Main bearing and rod bearing problems

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  1. #1
    Senior Member Array 03yllwcobra's Avatar
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    Default Main bearing and rod bearing problems

    anyone have any ideas what could cause this damage? the car still ran when I pulled it apart and made over 80psi oil pressure, I sent in an oil sample and it came back with high lead content.


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  3. #2

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    You are starving the bearings for oil, Nick.

    Usually this comes from a low oil level in the crankcase, a high volume pump in a low volume pan, a high pressure pump in a low volume pan, extended (2 secs or more) acceleration or braking that uncovers the pickup at elevated engine rpms or hard cornering that uncovers the pickup for 2 secs or more. An oil pickup that is too high in the oil pan will also cause this sort of failure. A high pickup placement means the pan capacity has been effectively reduced because the pickup can not stay below the oil level in the pan. The proper distance off the bottom of the oil pan is ~5/16" (0.3125").

    The damage you are seeing requires multiple instances or occurrences of the oil starvation problem while under power to occur.


    Ed


    p.s. Not to be the grim reaper but — you ought to also check your cam saddles in the heads. The cams on an OHC engine are the last items to get oiled. If the rods and mains were getting starved you have a high probable starvation of the cams and cam saddles in the heads.

    p.p.s. Do you have any pics of the crank, Nick?
    Last edited by eschaider; 07-07-2020 at 06:51 PM. Reason: Added Postscript

  4. #3
    Senior Member Array 03yllwcobra's Avatar
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    I didn’t take a picture of the crank but the crank looked perfect, except the #4 main which is the bearing that looks burnt. I put the engine back together to take to a machine shop. I was told this could be caused by air in the oil also.

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    Air in the oil is either from foaming (typically caused by overfill) or uncovering the oil pickup, Nick.

    In the OH BTW category, I ran into a shop at PRI two years ago that is in Denver and does some of the most amazing crank repair I have ever seen. The pic below is an exaggerated journal failure that the shop engineered to show their capabilities. Take a look,

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    When you see it up close it is even more impressive. No air bubbles anywhere in the weld and the finished cranks are nitrided to restore the surface hardness. Before repair both sides looked the same. After repair one side actually looked better than new!

    These guys are magicians! And they're pricing is reasonable. If you needed a new crank they could take your dead crank repair it, give you full radius journals everywhere, nitride it and do the whole job for about $900 two years ago and that assumed they had to repair all the rods. Their company name is Mile High Crankshafts. Nice guys, the owner is an old guy that was doing cranks when Christ was a Corporal. They are easy to talk to. and flat out wizards with cranks!


    Ed
    Last edited by eschaider; 07-07-2020 at 08:02 PM. Reason: Spelling and Grammar

  7. #5
    Senior Member Array 03yllwcobra's Avatar
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    My crank isn't that bad, but thanks for the recommendation. I can barely feel the scuffs with my fingernail on the #4 journal.

  8. #6

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    You might be able to get away with just a polish depending on the final journal size after polishing.


    Ed

  9. #7
    Senior Member Array badcobra's Avatar
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    Having a standalone computer is an invaluable tool, that when used properly, could have prevented this. Your idle oil pressure may have 'appeared' fine, but what was it at the track or street during a pass at say 6500rpm? I guarantee you would have seen pressure problems if you were looking at your logs. I am a big believer in spending time looking at your log files and trying to identify problems/trends. Chances are you need to adjust that pickup clearance and possibly add more oil. When you get the car up and running again, use the tools you have at your disposal to your advantage. I am not super familiar with the capabilities of the ProEFI system, but you can likely create a failsafe for oil pressure if you wanted to like most standalone computer systems. Good luck

  10. #8

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    Tony's thoughts are spot on Nick. If you were monitoring oil pressure it might be worth a look back to see if you can find any suspicious events.

    In addition to the monitoring you might want to investigate the engine failsafe's that ProEFI built in. I know they have some fairly sophisticated knock detection and suppression capabilities. I suspect they also have some failsafes for low oil pressure, low fuel pressure etc. It would be worth the time to search them out and enable them with triggering thresholds you feel comfortable with.


    Ed

  11. #9

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    Looks like oil starvation from any number of things. What weight oil are you running? How many miles are on the engine? Air in the oil is also a possibility. This could be from the oil pickup tube being too far from the pan, wrong oil weight, overfill etc.

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    Senior Member Array 03yllwcobra's Avatar
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    The engine was practically brand new less then 100 miles and 3 dyno pulls. I was running 20-50 oil. I spoke the John at accufab about this and we came up with a number of ideas from oil weight, I need a feed restrictor on turbo and some other little things to check. I will indeed check the pan clearance, I just assumed that the persons that built the engine did it. I’m going to be taking the long block to TKM in NC as they are close too me and have a pretty good reputation from guys in my area.

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    Senior Member Array badcobra's Avatar
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    I'm sure John said that's not the right oil. Should be 5 or 10w30 in most cases. I run 10w30 personally

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    Quote Originally Posted by 03yllwcobra View Post
    The engine was practically brand new less then 100 miles and 3 dyno pulls. I was running 20-50 oil. I spoke the John at accufab about this and we came up with a number of ideas from oil weight, I need a feed restrictor on turbo and some other little things to check. I will indeed check the pan clearance, I just assumed that the persons that built the engine did it. I’m going to be taking the long block to TKM in NC as they are close too me and have a pretty good reputation from guys in my area.
    Nick,

    As you know I am a big fan of DIY when it comes to engine builds just because of all the detail that needs to be attended to, If you don't have the time, tools or inclination then pick the best you can find. If I had someone build mine the man I would go to without even a moment's second thought would be Michael Rauscher at L&M.

