Re: #6/#5 spun rod bearing ?
[Re: Thumperdart]
#1069298
09/06/11 03:51 PM
09/06/11 03:51 PM
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TomsCharger70
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Ive been thinking about the spun rod bearing. One thing that crossed my mind is that maybe the reason is that I used to thick oil, 15W20 and ran to much oil pressure in the engine. Cold the oil pressure was 100psi and once engine got warm it was about 60psi. Weirdly the oil pressure did not go up by much at high RPM, about 75psi @ ~7000rpm. The clearances were/are quite loose in the engine, its an old Pro Stock engine. The bearing clearances for main and rod bearings were, if my memory serves me right, in the .0025 something (I cant find my rebuild memo). I left the clearances where they where when I put new bearings in it, clearances were/are a tad loose, but its an old race engine, and my plan was when I bought the engine, that Ill do a service and drive it as is for a season or two, then do a complete rebuild of the bottom end. ..Any ways... The thing that came to my mind is that was the oil to thick and the pressure to high when cold, could that have caused the bearing to spin??? So what do you think, did I up??? /Tom
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Re: #6/#5 spun rod bearing ?
[Re: Thumperdart]
#1069299
09/06/11 03:53 PM
09/06/11 03:53 PM
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68LAR
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Yes that and the excessively THICK 98 cold psi and 65 at idle doesn`t seem ideal to me personally. With fairly large bearing clearances in my motor I still run 5w30-10w30 oil and even though I have an 8-quart pan, I run bet 6-7 quarts and have about 70psi cold and 30-40 at idle/cruise.
Cool, you're entitled to your opinion, but tell me this, how many cases of rod bearing failure have you heard of, that was attributed to too high of oil pressure? I'm guessing that I'm allot older than you and I've NEVER heard of high oil pressure causing bearing failure. Granted it robs horsepower, but this is my choice to have higher pressure......... I've heard of many, many more failures due to too low of oil pressure, rather than too high.
Last edited by 68LAR; 09/06/11 04:03 PM.
4 speed street legal. Best time 10.99 @ 124 mph on 93 octane pump gas @ 3926# total weight
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Re: #6/#5 spun rod bearing ?
[Re: 68LAR]
#1069300
09/06/11 04:05 PM
09/06/11 04:05 PM
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TomsCharger70
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I kinda think there is a possibility that high pressure and loose oil viscosity may cause a bearing to spin, it comes down to physics. IF the clearances are to loose, the thick oil circulating at high pressure, may cause such a "drag", no idea what to call it in English, but the forces at play get so high, that it rotates the bearing?
/Tom
Last edited by TomsCharger70; 09/06/11 04:07 PM.
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Re: #6/#5 spun rod bearing ?
[Re: TomsCharger70]
#1069301
09/06/11 04:13 PM
09/06/11 04:13 PM
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kinda think there is a possibility that high pressure and loose oil viscosity may cause a bearing to spin, it comes down to physics. IF the clearances are to loose, the thick oil circulating at high pressure, may cause such a "drag", no idea what to call it in English, but the forces at play get so high, that it rotates the bearing?
Bearings are "indexed" so they won't rotate. One reason of what causes a spun bearing is metal to metal contact, or, lose of oil pressure. Your theory may be valid, I'm no physisist, but I'd have to see documented proof. My bearing clearances are .0025", which is in line for my type of engine usage. Nothing exotic, here.
4 speed street legal. Best time 10.99 @ 124 mph on 93 octane pump gas @ 3926# total weight
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Re: #6/#5 spun rod bearing ?
[Re: 68LAR]
#1069302
09/06/11 04:15 PM
09/06/11 04:15 PM
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Moparnut426
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Yes that and the excessively THICK 98 cold psi and 65 at idle doesn`t seem ideal to me personally. With fairly large bearing clearances in my motor I still run 5w30-10w30 oil and even though I have an 8-quart pan, I run bet 6-7 quarts and have about 70psi cold and 30-40 at idle/cruise.
Cool, you're entitled to your opinion, but tell me this, how many cases of rod bearing failure have you heard of, that was attributed to too high of oil pressure? I'm guessing that I'm allot older than you and I've NEVER heard of high oil pressure causing bearing failure. Granted it robs horsepower, but this is my choice to have higher pressure......... I've heard of many, many more failures due to too low of oil pressure, rather than too high.
I have heard of it "washing" the bearings, That was in an 8500rpm dirt latemodel engine. It would accually just force the oil out of the bearing, I dont understand it for sure either, but the engine im talking about ran 20w50 with .003 rods, and mains, and he had 95+ psi oilpressure, and had a bearing failure on his small block, when he changed the pump to no more than 65psi at the same rpm the bearing issue went away.
so from that I honestly dont know why...
