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Low oil pressure from 351M

Discussion in 'The Hokey Ass Message Board' started by 56KUSTOM, Jun 30, 2012.

  1. I have used an electric gauge and a mechanical one and they both start at 60lbs cold and drop to 10lbs warm.I bought the car with no info on the engine hoping for the best.It doesn't make noise or smoke.The oil looks pretty dirty when I drained it .What is the best oil and/or additive to help the pressure?
    I bought a high volume pump but really don't wanna get into it right now.I've been trying to get it inspection worthy to have some fun this season.
     
  2. Wensum Valley Rods
    Joined: Oct 13, 2008
    Posts: 287

    Wensum Valley Rods
    Member
    from England

    I have a 351m in my truck, it reads 65lbs at idle from cold and drops to 20ish when warm. If I drive it hard for a while then it struggles to show much pressure at al on idle. It always shows between 25-40 when cruising and warmed up.
    Its been this way for the last 3 years and is a daily driver. Never shown any problems. I did read on here somewhere that these engines have low oil pressure when warmed up.
    Hope this helps.
    Paul.
     
  3. George
    Joined: Jan 1, 2005
    Posts: 7,283

    George
    Member

    Is that idling under 1K with 10 lbs or running down the road?
     

  4. What weight of oil is in it (if known)? Also, what brand of pil filter?
     
  5. TrioxinKustoms
    Joined: Oct 16, 2009
    Posts: 551

    TrioxinKustoms
    Member
    from Romney, WV

    they just have shitty oil pressure.. same as the 400s.
     
  6. Mule Farmer
    Joined: Jun 1, 2005
    Posts: 1,508

    Mule Farmer
    Member
    from Holland MI

    351m and 400m have low oil pressure because there shit, they always have been!!!!!!!!!!!!!!!!!! That's why they throw the rods out of the bottom of the pan. I'm a big ford man and I have had a lot of the Ms, and they are all the same, rod knocking, gas pigs, that make no power.
     
  7. tommyd
    Joined: Dec 10, 2010
    Posts: 11,330

    tommyd
    Member
    from South Indy

    :DThat made me laugh! But it's also true.
     
  8. Don't know what was in it for oil and they painted over the filter when they painted the engine.
     
  9. Maybe 12 or 13 running down the road.
     
  10. George
    Joined: Jan 1, 2005
    Posts: 7,283

    George
    Member

    Try 20W-50 & a Wix 51515
     
  11. George
    Joined: Jan 1, 2005
    Posts: 7,283

    George
    Member

    That's not good....might be time to check clearances..
     
  12. junkyardjeff
    Joined: Jul 23, 2005
    Posts: 7,531

    junkyardjeff
    Member

    If those motors are not well cared for the oil pressure will get low.
     
  13. This. Use a Napa Gold (Wix), or a Baldwin, or a Motorcraft, if the Wix isn't available.

    Beyond that, it's probably time to pull the pan and have a look.

    So far as the 351Ms being shit- I would agree with that, in stock form...though they seem to run forever in spite of factory-installed preignition...but a 400 or converted 351M if built properly can be a fantastic street engine in the right application.
     
  14. Mule Farmer
    Joined: Jun 1, 2005
    Posts: 1,508

    Mule Farmer
    Member
    from Holland MI

    Soon enough you'll be able to look through the hole in the pan to see what the clearances are like.

    They are good for about 120000 or 130000 thats about it.


     
  15. Dave50
    Joined: Mar 7, 2010
    Posts: 1,751

    Dave50
    Member

    Bearings are wiped common on them. Has it had any work done recently head gaskets intake?
     
  16. Dunno anything but what I can see and hear.I would like to get it so I can have a little fun this year before tearing apart or hunting for a cleveland. You would think whoever started this project would have put a rebuilt in!
     
    Last edited: Jun 30, 2012
  17. monkeyspunk79
    Joined: Jan 2, 2011
    Posts: 553

    monkeyspunk79
    Member

    Maybe.

