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Technical Engine Block Porosity

Discussion in 'Traditional Hot Rods' started by ande-bob, Apr 16, 2021.

  1. ande-bob
    Joined: Apr 9, 2008
    Posts: 33

    ande-bob
    Member

    Hi, I've been running my 1930 Model A for 21 years with an oil pressure issue. The engine is great and as I said no issues for all these years. The engine is a stock bore 1970 Dodge/Chrysler 383. I acquired this engine as a "recently overhauled" unit. During the car build, I pulled the heads to see the bores. Honing was still clearly evident and no lip so buttoned it up and carried on. First thing I noticed was when the engine was fully warmed and in gear, the oil pressure was only 10psi. Touch the gas and it goes to 30+. While the car was blown apart for paint, I delved deeper into the engine. Crank was badly scored, so ditched everything but the block. Machine shop fully prepped the block and I reassembled it with a perfect replacement rotating assembly and rebuilt heads. Car gets final assembled and on initial firing, the same condition occurred. I and my favourite shop chased this issue several times. There's lots of oil getting to the top when its running with low pressure. Cold start 50psi+ warming to 180° after driving a bit then stop at a light in gear and its 10psi. Touch the gas and its 35psi. all day long. There are no oil leaks into coolant or externally. My most excellent mechanic figures the block is porous somewhere and I agree. There is no engine noise like cam bearings or something and the condition carried over into the new assembly with all different parts. Does anyone have any experience on how to trace or prove a porous block?
     
  2. Big block Mopar can have oil pressure issues solved easily,,,since they use an external oil pump
    They make an adjustable cap that goes on top of the relief spring .
    Milodon made it ,,,,but it can easily be replicated at home.
    Or,,,,,just remove the stock spring cover cap,,,,and place a thin shim over the spring end .
    Check it out,,,,,,really easy fix .

    Tommy
     
    JC Sparks, fauj and Deuces like this.
  3. I got a buddy with a 440 in his hot rod. When he bought it, I drove it about 50 miles back to town and as I stopped at a signal light, the oil pressure went to zero so I shut it off!. Let it sit for a few minutes and fired it up to see good oil pressure again. The owner of the car pulled the motor and tore it down to find the oil pickup was not screwed in tight to the pump and would "flop" around when braking or accelerating and apparently suck air.
     
  4. Greg Rogers
    Joined: Oct 11, 2016
    Posts: 425

    Greg Rogers
    Member

    Isn't 10psi per 1000rpm hot considered OK? Thus 800 idle 10 psi? Doesn't seem so bad. Seems like the old idiot lights wouldn't come on until 5 psi..?
     
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  5. Blues4U
    Joined: Oct 1, 2015
    Posts: 5,701

    Blues4U
    Member
    from So Cal

    Yeah, I don't see the problem. This is the 2nd thread this week I think with the same concern, and basically there is nothing to be concerned about. 10 psi at idle when the engine is at operating temperature is normal, why would you expect it to be higher? As Greg posted just above me, the typical rule of thumb is 10 psi per 1000 rpm, at idle 10 psi is right on. Quit worrying and drive it.
     
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  6. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 3,394

    2OLD2FAST
    Member
    from illinois

    In the 60's as a line mechanic , being the young guy in the shop. I used to get the C-50 grain trucks , many of those had 250" sixes or 283's -348's. These engines worked HARD , many also only produced 25- 30 psi oil pressure @ 2500 rpm up , maybe 5-10 psi @ idle , ran forever if you could keep exhaust valves in ' em !
     
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  7. MoePower
    Joined: Jul 12, 2004
    Posts: 207

    MoePower
    ALLIANCE MEMBER
    from Omro, WI

    My OT Satellite has a 440 that's done this since day one of the engine rebuild. No issues, I stopped worrying about it.
     