Kasey
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Re: #6/#5 spun rod bearing ?
[Re: 68LAR]
#1069304
09/06/11 04:44 PM
09/06/11 04:44 PM
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Are you oiling the rockers full time? If not don't restrict the oil to rockers The reason being that the stock oiling through the cam only allows oil to the rockers around 15 camshaft degrees....
Ya, my blocks are all stock oiling systems. So I have to live with what I got, and do the yearly tare down and inspection from now on. Thanks to all for good info, Larry
the reality is that the engine needs to come apart completely now anyway, so it's a good time to do the oiling mods and get it over with. there's no reason a street/strip combo should have that much oil pressure. pressure is a result of restriction, keep that in mind. when the engine was built, was each rod checked for size and roundness? oil clearance doesn't mean much if the bearing lacks themproper crush to hold it in place. those index tabs you speak of are just that, a way to locate the bearing. they're in not intended to keep one from spinning in the housing bore. as far as restricting oil to the top end, hogwash. it's a driver, not an all out race car. do the oiling mods in order to get the volume of oil to the places it needs to be. use due diligence in checking housing bore sizes and other standard engine building practices and move on. engine failures are costly, doing it any way but the right way the 2nd time around is even more costly. best of luck.
machine shop owner and engine builder
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Re: #6/#5 spun rod bearing ?
[Re: maximum entropy]
#1069306
09/06/11 05:08 PM
09/06/11 05:08 PM
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Joined: Sep 2007
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TomsCharger70
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DUDE, you have two different kinds of rod nuts. or am i hallucinating?
Nope, you are correct. A rod nut is a rod nut... Loos weird, but does its job.. story is that previous owner of the engine did a service to it, changed out bearings. He lost two of the nuts, but being a race shop owner he just went into his shop and looked what he could find on his shelves...
/Tom
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Re: #6/#5 spun rod bearing ?
[Re: Performance Only]
#1069307
09/06/11 05:51 PM
09/06/11 05:51 PM
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the reality is that the engine needs to come apart completely now anyway, so it's a good time to do the oiling mods and get it over with. there's no reason a street/strip combo should have that much oil pressure. pressure is a result of restriction, keep that in mind. when the engine was built, was each rod checked for size and roundness? oil clearance doesn't mean much if the bearing lacks themproper crush to hold it in place. those index tabs you speak of are just that, a way to locate the bearing. they're in not intended to keep one from spinning in the housing bore. as far as restricting oil to the top end, hogwash. it's a driver, not an all out race car. do the oiling mods in order to get the volume of oil to the places it needs to be. use due diligence in checking housing bore sizes and other standard engine building practices and move on. engine failures are costly, doing it any way but the right way the 2nd time around is even more costly. best of luck.
My clearances were checked prior to the build in 2004, as stated, rods and mains WERE all at .0025". The increase in oil pressure is done by me adjusting the pressure relief spring in the oil pump, up a tad. With the relief spring untouched, my pressure was at 65 psi cold and 45 hot. I wasn't comfortable with that. Again, a question of what oil mods I should make, IF any, still has to be anwered. Remember, this is NOT a dedicated race engine. Most of the time it is street driven. DO I NEED TO MODIFY THE OILING SYSTEM????? Right now, to tell you the truth, I'm confused and getting mixed opinions as to IF I do need any mods at all.
Thanks for any input,
Last edited by 68LAR; 09/06/11 06:00 PM.
4 speed street legal. Best time 10.99 @ 124 mph on 93 octane pump gas @ 3926# total weight
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Re: #6/#5 spun rod bearing ?
[Re: 68LAR]
#1069309
09/06/11 07:16 PM
09/06/11 07:16 PM
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the reality is that the engine needs to come apart completely now anyway, so it's a good time to do the oiling mods and get it over with. there's no reason a street/strip combo should have that much oil pressure. pressure is a result of restriction, keep that in mind. when the engine was built, was each rod checked for size and roundness? oil clearance doesn't mean much if the bearing lacks themproper crush to hold it in place. those index tabs you speak of are just that, a way to locate the bearing. they're in not intended to keep one from spinning in the housing bore. as far as restricting oil to the top end, hogwash. it's a driver, not an all out race car. do the oiling mods in order to get the volume of oil to the places it needs to be. use due diligence in checking housing bore sizes and other standard engine building practices and move on. engine failures are costly, doing it any way but the right way the 2nd time around is even more costly. best of luck.
My clearances were checked prior to the build in 2004, as stated, rods and mains WERE all at .0025". The increase in oil pressure is done by me adjusting the pressure relief spring in the oil pump, up a tad. With the relief spring untouched, my pressure was at 65 psi cold and 45 hot. I wasn't comfortable with that. Again, a question of what oil mods I should make, IF any, still has to be anwered. Remember, this is NOT a dedicated race engine. Most of the time it is street driven. DO I NEED TO MODIFY THE OILING SYSTEM????? Right now, to tell you the truth, I'm confused and getting mixed opinions as to IF I do need any mods at all.
