bad main bearings

To expand on my first post about oil gallery plugs, the reason for the engine work is that I had previously re built the engine and it tore up the number 2,3,4 main bearings, I believe the majority of it during break in. The number 1 and 5 bearings still look good. On initial start it had 80-100 lbs of oil pressure, had a heavier spring in the oil pump. After 20 minutes of break in, the hot pressure had dropped to 20 lbs. I changed the oil and filter and still had low pressure. I dropped the pan, put the stock spring back in the pump and after reassembly it still had low pressure. I did neglect to check the main bearings at that time. I then drove it for about 50 miles and it was getting at worst, 5-10 lbs hot at idle, and 26-28 lbs hot at 3000 rpm. Here I am now with the engine apart and think I found the problem, but trying to find the cause of the bearing failure. It has the externally balanced 460 crank in it. I just took the crankshaft to the machine shop to get checked out and see if it is bent or was machined wrong to begin with. If that nets no results than I am going to get the block checked for the line bore. As I assembled it the clearances checked out fine. I am investigating to see if it was faulty machining or if I did not get the oil galleries clean enough before assembly and had some junk go through and ruin the bearings.

On another note, a good friend of mine who is a long time engine builder and racer said he does not like to run externally balanced cast iron crankshafts in preformance engines due to flex at over 6000 rpm. So I believe I am going to look into getting it internally balanced, possibly with a new forged crankshaft. He is a Probe dealer and said he can get a complete 545 stroker kit for it for $2300. It includes the crankshaft, forged pistons, forged rods, bearings, rings, and is already balanced. So I am seriously considering this option as well, and might lok into selling my nearly new Probe 460 pistons and I beam rods to go towards that

Were the bearings put in correctly?

In this case the ext. balance is not the issue. The stock stroke 460 cranks with their 2.500" rod journals are pretty stout.

I figured the balance was not the issue, but if the crank was bent I was considering a new crank since it will be run hard from time to time. Let's see here, I did have the clearances all written down but can't find them at the moment, but they were within spec. I stopped by the machine shop and he said the journals were all perfect on the sizing, which was .010" under. It was in the hot tank getting cleaned and he was going to check it for straightness tomorrow. I am almost positive the block was line honed but it was done a couple years ago. I got the engine done last year, drove it and was not happy with the oil pressure situation and parked it until now when I have the time to pull it apart. I do have the receipts from the machine work, looking for them right now. If the crank checks out then we were going to check the block for straightness on the mains, hopefully finding an answer. The bearings were installed correctly, the are Clevite bearings.

During intial break in I ran 30W Joe Gibbs break in oil. I drained it and ran some rotella for a few miles and then changed again switching to Brad Penn 10W-40 and then 20W-50.

I am using the Kaase oil pump which I am sure is good since it had plenty of pressure to start with and plenty when cold. But as soon as it warms up the pressure is way too low and the machine shop guy said that the bearing failure would cause the loss in oil pressure. I did take the pump apart and the relief valve does move freely.

I think it was caused due to either the crankshaft is slightly bent, main bearing bores are not correct, or I did not get something cleaned out of the oil galleries before assembly. I was very meticulous cleaning the block, and I wonder why the number 2,3,4 main bearings were damaged and not the number 1 and 5 bearings. Like I said hopefully checking the crank and mains will find the answer because I don't want to re assemble anything until I am sure what the problem is. I was wondering if anyone else had run into this type of problem before? Thanks again for all the help, really nice to be able to talk to the experts on here

im thinking the high oil pressure is an indicator of the cause

we have ran 70 to 105 lbs of oil press in many engines with 0 problems @ 7000 and above



this engine probably has a bad line bore

Got any pic. of the bearings?

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The bearings are at the machine shop at the moment, I will get pictures hopefully tomorrow and post them up for everyones inspection. I think I failed to mention that I did add a higher pressure spring to the pump, not sure how that would cause the bearings to go bad but I am open to suggestions. My uncle built many FE engines and always ran high oil pressures and never had a problem caused by high pressure. The bearing failure could have been my fault. I'm not a seasoned engine builder but have built a few and haven't had this problem before, just trying to get the cause figured out so it doesn't happen again. The clearances were within stock specs I believe. I'm at a loss at the moment so that's why I brought it before you guys since you have the most experience with these engines. I don't think I will get a definite answer until the block and crank are fully checked out but I'm at least more informed now than when this whole debacle started