  8. J. A. Miller
    Joined: Dec 30, 2010
    Posts: 1,596

    J. A. Miller
    ALLIANCE MEMBER
    from Central NY

    Add a quart of STP!:rolleyes::D
     
    ekimneirbo likes this.
  9. sunbeam
    Joined: Oct 22, 2010
    Posts: 5,277

    sunbeam
    Member

    Ford had issues around 64 some FEs would seep coolant trough the side of the block and Ford would replace the short blocks under warranty.. I grabbed a couple sand blasted the block and painted them with fiberglass resin and ran them with no issues.
     
  10. greybeard360
    Joined: Feb 28, 2008
    Posts: 1,748

    greybeard360
    Member

    Adding a washer to the relief valve won't buy you anything at an idle... pressure isn't high enough for it to open as it is...... that is an old myth.

    My AMC race car idled at 15-20 psi when warm, ran thru the lights at 7200 with 60 psi..... right where the relief valve would open. I ran it for 5 years that way. I pulled the pan and checked everything after 3 years.... bearings were all perfect.

    64 Dodge NSS car. 500 CID B engine. Idled at 12 psi, 70 psi at 7000 .... ran mid 9's without any issues.

    I had an OT Dodge van with a 360. In the summer it got to where the oil light would flicker and guage would drop to 0. I put a manual gauge on it and it was idling hot at 8 psi, the threshold of the light coming on. I changed to 20-50 for the summer and cured that problem....idled at 12 psi :). It ran that way to over 130k miles...... then some idiot pulled out in front of me and totaled it. I loved that van too !!!
     
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  11. Father in-law was a mechanic for a GM dealership in the late 60's (maybe early 70's). According to him, the larger Buick engines (when new) had so little oil pressure at idle, the dash warning light would flicker. Supposedly they just changed the sensor to one that triggered at a lower psi.

    Obviously this issue worries you a bit so I'd say, drop the pan and check some bearings ... if they look good, put the pan back on and keep running it.
     
  12. TRENDZ
    Joined: Oct 16, 2018
    Posts: 310

    TRENDZ

    Make sure your rocker shafts are not upside down.
    Your symptoms indicate they are.
     
    Frankie47 likes this.
  13. ande-bob
    Joined: Apr 9, 2008
    Posts: 33

    ande-bob
    Member

    Not upside down. This was checked while we had the rocker covers off to observe whether enough oil was getting to the top. Thanks for your reply.
     
  14. ande-bob
    Joined: Apr 9, 2008
    Posts: 33

    ande-bob
    Member

    Frankly, after investigating this issue 15 or 20 years ago, and having no issues in the meantime, I, personally, am fine with it. The car has less than 20k miles on it. Unfortunately, I'm trying to sell the car and its killed a fair deal and likely will again. I have another engine block with a proven history that I've actually owned twice (long story) that I could swap in but a lot of expense for nothing if the problem isn't porosity. Thanks
     
  15. ande-bob
    Joined: Apr 9, 2008
    Posts: 33

    ande-bob
    Member

    The hangup is that this issue carried over from a block with one set of internals to the same block with an entirely different set. The only component in the "new" configuration was the block itself. I assembled the engine myself after the machine shop had its way with it (new main, rod and cam bearings, polished crank, new cam etc) and checked all the tolerances as I went. The issue reappeared immediately on its first run and continues after 20k miles. Thorny issue for me as I want to sell this car and its already killed one sale. Thanks for your comment.
     
  16. TRENDZ
    Joined: Oct 16, 2018
    Posts: 310

    TRENDZ

    Low oil pressure and a lot of oil up top.

    This happens when any of the following occur:
    1) Rocker shafts are upside down.
    2) Full grooved #4 cam bearing.
    3) Groove cut into #4 cam bearing journal.

    If any one of those things are done to a B/RB engine, (tricks from the 80s)you will get the symptoms you are having.
    Along with the low oil pressure reading at idle, and excessive oil up top, you will also see a poorly lubricated #4 main bearing. Even with “good” higher rpm gauge readings.
     