Thanks for any input,
i'm just trying to help. did you ever check the housing bores for size and roundness? frankly, most home builders don't because they don't have the proper tools or experience to do it. 65 psi cold is a smidgen low on a cold motor, but not what i would be concerned about. what was the pressure hot at 6000 rpm? that's way more important in my book. i'm just saying, IMO you should do the oiling mods. it's not voodoo, it helps. the basic mods are fine although i still prefer the 1/2" oil pickup. are you running a std or high volume oil pump?
machine shop owner and engine builder
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Re: #6/#5 spun rod bearing ?
[Re: 68LAR]
#1069310
09/06/11 07:16 PM
09/06/11 07:16 PM
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ZIPPY
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I'd suggest get chuck senatore's old book, and ream + clean up the passages between the oil galley and the mains the way it's spelled out in there. Other books say it in one sentence, but that one explains exactly what to do. If you've never checked out what a mess those particular oil passages are in a stock block you're in for a real treat. It would not surprise me if you found a couple holes that are 2/3 the size of the others, and that would do it. For the type of use, I would not restrict the oil to the rocker shafts with an stock (other than above) system. Considering the preference for high viscosity oil/additive, that stp adds a whole bunch of viscosity....but if you like it, go ahead and use it....I also think it's a good candiate for the old direct connection "hemi" 1/2" oil pickup, radius and blend the pickup passage modification. SAE 50 and 40 weight were commonly used back when the books detailing those mods came out. All that will give you more flow (volume, not pressure) through the system......it should definitely help
Rich H.
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Re: #6/#5 spun rod bearing ?
[Re: 68LAR]
#1069311
09/06/11 07:36 PM
09/06/11 07:36 PM
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Thumperdart
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Yes that and the excessively THICK 98 cold psi and 65 at idle doesn`t seem ideal to me personally. With fairly large bearing clearances in my motor I still run 5w30-10w30 oil and even though I have an 8-quart pan, I run bet 6-7 quarts and have about 70psi cold and 30-40 at idle/cruise.
Cool, you're entitled to your opinion, but tell me this, how many cases of rod bearing failure have you heard of, that was attributed to too high of oil pressure? I'm guessing that I'm allot older than you and I've NEVER heard of high oil pressure causing bearing failure. Granted it robs horsepower, but this is my choice to have higher pressure......... I've heard of many, many more failures due to too low of oil pressure, rather than too high.
Settle down skippy...............wasn`t refering to the spun bearing just damn thick oil that`s all and another thing, older DOESN`T make you smarter. Now where were we?
72 Dart 470 n/a BB stroker street car `THUMPER`...Check me out on FB Dominic Thumper for videos and lots of carb pics......760-900-3895.....
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Re: #6/#5 spun rod bearing ?
[Re: Performance Only]
#1069312
09/06/11 07:40 PM
09/06/11 07:40 PM
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i'm just trying to help. did you ever check the housing bores for size and roundness? frankly, most home builders don't because they don't have the proper tools or experience to do it. 65 psi cold is a smidgen low on a cold motor, but not what i would be concerned about. what was the pressure hot at 6000 rpm? that's way more important in my book. i'm just saying, IMO you should do the oiling mods. it's not voodoo, it helps. the basic mods are fine although i still prefer the 1/2" oil pickup. are you running a std or high volume oil pump?
I know you are trying to help. It's hard to show feelings with a key board. I appreciate all of the replies so far, really! I did not check bore size because of the reason you mentioned. 65 psi was cold idle. At 2200 rpm it was at 75 rpm. I didn't take it up higher than 3500 and it remained at 75. When I raced it with the engine at temp. my oil pressure sets, or sat at, 75-80 psi at 6500 rpm. With that, what mod would you recommend? I'm leaning toward the one that blocks the oil from #4 to the cam bearing and drill and tap in a restrictor into the main oil galleies for rocker lubrication. If any mods, to me, this one as described in the "Power Adder" section, would work best on a street/strip engine like mine.
Quote:
Considering the preference for high viscosity oil/additive, that stp adds a whole bunch of viscosity....but if you like it, go ahead and use it....I also think it's a good candiate for the old direct connection "hemi" 1/2" oil pickup, radius and blend the pickup passage modification. SAE 50 and 40 weight were commonly used back when the books detailing those mods came out.
I guess that I forgot to mention. I already have a 1/2" pick up with a high volume pump.
Last edited by 68LAR; 09/06/11 07:49 PM.
4 speed street legal. Best time 10.99 @ 124 mph on 93 octane pump gas @ 3926# total weight
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