[DeTomaso] This ought to be fun...

[Asa Jay Laughton]

I'm no authority.

I say the bearing was slightly undersize, the crank was turned  
slightly undersize or the main bore was slightly oversize.  Any one of  
which would allow clearance of the bearing between the crank/main  
bore, thus allowing the bearing to walk out.

The only witness I call is the oil pressure.  Personally, I would  
think you should have been seeing -more- pressure from the get-go,  
especially if you were tapping it above the oil filter.  I would  
expect more like 75 psi hot at idle but I've been wrong on a lot of  
other things.  I base my personal testimony on tapping the oil  
pressure at the -back- of the block, using a stock oil pump and seeing  
86 psi.

The shop will of course deny it.  But how can anyone really know?  I  
doubt you'll ever know what was wrong.

To borrow from the wood-working trade:
- Mic it Twice, Plasti-gage it, and built it once.

Asa Jay

Good luck on the rebuild, I hope it all turns out.
Asa Jay

Quoting Kirby Schrader <kirby.schrader at gmail.com>:

> Personally recovering from major depression and lack of motivation on the
> Pantera front in Magnolia...
>
> The Space City guys already know about this and we've discussed it a lot,
> but for some reason, I'm in the mood to throw it out to the rest of the
> collective.
>
> My new 377 Cleveland engine build with less than 400 miles on it spun the
> front main bearing.
> I have never seen this happen, ever... and I've run the same combination of
> block, crankshaft, rods, etc. for years and beat the crap out of it with no
> problems.
> Daily driver, track events, etc.
>
> Facts for your consideration follow. I can get more detailed, but I think
> the following is enough to start you thinking.
>
> 1) Two bolt main iron block, lifter bores bushed, line bored, J&E pistons,
> Eagle rods, nodular iron crankshaft from Quella, Moroso restrictors (I
> spent a lot of money on this block!)
> 2) Iron 4V heads, new valves, springs, etc. etc. etc.
> 3) Comp Cams solid roller cam, lifters, pushrods, rockers
> 4) Symptoms were that my oil pressure started dropping gradually when I was
> driving home from the annual SCP pig roast. By the time I got to the last
> stoplight before my house, I was down to 10 psi hot at idle. Oil pressure
> is taken from the port just above the filter. You know it was less at the
> back of the engine.
> 5) There were no knocking, banging or otherwise nasty noises. Main bearing
> problems make distinctive noises. I know. Been there, done that. Got the
> scars. But I did not hear anything this time.
> 6) I pulled the pan and found bearing material.
> 7) Pulled the oil pump and it had obviously done some trash pumping.
> 8) All the other rod bearings and main bearings look just fine.
> 9) The front one had not only spun (when I pulled the cap, both had rotated
> by about 40 degrees), but one half was actually partially canted out of the
> web towards the front of the engine. I have pictures if you're desperate.
> 10) Nothing is blue or shows signs of getting hot.
> 11) The main cap is worn badly and has to be replaced.
> 12) The machinist thinks he can salvage the block with another line bore. I
> hope so...
> 13) The crankshaft journal needs turning, obviously, and can be saved.
> 14) The machine shop put the short block together, I assembled the rest
> 15) I had an Accusump plumbed into the back of the block where the stock
> oil sender usually resides. Accusump was set at 30psi.
>
> Proposed failure modes
> a) The main bearing was put in upside down - The machine shop is adamant
> that is not the case. 'Hell, no! No way!' was the response to that one...
> b) The crankshaft is bent - He's checking this week, but that would have
> been very apparent during assembly, so he believes strongly this is not the
> case.
> c) Not enough oil pressure - On start up and later, 65psi hot at rpm, 30psi
> hot at idle.
> d) It ran fine while I was tuning the EFI. Other than running rich
> initially and some issues with the ECU, I had no problems.
>
> Fortunately, no other damage occurred.
>
> So..... my questions....
>
> Why did it fail?
> What do I do to make sure it doesn't happen again?
> Why me?
>
> Who am I and why am I here?
> :-)
>
> Let the fun begin.
> Regards,
> Kirby
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-- 
Asa Jay Laughton - sent from somewhere other than home
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