    The difference between the 10W and 20W oil versions is just the cold cranking viscosity. In cold country the 10W oil is more friendly at cold start. After the engines come up to temp the viscosity is for all intents and purposes the same — 50 weight. If you are a little gun-shy about the 50 weight at temperature there are some 40 weight alternatives, I believe 15W 40 if I am not mistaken.

    That said I do not believe the failure was lubricant choice related. My suspicion is that the engine uncovered the pickup and drew in air on multiple occasions. the pregnant question is what was happening when this occurred. all the guys have come up with good valid alternatives. If the pan gets overfilled the crank can aerate the oil (foam it up) and if the pickup draws in some of the foamy oil the air in th foam will do the damage to the bearings you are seeing.

    If you are using a stock pan and a stock Cobra volume pump (I think this model is you) you want to run one extra quart of oil in the pan because the wetting of the inside of the engine and the oil in suspension as it waits to return to the pan will approximate a quart. The extra quart will keep your pickup under oil where it belongs during engine operation.

    Some pickups have become incorrectly positioned with respect to the pan bottom. The recommended spacing is 5/16 (0.3125") clearance off the bottom of the pan. If you are closer the inlet to the oil pump will be throttled by the reduced clearance and if you are significantly more, greater than ⅜" (0.375") you begin to literally reduce the volume of the pan because of the oil below the pickup which is inaccessible to the oil pump.

    Assuming you had an extra quart of oil in the pan, my bet is pickup placement / position. Put a few drops of oil on the bottom of the pan and the bottom of the pickup. Put a play dough or clay mini hamburger on the pickup and then put the pan on the block snugging down all the pan bolts. Take the pan back off, cut through the clay and measure the thickness at the thinest point. You want to see 5/16". If it is skinny slightly bend the pickup up to get the clearance you want.

    Sometimes a pan will get a dent in the bottom decreasing the clearance. If yours has be sure to un-dent it before final assembly.

    Let us know what you find.


    Ed
    Last edited by eschaider; 09-19-2020 at 12:02 PM. Reason: Spelling & Grammar

  15. #13
    Senior Member Array 03yllwcobra's Avatar
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    I'm running the canton 7qt pan and a HV pump with billet gears. I actually put 1.5 quarts extra in, around 10qts total because of the external oil filter mount and all the lines associated with that. I will definitely be checking the oil pickup clearance with the pan.

  16. #14

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    Quote Originally Posted by 03yllwcobra View Post
    I'm running the canton 7qt pan and a HV pump with billet gears. I actually put 1.5 quarts extra in, around 10qts total because of the external oil filter mount and all the lines associated with that. I will definitely be checking the oil pickup clearance with the pan.
    All good choices. Think about 7+1 quarts in the pan, plus 1 quart for the filter and about half a quart for the lines. It is always an interesting experiment to take the pan when it is off the car and fill it with water. Check the level at 7, 8 and 9 qts to see how high it comes. Remember when the engine is running you will use 1 qt to wet the insides of the engine. In the FWIW category, the off the top of my head observation is that your 10 - 10.5 qts is a good number. When the engine is running the oil level in the pan should be somewhere between the 8 and 9 qt level you measured with the pan off.

    Because you are using an aftermarket pan — even though it is a good one, increasingly I am becoming suspect of the pickup to pan clearance. It will be interesting to see what your measurements show for this dimension.



    Ed
    Last edited by eschaider; 07-11-2020 at 12:26 PM. Reason: Spelling and Grammar

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    Senior Member Array badcobra's Avatar
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    Some commentary about oil from J Mihovetz

    “The oil thing is funny. To be specific, I use different types of oil depending on what I am doing. Basically 5W30 though. Royal Purple mostly. The lash adjusters dictate the use of the 5W30 oil. Then the clearance of the rest of the motor revolves around that.

    It is true that the Ford GT uses 5W50 oil, HOWEVER, the lash adjusters are specifically calibrated in that engine for that oil. AND I can tell you for a fact that 5W30 does not work in the Ford GT because I already did that on the dyno and it lost 15hp on the dyno back to back. As it turns out the reason it lost hp was the thinner oil is more easily compressed in the lash adjuster and the engine effectively thinks the cam is smaller because it is now easier to depress the lash adjuster than to open the valve. Basically the cam profile is the problem in that specific application. The thicker oil is the band aid.
    Regarding the oil, I'd personally prefer 5W30."

    "Here's a good one for you. A guy calls me yesterday and wants to pick my brain. He's got a sand buggy with a 4.6 stock motor with small turbos. He says it runs good but won't rev well. I ask him what kind of oil is he running, he says what difference does it make. I say it makes a lot of difference, just answer the question. He says 20W50. I tell him it won't ever work and he proceeds to argue with me for 20 minutes about how it works in small block Chevys. I tell him to look at the oil filler cap and tell me what it says. He comes back and says 5W20. So now we determine that he can read, he just can't follow directions. I tell him to spend 20 bucks, change the oil, run it 20 minutes and everything will be fine. He proceeds to tell me that I am a prick. I tell him that yes I am but I am the prick with the right answer and that's all that matters."
    Mihovetz

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