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Discussion Starter · #1 ·
can anyone explain to me why AAN engines seem to only spin the rod bearing on cylinder 4? it might be just me but i've had 3 AAN engines in my possession that have all spun the bearing on cylinder 4 and one engine came with a busted rod and a fist sized hole in the block on said cylinder. is there an oiling issue on this cylinder? something with the oil baffle? has anyone else noticed this trend?
 

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that is very strange. Never seen a rod bearing issue on any 5 cylinder that i have had apart.
 

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me either. what rod bearings? clearances of the good bearings? to me the coated ones seem like they are on the tight side.
 

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I have seen two 5-cylinders spin a rod bearing. One was a 10-valve and the other was a 20-valve engine. Both were directly caused by low oil level leading to low oil pressure. Both engines spun #3 rod bearing but the crank was not hurt.
 

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Discussion Starter · #7 ·
The fourth main cap has the thrust washers on it not the rods. every single engine i've taken apart has has OEM rod bearings so i'd assume they are the original bearings. first engine had 113,000 miles on it when it spun, the second engine had 156,000 miles on it and the third had 160,000 miles. i wonder if it would relate to the oil being ran in the engine. i use just regular castrol 10W-30 oil with the over sized mann oil filter on all of my engines. plus the second engine with 156,000 has a very very large oil cooler instead of the puny stock one.
 

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do you have an oil pressure gauge?
 

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well, why not start by checking clearances? I think an engine block pumps oil to the crank to support it and then oil makes its way through holes to rod journals to support rods. any obstruction or excessive clearance that relates to the rod getting oil could be a problem. So what is different for rod 4? does it share its oil with another rod bearing while the others do not, etc? a problem with oil pressure loss or obstruction at the main? just spit-ballin here
 

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Cylinder number 4 most prone to knock with the intake and exhaust manifold compo in use? A lot of times failing rod bearing it isn't an oiling problem, even most like to think so. Knocking and even just over advanced timing without any hint of knock can hammer out rod bearings.
 

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3BI5 said:
Cylinder number 4 most prone to knock with the intake and exhaust manifold compo in use? A lot of times failing rod bearing it isn't an oiling problem, even most like to think so. Knocking and even just over advanced timing without any hint of knock can hammer out rod bearings.
most likely idea yet, methinks. Same engine management/manifolds/turbo system on each engine, correct?
 

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I would like to know how much these three aan engines were running and what management. I do not disagree with the extra stress idea being harder on everything even without knock being present but still it seems unlikely to make a bearing actually FAIL if the oiling it good.
 

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I thought #4 was the cylinder that got the hottest. Somewhere on here someone pointed out that #4 was generally the cylinder with the worst bore wear and that for various reasons it ran the hottest/was most likely to detonate.
 

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The thing you are not telling the board is your experiments with the Motronic ECU.
The reason you are spinning nr4 is because you are running a bad tune, plain and simple. As said before, nr4 is most prone to knock.
 

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Discussion Starter · #16 ·
not asking for your opinion PRJ. 2 of the 3 engines where bone stock and never modified. only one that had modifications to the ECU was my personal car. so explain that one smart guy.
 

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Discussion Starter · #18 ·
so your saying 93 octane fuel and the factory tuning tuning is crap? in a cars that are stock? my personal car may be crap tuning but you have to learn somehow since theres no information out there but my car always ran on sunoco 93 and VP 110 fuel so your half wrong still. like i asked you before, stay out of my threads. is that too hard for you to do? i dont want your input, go bother someone who enjoys constructive criticism because i dont. i dont come in your threads and say crap or bother you at all. get it through your head PRJ, i dont care what you know or what you have to say regardless. plain and simple.
 

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tuning usually bends a rod, although a rod bearing issue could help that rod to bend. the question is: when pushed, and rods fail, does anyone find the rod bearing area to also have issues or do people just stop looking at what went wrong once they see the bent rod? I think that would tell us if the bearing area is impacted substantially by cylinder pressure that is abnormally high.
 

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vwnut8392 said:
so your saying 93 octane fuel and the factory tuning tuning is crap? in a cars that are stock? my personal car may be crap tuning but you have to learn somehow since theres no information out there but my car always ran on sunoco 93 and VP 110 fuel so your half wrong still. like i asked you before, stay out of my threads. is that too hard for you to do? i dont want your input, go bother someone who enjoys constructive criticism because i dont. i dont come in your threads and say crap or bother you at all. get it through your head PRJ, i dont care what you know or what you have to say regardless. plain and simple.
1. It is an open resource, I may say what I want, where I want. You are no one to tell me anything.
2. Unless you owned the car from new, you have no idea what it ran before.

I literally have thousands of logs, and nr4 starts knocking first in at least 90% of cases.
 
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