weird oil pressure issue on a 4 bolt block
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weird oil pressure issue on a 4 bolt block

  1. #1
    mo balls than $cents$ IMPATIENT 1's Avatar
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    Default weird oil pressure issue on a 4 bolt block

    my uncle put together a 13 to 1 468 for 1 of our buddies and when your in the water idling it has 60psi and as you step into the throttle, the pressure steadily goes to shit, let off the throttle, pressure builds right back up to 60psi. it has a 10qt trap pan that's in great shape, new oil pump and the pick up is about 1/4in off the floor of the pan, runnin a full 10qts of oil in it. this same block ate a rotating assembly up prior to my uncle's overhaul job and now it has us both wonder if the block is flexing and opening up a crack in the galleries. someone converted the block into a splayed 4 bolt, started out its life as a high nickle 2 bolt. any chance some cracked the block when they did the 4 bolt conversion? i've never seen such a thing, has me puzzled. makes sense that the last crank got smoked at wot, cause as long as you're holding the go pedal down, the oil pressure continues to dive we didn't hurt anything testing it saturday, noticed the issue right away and put it back on the trailer. clearences were as perfect as perfect gets, has new cam bearings, its non restricted at the cam gallery, fully roller motor.

    what would make the oil pressure dive where it'd normally climb with throttle? there's no bearings bad, its already back on the stand, just not see'n anything wrong anywhere other than the block has been tampered with at 1 time.oil pressure bypass in the filter adapter is blocked as well.mark 4 block
    Last edited by IMPATIENT 1; 08-03-2009 at 02:36 PM.

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    Super Moderator HammerDown's Avatar
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    Some 10 qt pans like my Milodon Jet pan seem to do better with 8 qt's in the pan...> less chance of the oil getting to the crank and foaming it.
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    Quote Originally Posted by HammerDown View Post
    Some 10 qt pans like my Milodon Jet pan seem to do better with 8 qt's in the pan...> less chance of the oil getting to the crank and foaming it.
    tried lowering the level, increasing it and it had no effect. its something super abnormal cause i wouldn't have believed it if i hadn't been sitting in the boat watching the gauge. at idle it has 60psi, you bring it up to 3krpms, and the pressure will just start goin down and down until you let outta the throttle and then it'll start to climb back up just as fast as it went down. weirddddd

    it does have a different pump and fresh pick up from the last time it smoked a crank. they thought he was pulling wheelies and letting the pickup go dry, but after the motor got put together with all new stuff, the oil pressure issue had to be the reason it smoked the 1st crank and bearings.

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    We had a motor that did the same thing last year. We put it on the dyno and bringing up the RPM's it did the same thing. We tried everything. More oil, less oil, different filters, restrictors, different weight oils and so on. We finally tore the engine down (it looked great) and rebuilt it with a different oil pump but reused the pan and pickup (since it was a special v-drive pan) and it did the same dang thing. We tore it apart again and checked everything. Out of frustration I took one of my personal oil pans off of one of my engines and put it on the dang thing. Perfect! The oil pressure was spot on. I figure the issue probably had something to do with the pickup, but I did not care to really inspect it. Instead I took the pan and pickup to the side of the shop and had some fun with a 10 Lb. sledge hammer. I felt better afterwords.

    Paul

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    what brand of filter,and did you try changing it before you pulled the motor?
    what weight oil?
    are you running a filter mount bypass or is it blocked off?
    v-drive or jet?
    i would pull the pump and run a oil pump dyno test on it to check for bypass pressure problem and make sure oil pickup is welded to the pump.
    do you have a windage tray on it?

    if it's a milodon oil pan throw it away.and get a stefs or dooley pan you will be money a head.
    how about some pics when you get the pan off...

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    gn7
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    We went thru every conceivable oil pressure problem I know of a back in 2004. And I learned a ton about wet sumps thru it all. 1/4"off the bottom is fine, rather have 3/8", but I assure you that is not your problem. If it is a Milodon pan and pick up, can the pick up. They are crap. I think the problem lies in the fact that they use a perferated plate instead of screen. The Milodon pans get blamed for a lot of problems that are really the pick up. The pickups are junk, period! The pans are not the best marine piece, but they work better than you describe. The pick up CANNOT be round unless it has a baffle like a stocker has. A round pick up will start a vortex without some sort baffle under it. The pickup HAS TO BE FLAT and Parallel to the bottom of the pan! But the most important, check for a crack between the pickup box and where it goes in to the pump. Inspect the hell out it, then cover the pickup box with your hand and blow into the tube. Good luck, let us know what you find.



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    Last edited by gn7; 08-03-2009 at 03:19 PM.

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    Senior Member Widetrack's Avatar
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    Tom, A friend had this same problem under acc. it would fall! Toasted two 468s it ended up being the bottom of the pan was so close to the bottom of the boat and under hard throttle boat flexed into pan closed off pickup!
    And sometimes converting 2 bolts to 4 bolts can run into problems with the blocks casting! WT


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    gn7
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    Never heard of a boat bottom flexing enough to move the bottom of the pan to the point of shutting off the oil flow. I'd get rid of the boat Have had the pan bottom get sucked up by the pickup. That's the reason Dooley's are waffled on the bottom, to strengthen it, and why my pickups have stand offs welded to the pickup so if the pan bottom does come up, the stand offs keep it from blocking the pickup. The Mellings alumn billet pump has little standoffs built into it bottom of it.
    http://www.summitracing.com/parts/ME...S/?image=large



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    Last edited by gn7; 08-03-2009 at 05:25 PM.

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    scott had this problem a few years back with his race boat mill,ended up having a crack in the block,losing oil pressurehope this is not your problem.good luck tom

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    i'll take a hard look at the pick up, at a glance i didn't see anything wrong with it.he already told the friend to find another block to drop this stuff into

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    Quote Originally Posted by gn7 View Post
    Never heard of a boat bottom flexing enough to move the bottom of the pan to the point of shutting off the oil flow. I'd get rid of the boat Have had the pan bottom get sucked up by the pickup. That's the reason Dooley's are waffled on the bottom, to strengthen it, and why my pickups have stand offs welded to the pickup so if the pan bottom does come up, the stand offs keep it from blocking the pickup. The Mellings alumn billet pump has little standoffs built into it bottom of it.
    http://www.summitracing.com/parts/ME...S/?image=large
    He did! Boat,pan,pick-up, and block(s)! Setup was way to close to bottom of boat!


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    after reading some other similar threads, i think we should try a new pan set-up before condeming this block just yet. its the cheapest thing to do anyways.

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    Senior Member CK7684's Avatar
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    Sounds just like my problem...I'm awaiting a Stephs pan now, so I dont have any results yet...

    Curious, what pan are you running now?
    Last edited by CK7684; 08-04-2009 at 01:03 PM.

  16. #14
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    Quote Originally Posted by CK7684 View Post
    Sounds just like my problem...I'm awaiting a Stephs pan now, so I dont have any results yet...

    Curious, what pan are you running now?
    not really sure, but we're having great luck with a hamburger pan on my uncle's tt496, and since they're cheap to buy, we'll get the owner to get 1 on the way tonite.

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