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By Moz - 14 Years Ago
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g'day guys ive got a question for all the crankshaft experts saturday i was looking for a banging (not knocking ) noise in my engine i had the oil pan off so decided to have a look at the main bearings they've only done about 20 k miles # 1 was in great condition removed # 2 & got a surprise the bearing was worn out on the non thrust side on about 1/4 of the bearing from the edge down the crank journal is slightly dark colored like it got hot but is still smooth & not scored at all i checked all the other 3 main bearing & they all look like # 1 does does anyone have an idea about why 4 are like new & 1 is worn out will the crank journal be ok or should i have it checked & would it be safe to put another bearing in # 2 mains. after talking to a friend of mine about a new crank pulley mine has a broken rubber & the ring slides off he sugested it may be getting harmonic vibrations because its out of balance & that maybe what destroyed the # 2 bearing does that sound feasable i would welcome your ideas on the matter as i would like to fix it as soon as possible thanks guys.
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By pegleg - 14 Years Ago
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Moz, the other possibility is that the block is not straight. As in it needs to be line bored. OR the crank journal is not ground correctly (off center), or the crank's got a bit of a bend.
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By MoonShadow - 14 Years Ago
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My "new" 40 over 272 engine, from two years ago, also wiped the number two main. All of the other bearings looked good. The rods on the lobe by the number two main had heated to the point of replacement. Engine ran about 500 miles before the oil pressure dropped. Probably from the bad bearing. My machine shop thought it could have been a clearance problem on the main bearings on that cap. The damper was the same one I sent to Ted for my new engine. He told me it had slipped. Curious coincidence? Anyway block was checked for alignment, rebored to 292, the two rods replaced, and re-balanced. Will be running again this week and back in the 56.
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By Ted - 14 Years Ago
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Moz. Got a picture?
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By Moz - 14 Years Ago
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ted i buttoned it back up so i could move it off the pit but i have to pull the engine out so i will take photo's for you then, im hoping i dont have to get it ground again frank it is possible its the crank this is the one i put in after the original broke i had it checked for cracks & straightness it was so good they only took 20 thou of the mains & 10 thou of the big ends the thing still looks brand new except for the bearing & the fact that journal is a black/blue color i thought it might have been from when the dizzy stripped the hex drive & i was stuck in traffic ith no oil pumping & i couldnt pull over but i should see the same thing on all the bearings & they all still look new.
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By Moz - 14 Years Ago
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chuck that is really interesting i will have to put more thought into this theory the # 2 & # 4 are the two places on the crank most prone to vibration being as # 1 is right behind the pullet & timing chain # 3 is the thrust bearing # 4 is the same as 2 thats where my original crank broke because the cap was loose & # 5 has the smallest section of crankshaft to hold & also has a balances flywheel or flex plate.
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By pegleg - 14 Years Ago
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Moz. I don't remember the stuck in traffic with a bad oil pump part. At this point I'd check everything and replace the bearing. check the rods and all the other mains, and have the crank re-checked and the damper fixed. That may well be the result of running w/o oil press. Ted may be able to tell from a photo, but to sure you'd need to check everything. I would have thought you would've seen a drop in hot oil pressure after the incident.
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By Moz - 14 Years Ago
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frank that was when you got the new dizzy for me nearly 3 years ago now, ive checked all the other mains & big end bearings & there all still like new im asuming that because only 1/4 of the # 2 main is worn out is why there was no drop in hot oil pressure today i was thinking maybe i made them too tight i torqued the mains to 100 ft lbs maybe i should have only gone to 95.
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By Moz - 14 Years Ago
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oh yeah i forgot the banging noise i was looking for is the drive plate bolts are loose & the plates moving on the crank shaft & making the noise
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By rick55 - 14 Years Ago
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Gee, Moz what a saga.
Just get the crank checked and linished if necessary. I wouldn't think the tension you put on the bolts would have anything to o with the bearing failure. It is almost certainly due to lack of oil when the oil pump drive failed. You would always get one bearing to fail before the others, but run it long enough and they would all be toast.
I ran a y block for 10 years with no ring on the harmonic balancer with no noticeable difference to the engine. The crank is still good on that engine.
The noise of the loose bolts on the flywheel/flex plate is one of the scariest noises you will ever get out of an engine. Easily fixed though.
Regards
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By pegleg - 14 Years Ago
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Moz (9/14/2011)
frank that was when you got the new dizzy for me nearly 3 years ago now, ive checked all the other mains & big end bearings & there all still like new im asuming that because only 1/4 of the # 2 main is worn out is why there was no drop in hot oil pressure today i was thinking maybe i made them too tight i torqued the mains to 100 ft lbs maybe i should have only gone to 95. I would not think the extra 5lbs of torque did this. I would check the block there for cracks though. I'm begining to wonder if maybe there was something on the back of the bearing shell at that place where it got hot. did it score the crank?
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By Moz - 14 Years Ago
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frank theres no scoring on the crank at all even the bearing isnt scored just worn the journal is discolored though rick yes i agree one of the scariest noises to hear is a loose or broken flexplate they make so many different noises what threw me was it would only do it for about 2 minutes & with my near deafness i couldnt hear it very well in the end i only found it by accident
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By John Mummert - 14 Years Ago
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I agree with Frank. #2 is the most common place for the block to crack at the main web. The bearing bore could be pushing on the back of the bearing.
Although 5# torque shouldn't make much difference changing the torque value on a bearing bore is not a good idea. The bore will distort if the torque value is changed a significant amount. Even 10% could make a difference. When you have rods resized or a block line honed or bored you need to know what value the machinist used and assemble the engine with the same value.
Don't change rod bolts after the rods have been resized. You must resize rods if installing ARP rod bolts!
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