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Help stop my headache

  1. #1
    Inland Empire-Big River
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    Question Help stop my headache

    My brain is shot from trying to figure out all the theories, so I'm throwing it to the masses

    I've got a 468 BBC (about 500hp) with about 5-7 hrs on it. Last October and the last day of the season before I was going to bring the boat home I noticed my oil pressure dropping considerably when I was over 4K rpm's. Below 4K the oil pressure would peg itself back over to 70lbs, but as soon as I get above 4k it starts dropping and pretty quickly. The last run out I wanted to see if it would hold together so I let it eat When its cold the pressure stays all the way up (even above 4k rpm's) but as soon as it gets warm it starts dropping again. It dropped enough that I saw the oil psi bounce off 0 lbs It never made any noise and it was riding between 0-5lbs at about 5k rpm's long enough that it should've have been knockin loudly.

    Since October I've been rebuilding the trailer and since thats done now I'm moving on to the motor. I dropped the pan and I can't find one hint of a piece of metal. The only thing I can find is pre-assembly lube. I ran a magnet through it and not so much as a hint of metal was found. I pulled both valve covers and there was plenty of oil up top including what I could see in the lifter valley.

    Number 8 cylinder has a little bit of oil on the plug but nothing that would cause me to think I'm getting a ton of blow by. And I'm not losing any oil and it doesnt smoke at all. At WOT I can get a tiny amount of oil out the breather but again, nothing that would concern me.

    I have a 10 qt. milodon pan with melling HV pump. Pan has windage tray and trap doors so I dont think the pump is having a hard time finding oil. I spoke to milodon about my pickup and they say I should have the high performance one instead of the one I have now. They said my current pickup is not that great over 4500 rpm's, but I can't seem to understand how my pickup would be the problem.

    Recap: When its cold the oil pressure virtually never moves no matter what rpm. When its warm the oil pressure starts dropping above 4k but as soon as I let up a little the oil pressure jumps right back up. No metal found but my head hurts

    Thanks in advance for the help!

    Richard

    We wash our parts in gasoline,
    We drink Alcohol,
    And we go racing with Nitro-Methane!

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  3. #2
    Senior Member Cat Sass's Avatar
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    I have had the same problem in the past. questions- so we can compare notes:

    Is your block filled? (water jackets)
    Do you have an oil cooler?
    Electric or mechanical oil pressure guage?
    What is your compression ratio?
    What fuel do you run?
    What is the engine temp when this happens?
    Roller or flat tappet cam?


    I beat my head against the wall for years over the same problem, And finally built another engine. The first one never let go though.

  4. #3
    Inland Empire-Big River
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    Quote Originally Posted by Cat Sass View Post
    I have had the same problem in the past. questions- so we can compare notes:

    Is your block filled? (water jackets)
    Do you have an oil cooler?
    Electric or mechanical oil pressure guage?
    What is your compression ratio?
    What fuel do you run?
    What is the engine temp when this happens?
    Roller or flat tappet cam?


    I beat my head against the wall for years over the same problem, And finally built another engine. The first one never let go though.

    It has water jackets
    No oil cooler
    Electric oil pressure gauge (I know...I'm thinking going mechanical)
    10:1 compression
    91 octane
    approx. 150-160 degrees
    Flat tappet (not good with todays oil)

    We wash our parts in gasoline,
    We drink Alcohol,
    And we go racing with Nitro-Methane!

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  6. #4
    No Sandbar To Far sanger rat's Avatar
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    Upgrade to the Mellings Select oil pump. The regular HV aren't as good as they once were.
    Quote Originally Posted by One More Year View Post
    The only blab's I will even be a part of is just when it is me they are talking about. Aaaah yes I can see a few good looking shiny tall deck motors on the beach, with barely enough fuel to get back to the launch saying, "Holy crap how fast you think that Daytona was going man? That's like the 20th time he's gone by today?"

  7. #5
    Inland Empire-Big River
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    Quote Originally Posted by sanger rat View Post
    Upgrade to the Mellings Select oil pump. The regular HV aren't as good as they once were.

    The one that I have on there now is the Melling M77HV (which they say pumps 25% more than stock) I'll look into that though.

    We wash our parts in gasoline,
    We drink Alcohol,
    And we go racing with Nitro-Methane!

  8. #6
    Cantard 71hallett's Avatar
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    Have you measured from the pick up to the bottom of the pan? Hot oil flows easier and if your pump cavitates.....

  9. #7
    E-7 Sheepdog (ret) SmokinLowriderSS's Avatar
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    How overfull is the oil pan?
    "As democracy is perfected, the office of president represents, more and more closely, the inner soul of the people. On some great and glorious day the plain folks of the land will reach their heart's desire at last and the White House will be adorned by a downright moron."
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    The rest of us are being dragged along kicking and screaming.

  10. #8
    Senior Member Cat Sass's Avatar
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    Quote Originally Posted by rivrrts429 View Post
    It has water jackets
    No oil cooler
    Electric oil pressure gauge (I know...I'm thinking going mechanical)
    10:1 compression
    91 octane
    approx. 150-160 degrees
    Flat tappet (not good with todays oil)
    OK, I always thought it was either oil temp related, or detonation related, when I had the prob.

