Rod/Bearing Loss - Opinions

[Juddidiah]

For those of you who know what I've been through, I'm interested in your input. I am having a few more problems and I"m starting to look at other systems for the failures. Here are the problems in order;

Lost #7 Rod - Lasted ~440 miles - (tq'd rod bolts to stock, rather than aftermarket spec, my fault, that's fine)
Lost #7 Rod - Lasted ~120 miles - (The only thing I can think of is a potential over rev @6375rpm)
Lost #8 Bearing - Lasted ~110 miles - (Kept it below 5300, always had excellent oil pressure)

The only other systems I can think of to cause these failures is out of round tranny input shaft, but then i would expect #5 main to go.
Oiling system, but these failures are spread between 3 blocks, and 2 oil pumps.
First 2 losses were on the same crank, different crank/rods/pistons for the last one.

Is it semi-normal to lose a bearing on a motor that's sat for ~4 months w/o pressure (even though it was primed plenty before starting)?

[IROCnRoll]

What kind of evidence do you have that can be used to diagnose your problem. Need more input. Like did they just pound themselves to death or did you hear sreeching noises before it's failure, or did you hear the rods knocking sound. If they pounded themselves to death is there evidence to support excessive compression or a binding problem?. Are all rods equal in length?. Usually dirt (foriengn material) is the biggest factor in any bearing failure. If dirt is problem look for evidence of cuts in the bearing material. Also if you have a true oil cooler that cooler can be a culprit. Allowing and perpetuating for material to pass thorugh the engine. I use an old engine builders trick. I block off the oil pressure relief in the oil filter adapter. By doing this all engine oil is filtered always because the relief valve is no longer present. Check the other rod journals for out of round. Typically if one is they all are. Most machining irregularities are consistant. Just some starting points for us to diagnose what might be going wrong for you. I'm very sorry that this has happened to my friend. Anything I can do to help you let me know.

[DaBo_Z28]

Improper clearance  ,  dirt   , and  high volume pump with unresrticted galleys  (aka pumping all your oil to the top)  would be  causes of bearing failure as well 
as for sitting    that isnt a cause as my Rodeck would sit for 5 months or more during the winter after  a rebuild  and  be a ok for about 7 1/4 mile passes   (I used to change pinned rod bearings every week on the dragster as blowers take their toll on bearings and valve springs )  But  your prob sounds lack of oil to me   ,  be sure your not pumping  it all to the top starving the rod bearings ..  also  did you have new cam bearings installed ?  if so  are they in proper ,, as oil pressure  is dependant on cam bearings

[Juddidiah]

Thanks for the input, I"ll try to go through each item in order

did they just pound themselves to death or did you hear sreeching noises before it's failure, or did you hear the rods knocking sound.

1st time, there was a heck of a banging sound, due to the cap coming off the rod (lack of tq, my bad)
2nd time, there was no noticable banging, but the car was open headered. Rod bent at 90 degrees (as in the top was bent towards the front of the engine.)
3rd time, there was a noticable banging at mile 100, it was one present at 1100rpm plus, but i tore it down regardless

Rods the 1st and 2nd time were 6" Probe Lightweight I-beams, 3rd time was on stock LT1 rods

Dirt, there is no "dirt" persay, but there are more small metal shavings than I would expect. I'll all down for blocking the pressure relief valve. School me on that one jack.

1st and 2nd times the car had a high-pressure / stock-volume pump, 3rd time it was high-pressure/high-volume (but i put in an extra 1/2 quart to keep it wet)

Car has never had an oil cooler.

As for maching irregularities,
1st time the crank/rods bearing had ~2k miles on them.
2nd time all were machined and clearances were w/i spec. 
3rd time i never messed with the stock LT1 bearings

I really don't know how i would check to see if all of the oil is getting pumped to the top, what do you suggest?

1st time ~2k on bearings, but saw 2 different cams
2nd time, new installed cam bearings
3rd time, stock lt1 cam bearings
I've never seen oil pressure listed for a cams, where would i find more information on this subject?

THANKS FOR YOU HELP AND SUPPORT

[DaBo_Z28]

oil pressure isnt cam  its cam bearings   pump pumps oil into the crank  then up to galleys through the cam bearings then lifters then pushrods rockers and then drains back into pan   If the cam bearings arent correct (either installed wrong or  clearance problems ),    too much oil can go up starving the rod bearings .bearings can be lost from  that .

 some of the older 396 chevys had grooves in the cam  and bearings  and if you used a cam from a 396  in a 427  or visa versa  it wouldnt oil correctly  but  todays motors arent like that .    I was just  giving you something to look for as ive seen rod bearing failure  due to improper cam bearings  But  I bet your probs are something other than that

[Goody_Seven]

Have you checked clearences on the bearings?  Have you had the block checked since the first explosion?

[GeoffWhite]

From having seen the carnage from the first two motors it seems like an oiling problem. The last one was just 150k on the clock and the motor didn't like it!

[neat]

My God dude.

Normally I would never suggest something like this, but in your case...

It's insured.  Tow it somewhere where it'll never be found and report it stolen.  hide it in a storage unit and part it out, then report it stolen.  If your insurance fraud causes everyone's insurance on this site to go up, we'll all understand.

I've said it before, but it's worth repeating.  You are an absolute pillar of patience and tolerance.  Good luck man, drop me a line and let me know the whole scoop.

[IROCnRoll]

Dirt, there is no "dirt" persay, but there are more small metal shavings than I would expect. I'll all down for blocking the pressure relief valve. School me on that one jack.

The old engine builder trick I'm talking about is block off the oil filter adapter. That adapts the the filter to the block. In chevy's case they have a small pressure relief valve designed in to it. This valve is designed to relieve itself when the filter gets a little plugged. When this happens it lets all the metal shavings and any other debris thats present go through the oiling system and ruins anything the oil comes in contact with. The oil pump just pumps anything it doesn't know the difference. I pull out the little relief spring and fiber piece and get a 1/4 pipe tap and tap the hole so the 1/4 pipe plug fits almost flush +.06 above or so the filter spins on without hitting it (tight fit). I've used it for years.

Another idea, dirt in the pump pickup, pump itself.

Also since it's 7-8 rods that are going, that's the first place the filtered oil is hitting.

Have you cleaned all oil passages with a oil passage brush kit.