    If they're taken care of they're fine...and will last much longer than that. Had a 351M in an old Ford truck that pulled a 35 foot camper from St. Louis to Yuma every year since 1978. Hauled coal and firewood in the winter and was driven hard, but maintained. It sat for 10 years after the flood of 93 took out the truck. I got it going again, and drove the snot out of it. After two years of abuse, the 351M had 207K on it before the bearings finally went like the OP was describing with low oil pressure. I threw a 400 in there and kept on truckin'. Can't beat the torque of those motors with an RV cam and good intake & exhaust. They get a bad rap because people think they're a big block that you can wind like a small block. That ain't the case...you'll roast the bearings.

    Anyhoo....The recommendation for 20W50 and a good filter is right on. It will get you some more life out of it until you save up for a transplant or rebuild kit. If you choose to rebuild it, throw some good bearings in there and don't go crazy with the bore. The cylinder walls are thin on those engines. Good luck with it.
     
  18. Thanks guys for all the help!Tomorrow I'm gonna try the oil and filter and see how it goes.
     
  19. junkyardjeff
    Joined: Jul 23, 2005
    Posts: 7,531

    junkyardjeff
    Member

    I had a 351-M in a 78 f150 that was bought new by my dads buddy that had almost 200,000 on it when I sold it and still had great oil pressure,it had a RV cam and would pull about anything and could not feel it plus got it got decent gas mileage.
     
  20. Insane 1
    Joined: Feb 13, 2005
    Posts: 973

    Insane 1
    Member
    from Ennis TX

    Lots of guys building 400's now cause they have tons of torq. Owned one that was so woreout that when the lifters started ratteling you knew to put oil in it, but there was no way to kill it.

    Get a bad rap because of the smog shit after 72, but 71 is the year to get as there were internal changes after 72...take a look around and see what some guys are doing with them........

    But as for oil pressure I have a 68 Galaxie wa 390 that idols at about 8-10 psi...drive it everyday and been that way for over 10 years since I bought it......
     
  21. On the Ford forums some guys were saying that the top rear location of the sender gives a lower reading than if it was near the oil filter.Any thoughts?
     
  22. junkyardjeff
    Joined: Jul 23, 2005
    Posts: 7,531

    junkyardjeff
    Member

    There probably is some truth to it since its up near the rear cam bearing.
     
  23. monkeyspunk79
    Joined: Jan 2, 2011
    Posts: 553

    monkeyspunk79
    Member

    Yes, I remember a popular mod for Ford trucks & Broncos of that vintage with an M motor was to install a fitting near the oil filter for a 'true' reading. Forgot until you mentioned this. Worth a shot and only costs a few $ in brass fittings.

     
  24. Well,I changed the oil and filter and put in 20w50 and I now have 75lbs at start and 25 after a good run.I guess I can live with that.
     
  25. monkeyspunk79
    Joined: Jan 2, 2011
    Posts: 553

    monkeyspunk79
    Member

    Sounds good to me. As long as those lifters aren't making noise, run it! :)
     
  26. Engine man
    Joined: Jan 30, 2011
    Posts: 3,476

    Engine man
    Member
    from Wisconsin

    Actually, it's better to know what it is at the rear because that's the pressure that the bearings are getting. Somebody might have used 5w-20 oil in it or the oil was in it for too long.
     
  27. Any way to tell what brand the old filter was, by scraping off paint or whatnot?
     
  28. This could be your classic "Band-Aid on an amputation".

    If the engine is not for racing, it shouldn't be using racing oil.

    With what I've read you probably already have bearing damage.

    If the 351 you are using is from 1977 to I believe it's 1980, those engines had oil pump problems right from the factory.

    Well Look at the bright side! You already have the new oil pump. Now you just need to buy all the other parts it's going to take to rebuild your engine. ;)
     
  29. trollst
    Joined: Jan 27, 2012
    Posts: 1,781

    trollst
    ALLIANCE MEMBER

    Actually, I would have agreed these engines are crap, having wiped one out myself, BUT, I discovered, they have huge mains in them, you gotta keep the oil clean and changed to make them live. Then, change the cam, add an aftermarket intake, put 2 1/4 duals on them with a divider pipe before the tranny, good mufflers and you'll get a totally different very good hot rod engine that'll even give you satisfactory mileage. No kidding.
     

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