to be wrong), it's still useful in a 'generally speaking' sense.


    Gary
     
  18. gmcgruther

    gmcgruther Well-Known Member

    Here is something to think about, I was reading David Vizards books and he is legendary for getting massive torque out SBC ,same as HP or above on all his sbc's. LCA is his trick. He goes on talking about DCR, you only aacount DCR on a fully sealed engine, (ProStock Engine ring sealing) . Take cylinder pressure reading in PSI, make sure you crank engine over atleast 3-5 times. This is very accurate on DCR then. Unplug your coil first though. If the DRC on you engine is suppose to be 7.83:1 then the psi should match.
     
  19. matt68gs400

    matt68gs400 Well-Known Member

    Larry, who are Mark and Ken?


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  20. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

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