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Thread: Help me with a couple of issues please

  1. 11-09-2011 #1
    98hc4mula
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    Help me with a couple of issues please

    first and foremost....thank you all who have helped me go through this and helping me get the tune where it is at...it is getting where I want it but have come across some issues.

    on the log during WOT the MAP goes a little crazy. It fluctuates up and down like drawing a vacuum. I dont know why this is. there is no vacuum leaks and it pulls strong as far as I can tell. what could cause this? the heads are 205 AFRs on a 408 with 92/92 TB.

    also im seeing KR at above 6000 rpms a total of 4 degrees is seen, cant figure out why its doing this with the timing set at 22 at wot areas.

    please look at the logs and help me sort this out. I am at my wits end.

    It was suggested that the springs may be floating and causing this KR to occur. they are good for .650 lift. I had a shop go through the heads recently due to my engine failure on cyl 5 and 7.

    ask anything you need to know about the car to figure this out....I thank you in advance
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  2. 11-09-2011 #2
    tramotorsports
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    Springs are good to .650" What size cam is in the car? Can't imagine you're are getting valve float if all is good but it is possible. May also be getting false knock?

    The MAP reading suggest that your intake is just not big enough. If the plenum volume is too small the engine draws a vacuum on it because there is no more atmospheric pressure air for the engine to suck in.
    AAHHHHH!!!!!!
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  3. 11-09-2011 #3
    tramotorsports
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    If you increase the timing does the knock retard increase or stay at 4?
    AAHHHHH!!!!!!
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  4. 11-09-2011 #4
    98hc4mula
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    Havent tried running it at different timing. Will try that this afternoon. Also I have stock 78mm maf there.
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  5. 11-09-2011 #5
    mecanicman
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    I agree map reading will draw into a vacum with the intake being to small. However I have never seen one dance like that. On the big cube motors I have expieriance with at a certain rpm you see the map start to fall, but not dance. I had a 440 engine that last year had a 92 on it, did exactly what I described but log shows a smooth transition. This summer a 102 was installed, it still pulls a vacum but at a higher rpm and smooth transition. I would find the fluctuations troublesome, especially with your previous failure, but I dont know where to point you.
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  6. 11-09-2011 #6
    98hc4mula
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    I may have a lifter that is not pumping up....today the engine had a tic on cold start up that got a lot better upon warm up.

    geeeezzzzzz I cant seem to get a break with this bad girl
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  7. 11-09-2011 #7
    98hc4mula
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    funny thing is that it does not do it all the time. I turned it on today twice and only did it on first start up.
    wow...my luck
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