  17. Blues4U
    Joined: Oct 1, 2015
    Posts: 5,701

    Blues4U
    Member
    from So Cal

    Well, I still don't think that 10 psi at idle when hot is a problem, but, I looked through the thread again and didn't see what viscosity grade oil you're running. What is it?
     
  18. ande-bob
    Joined: Apr 9, 2008
    Posts: 33

    ande-bob
    Member

    After break-in, Mobil 1 Synthetic 10-30 all its life. Never considered heavier oil as all tolerances were in spec. I've used 20-50 in other applications with varying results. This engine is tight so higher viscosity could potentially be harmful. The oil I used in the earlier configuration was just ordinary 10-30, probably Quaker State, but can't remember its so long ago.
     
  19. ande-bob
    Joined: Apr 9, 2008
    Posts: 33

    ande-bob
    Member

    Good to know but none of this was done. When redoing this engine, I considered installing the grooved rear bearing shell available from Mopar Performance but decided against it. Didn't know about any implications at the time. Thanks...everything helps.
     
  20. Blues4U
    Joined: Oct 1, 2015
    Posts: 5,701

    Blues4U
    Member
    from So Cal

    Pressure is a result of resistance to flow. If you want to increase pressure you have to either increase flow, or increase resistance to flow. The technical definition of "viscosity" is "the resistance of a fluid to flow". A higher viscosity oil has more resistance to flow, and will provide increased pressure in the system. You could change the pump to provide increased flow, that would result in higher pressure reading. Or you could rework the engine to provide increased resistance to flow, that would result in higher pressure reading. Or you could increase the viscosity of the oil.

    I'm curious in what way a higher viscosity could be potentially harmful. Perhaps additional start up wear when cold? Yeah, that is a possibility. A lower viscosity will flow out to the extremities faster on startup and potentially reduce wear vs a higher viscosity. But a higher viscosity will provide additional film strength vs lower viscosity under stress, and potentially provide less wear under load at operating temp.

    The viscosity number you need to be concerned with is the 2nd number, the 30 (or 40, or 50, etc). The 1st number just tells you about cold flow properties. Once up to temp it's all about the 2nd number. An SAE 40 (say from either a 10W-40 passenger car oil, or 15W-40 from a diesel engine oil) should net you a bump in your oil pressure at idle. A 5W-40 would get you better flow at startup plus added oil pressure at operating temperature.
     
  21. I kinda doubt you have a porosity problem...what are the chances you'd have two in a row?
    Are you reading the pressure from a KNOWN gauge? Mechanical? Electric? What location?
    Remember... Pressure is the RESISTANCE to flow of a given volume (gallons per minute/hour/mile/revolution, whatever you want to consider). Using 10 psi per 1,000 rpm as a guide, what is the rpm at idle? At 60 mph? What is the indicated oil pressure at those rpm?
    If anything, you MAY have an oil pump that isn't up to snuff, but otherwise, I think you're worried about nothing. Take a perspective buyer for a ride and show them the oil pressure under driving conditions.
     
  22. Beanscoot
    Joined: May 14, 2008
    Posts: 2,049

    Beanscoot
    Member

    Excellent point that a lot of people don't think about, but if one does think about for a bit, entirely makes sense.

    Just out of curiosity, what were those clearances?

    I do agree with the others though, that your oil pressures are fine.

    And you would have to have a pretty porous block to be losing a significant amount of oil from the pump. That sounds like a red herring.
     
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  23. Also,,,,,,we’re assuming all the internal core plugs are in place and sealing well ?
    Is there an unusual amount of oil in the top end,,,,,that could bleed a lot of pressure at low rpm ?
    Tommy
     
  24. chriseakin
    Joined: Jan 21, 2009
    Posts: 381

    chriseakin
    Member

    I don't know if this applies or not, but I remember reading that for some engines they recommend a restrictor in the oil flow to the heads so that the crankshaft bearings are better looked after and there's less accumulation around the valve train.
     