    The first thing I would do is add a mechanical oil pressure guage. Keep the electric one, and compare the two. Heat increases resistance in the oil pressure sender, which in turn changes the reading on the guage. Also, on the mechanical guage, keep the connection either short, or large. Use a -4 hose to feed the guage. Cold oil in a small tube makes the guage respond very slowly.

    Next, a cool motor tends to resist detonation, It could be detonating when it gets warmer under long wot conditions. Try retarding the timing a few degrees. If that doesnt help, richen the fuel mixture a bit. If this is the boat in your avatar, air scoops tend to lean out the fuel mixture at speed. Maybe result of detonation from higher atmospheric pressure inside the scoop at speed.

    Other possibilities are areated oil, possibly caused from too much oil in the pan. Or maybe not enough oil. Try adding oil first, then taking some out. I know it sounds crazy, but too much oil can cause the crank and rods to splash into the oil and induce air into it, the air cavitates the oil pump.

    Dont forget that plain old oil temperature could be the problem. If its up around 240 or so, its not gonna work right.

    I got more.........give me some feedback

  11. #9
    No Sandbar To Far sanger rat's Avatar
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    Quote Originally Posted by rivrrts429 View Post
    The one that I have on there now is the Melling M77HV (which they say pumps 25% more than stock) I'll look into that though.
    The 10778C is the one to use. http://www.jegs.com/i/Melling/689/10...751586%7C10453
    Quote Originally Posted by One More Year View Post
    The only blab's I will even be a part of is just when it is me they are talking about. Aaaah yes I can see a few good looking shiny tall deck motors on the beach, with barely enough fuel to get back to the launch saying, "Holy crap how fast you think that Daytona was going man? That's like the 20th time he's gone by today?"

  12. #10
    Inland Empire-Big River
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    Quote Originally Posted by 71hallett View Post
    Have you measured from the pick up to the bottom of the pan? Hot oil flows easier and if your pump cavitates.....
    Hallet - thats the first/easiest thing I did but its within 3/8" from the pan. It hasn't done this all along either. Thanks for the heads up

    We wash our parts in gasoline,
    We drink Alcohol,
    And we go racing with Nitro-Methane!

  13. #11
    Inland Empire-Big River
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    Quote Originally Posted by Cat Sass View Post
    OK, I always thought it was either oil temp related, or detonation related, when I had the prob.

    The first thing I would do is add a mechanical oil pressure guage. Keep the electric one, and compare the two. Heat increases resistance in the oil pressure sender, which in turn changes the reading on the guage. Also, on the mechanical guage, keep the connection either short, or large. Use a -4 hose to feed the guage. Cold oil in a small tube makes the guage respond very slowly.

    Next, a cool motor tends to resist detonation, It could be detonating when it gets warmer under long wot conditions. Try retarding the timing a few degrees. If that doesnt help, richen the fuel mixture a bit. If this is the boat in your avatar, air scoops tend to lean out the fuel mixture at speed. Maybe result of detonation from higher atmospheric pressure inside the scoop at speed.

    Other possibilities are areated oil, possibly caused from too much oil in the pan. Or maybe not enough oil. Try adding oil first, then taking some out. I know it sounds crazy, but too much oil can cause the crank and rods to splash into the oil and induce air into it, the air cavitates the oil pump.

    Dont forget that plain old oil temperature could be the problem. If its up around 240 or so, its not gonna work right.

    I got more.........give me some feedback
    Ya, its the boat in my avatar

    I guess I'm not crazy I think I have been thinking along the same lines. When I brought it home I ran it on the hose with little issues (oil pressure stayed fine). I started with 10 qts and dropped to almost 7 qts but like I said little difference took place while it was on the hose. I'm gonna start with 7 qts. and work up to 9 or 10 but while its under load at the river. I'm gonna see if it makes a difference. I typically run 8 qts in the 10 qt pan. Then I'll move to timing and then to air/fuel mixture. Awesome advice. Its gonna have to be a process of elimination. Its just a cringing feeling to see the gauge drop and leave your foot in it

    If it was gonna eat itself it already would've done so if the gauge is accurate.

    I think I'm gonna grab a mechanical gauge this weekend and see what happens. If nothing else it was an excuse to replace mediocre gaskets with the best

    Thanks for the heads up Cat Sass & Sanger Rat. I'll let you know what happens.
    Richard

    We wash our parts in gasoline,
    We drink Alcohol,
    And we go racing with Nitro-Methane!

  14. #12
    Resident Ford Nut Sleeper CP's Avatar
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    As stated make sure of your clearance from the pan to pick up. You may want to drop two quarts of oil to see what happens.

    Lastley, You may want to try a blueprinted standard volume oil pump. The HV ones eat HP (just a little) but they also pump more oil than you really need. Your boat engine running long distances at 3,500 plus is not like a car or truck that uses the HV pump.

    Edit : I just read your last post.... sorry for the duplication. The mech guage is a good idea.

    Just my .02

    Sleeper CP

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    fast is the other half.
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  15. #13
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    I agree with Sanger Rat..Mellings even admits they are having problems with the 77 and 77HV's. I got the Select and its been much better.

  16. #14
    Cantard 71hallett's Avatar
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    Quote Originally Posted by Blue View Post
    I agree with Sanger Rat..Mellings even admits they are having problems with the 77 and 77HV's. I got the Select and its been much better.
    Not to hijack but what problems are they having?

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