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  1. #46
    Senior Member LXCHEV's Avatar
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    That information on 'crevice volume' makes a lot of logical sense. Having read that formal explanation now, I think it really goes a long way to explaining what many of us are seeing in our engines. Even if it's just one contributing factor.

    I was actually chatting to someone about this earlier this week (whose opinion I highly value in the industry as he's spent a lifetime building and tuning performance engines) - and he commented that it's not uncommon at all and that there are just certain things that happen, particularly in these old school cammed carby engines that can't always be easily explained or resolved. He even mentioned how they've researched intake charge using clear plenums and have observed unusual fuel pooling and all sorts of things like that. There are so many variables involved from carb settings and signal strength, through to the intake, cam specs, chamber design, timing etc etc... fascinating topic though. Would love to have the ability to record video footage from inside the chamber - why can't someone invent that?! Perhaps a special spark plug that doubles as a fire-proof 360 degree camera...

  2. #47
    Senior Member LXCHEV's Avatar
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    I've just put some updates on where I'm at with my old dinosaur here: https://www.aussiev8.com.au/showthre...-383-SBC/page4

    Finally did a leakdown test - 7%, 8%, 9%- certainly nothing to be upset about there for an older engine.

    I've removed my PCV and I believe I now have my carb settings as close to perfect as they're ever likely to be. Still on the fat side though, there's always room for improvement.
    My dyno tuner has also given his nod of approval for the 'business end' of my spark plugs - they're doing all the right things.

    Yet to go any further with the vac advance dizzy swap, but I do still intend to go down this road.

    For now - I'm fairly convinced my oily/fuelie threads come down to this crevice region/volume. I'll be keen to see if they do clean up a bit more now though after my recent changes. Will report back in due course.

  3. #48
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    hi
    I have had 10% leakdown loss where cross hatch was partly missing , stripped the engine and measured bores and all were 3/4 or above , worn out .
    But remember leakdown testers are only really accurate when compared against there own readings . Trying to compare one brand to another is not a great idea , best used as an indication .

  4. #49
    Senior Member LXCHEV's Avatar
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    Yep agree completely swampy. Eric at Goody's who did my leakdown test, does them a lot for a variety of his customers - especially race cars where leakdowns will be done at least annually, purely to monitor engine health. The fact he was really happy with my results, tells me that with his equipment and readings, I'm in the green. I'll continue to do my own comp tests once a year and hopefully see many more years of reliability from this engine.

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