  25. TRENDZ
    Joined: Oct 16, 2018
    Posts: 310

    TRENDZ

    The B/RB mopar engines in stock form don’t require any restrictors. It’s when you install grooved cam bearings, or get a cam from a company that grooves their cams that restrictors are needed.
    The entire top end on both sides of the engine are fed oil through timed drillings in the camshaft. The way it is oiled from the factory is one drilling goes from the main galley, to the #4 cam bearing. The cam bearing has 3 holes. One oil inlet, and an oil outlet for each side. The cam has a hole drilled through it to “connect” the inlet to the outlet in a very short/momentary spurt as the cam rotates.
    Some bearing manufacturers put a groove in the cam bearing that never shuts off the oil to the top end. Some cam companies groove the cam because its easier than a timed drilling.
    Sometimes you end up with a grooved bearing and cam. You flood the top end, and lose oil pressure. You can doo several different things to restrict oil to the top if your cam manufacturer grooved the #4 cam journal.
    The simplest is to remove the rocker shafts and put roll pins in the oil feed drilling in each cylinder head. Some people (if you know ahead of time) install the cam bearing rotated to partially block the feed to the top end. Or you can drill and tap the oil drilling holes at the deck surface and thread in an orfice.
    Very common when using an aftermarket cam.
     
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  26. Budget36
    Joined: Nov 29, 2014
    Posts: 6,767

    Budget36
    Member

    Where would the block be porous that would cause a loss of oil pressure? Just curious.
     
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  27. finn
    Joined: Jan 25, 2006
    Posts: 810

    finn
    Member

    If you’re a curious sort of guy, get a pencil & sheet of graph paper. Along the bottom ordinate mark off rpm in equal intervals from, say 500 rpm to 6000 rpm. On the vertical axis, mark off oil pressure from zero to, say, 100 psi.

    Check and record observed oil pressure every hundred or two hundred rpm and plot the curve.

    You should see a relatively straight line pressure s speed relationship, with an inflection point where the relief valve starts to spill excess pressure.

    Not sure about car engines, but heavy duty engines are designed so that inflection point is a little below peak torque speed. Moving the torque curve around sometimes entailed oil pump design modifications, is wider gears when the peak torque point was desired to be at a lower engine speed.
     
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  28. This is a strange occurrence it seems to me,,,,Mopar always had good oil pressure,,,,a5 least in my experience .
    You kept the original block,,,,,but replaced everything else ?
    I don’t see why,,,,,,because the crank was badly scored ?
    The crank could have easily been ground .010-.010,,,,and been like new again .
    Replaced the rods,,,,,,were the rods in terrible condition,,,,or jus5 wanted new rods ?
    Also,,,,,,are the new rods any better than the old ones ?
    Like some have said,,,,,,side clearance on the rods will lose a lot of oil at low idle.
    Are they aftermarket rods,,,,,,,some replacement rods are notorious for excessive clearance.
    But since these rods usually go in performance engines that spend almost no time at low idle,,,,no one knows this .
    Most racing engines idle at such a rpm,,,,no one would ever know they lose pressure down at that rpm .
    I’m assuming the block was bored,,,,,and new pistons put in ?
    Maybe a new pickup suction tube and a new oil pump too ?
    Any thing else,,,,,I hope we can figure this out .

    Tommy
     
  29. ekimneirbo
    Joined: Apr 29, 2017
    Posts: 1,999

    ekimneirbo
    Member
    from Brooks Ky

    I don't think you mentioned anything about replacing or rebuilding your existing oil pump. I would wonder if the clearance in the pump itself might be the reason. It could have been from wear originally, or just the design and manufacturing tolerances of that brand of pump.
     
  30. I have done a few 440 motors they seem to run higher pressure than chevy motors I have a 513CI RB motor in my gasser it runs 70 psi at 3000 rpm about 180 * at idle [1100] 20/30lbs .I also have 64 plymouth 383 with 40,ooo original miles 60 psi going down the road about15/20 at idle .
     
    Desoto291Hemi likes this.

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