How many inches of vacuum??
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How many inches of vacuum??

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    Senior Member stallion176's Avatar
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    Default How many inches of vacuum??

    What would be a good number to shoot for on my stealth as far as vacuum? Got a moroso 3 vane setup because under boost I was pushing a little oil out from belt drive. Just want to keep is at a safe level. I was think around 10" but maybe other guys will chime in. I don't want to dry the wrist pins out.

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    Senior Member badbug3's Avatar
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    Quote Originally Posted by stallion176 View Post
    What would be a good number to shoot for on my stealth as far as vacuum? Got a moroso 3 vane setup because under boost I was pushing a little oil out from belt drive. Just want to keep is at a safe level. I was think around 10" but maybe other guys will chime in. I don't want to dry the wrist pins out.

    Twin turbo 605" bbc turns 7200 ish rpms. Lake boat
    i run 6 stage dry sump pumps on all my motors and under boost, with an aluminum block, i feel lucky to break even under boost. Thats about as safe as it gets imo. As long as the engine stays dry im happy and you know its working its ass off to do that.

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    "Need For Speed" Gearhead's Avatar
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    Stallion, on a wet sump oil system 9 to 12 is a good max number. Much more than that and you will begin to cavitate the oil pump. With a three vane running at 1/2 crank speed on a 605" you probably won't achieve that much depression anyway. Going to a few inches of vaccuum from a crankcase pressure situation will be a nice gain on power as well as clean up the blowby on/in the boat.

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    gn7
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    Quote Originally Posted by Gearhead View Post
    Stallion, on a wet sump oil system 9 to 12 is a good max number. Much more than that and you will begin to cavitate the oil pump. With a three vane running at 1/2 crank speed on a 605" you probably won't achieve that much depression anyway. Going to a few inches of vaccuum from a crankcase pressure situation will be a nice gain on power as well as clean up the blowby on/in the boat.
    I agree. That thing would have to be sealed like a submarine to hit much below 10" with that pump, and obviously it isn't, or you wouldn't have posted what you did. You would need a dry sump and possibly Moroso Mondo to get to a number worth worrying about. I believe anything above 12" is reasonably safe for pins and valves. After that you are dealing with things you don't need to be.

    But like Gearhead said, any depression is a benefit, as well as keep the oil in the engine.



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    Senior Member stallion176's Avatar
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    So no need for a relief valve in opposite valve cover? Just bolt in on and run?
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    gn7
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    Quote Originally Posted by stallion176 View Post
    So no need for a relief valve in opposite valve cover? Just bolt in on and run?
    I would get a reading on it. Once you see what pulls, that's about all its ever going to pull. So if you see 8-12", that's about all its ever going to pull.



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    steelcomp was here
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    I'm going to agree with BadBug...I think you'll be lucky to see any vacuum under boost with a TT setup. If you get a few inches, you're golden but you won't know without checking. Under low boost cruise conditions you may get more than you'd guess and I agree on a wet sump engine not set up for vacuum you don't want to run more than 10-12 in.
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    Senior Member Fireguy's Avatar
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    Quote Originally Posted by stallion176 View Post
    So no need for a relief valve in opposite valve cover? Just bolt in on and run?
    I never have on anything that had a power adder. My nitrous SB deal would pull 12-13 max with the 3 vane, until I would detonate it As others have said, put a gauge on it and double check though.

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    Senior Member bp298's Avatar
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    Quote Originally Posted by stallion176 View Post
    What would be a good number to shoot for on my stealth as far as vacuum? Got a moroso 3 vane setup because under boost I was pushing a little oil out from belt drive. Just want to keep is at a safe level. I was think around 10" but maybe other guys will chime in. I don't want to dry the wrist pins out.

    Twin turbo 605" bbc turns 7200 ish rpms. Lake boat
    if you are leaking oil out, it will leak air in. engine has to be tight for a vacuum pump to be effective...

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