I pulled my 381 out tonight and pulled the main caps off. I checked crankshaft end play and found .016. when i assembled the motor it had .005.
I pulled the rear main cap and sure enough the main bearing thrust surface was worn almost down. I had been having oil pressure problems, seemed like it was pumping the pan dry, which might or might not be related to my new problem. Engine has a total of about 50 miles on it.

here's what the engine is:
2 bolt main, arp studed
eagle cast 3.75 crank
eagle sir 6" rods
srp -16cc dish .020 pistons
standard clevite bearings, not the H's just normal what you'd get at Autozone.
Mellings M55HV oil pump
8qt pan with windage tray, extended pickup, about 3/8 from bottem of pan
TH400 Trans, 10" 3200 stall converter
i've read some posts about converter ballooning causing thrust on the crankshaft. Now the converter has about .250" of play when unbolted from the flex plate. This converter i've had for about 3 years with no problems ever on a very healthy 355 i had. I don't think its ballooning and I dont see one taking up the .250 play anyways.

any ideas on what might be causing my problems????

 

Does the converter slide easily all the way into the pilot of the crankshaft so the pads sit against the flexplate?

The thrust surface may also be suspect and not have a polished finish.

 

The troque converter is pre-loading the crank, there is a clearance problem there. Either your eagle crank is machined incorrectly on the back side, or your torque converter is not going all the way into the tranny.

 

The biggest problem is ya used the standard brgs. They are not up to the the beating. Get the "H" series and ya won't have the problem.Unless ya got one or more of the below problem's.
When ya bolt the bell housing up there should be 1/4-3/8 inch for the converter to slide back and forth between the trans pump and flex plate.
Does your converter have an anti balloon plate welded on to it?
There are two problems associated with thrust bearing failure-1 ballooning, 2 to much line pressure and trying to push the converter forward. Glide's have this problem real bad when ya get around 800+FWHP and 7000+RPM's and ya up the line pressure for the tranny.It doesn't care if it's a Ford or Chevy.
Did ya up your leave RPM's on the trans brake(if ya got one?)

EDIT: Did ya change your input shaft?

 

H's are pretty hard on a cast crank. Especially if things get a bit dirty as they can on a street car.

 

Na-- That's all I ever run. There is suppose to be oil between the brg and the crank and NO DIRT.....

 

This may sound strange, but check for poor, or non existent grounds.
I've only had 2 thrust problems over the years, and both were traced back to installations into older vehicles where the engine ground straps had poor connections to the chassis, or had broken and never been replaced.

One was an early 70's Corvette, and the other was a mid 70's Chevy pick-up. It's a fairly common issue with the Vettes, which is how I found out about it. I see in your sig that your vehicle is a '67 Pick-up......

I don't remember the technical explaination any more, but basically with poor/no engine to chassis grounds, the engine ground path goes to the rear main bearing(most surface area/ path of least resistance) through the rear of the crank -> flexplate -> converter -> trans input/ output shafts-> etc....

This grounding circuit attracts small metal particles which are common during initial break-in of a new engine, and they act like lapping compound between the rear portion of the crank & bearing thrust surfaces. This is why the damage occurs very early in the life of the engine..... usually less than 100 miles.

 

Since its deemed I don't help with information, and as such deemed untechnical as it were..I'll try to help...

The end play has been touched on as above.. but for your oil pressure probs..If bearing clearances are in check ,I'd take the HV( high volume) oil pump off and replace it with a HP ( high pressure) unit.. with a 8 quart pan and a HV pump you are just creating all kinds of windage with so much oil going to the top of the engine and could be sucking the pan dry or cavitating the pump from slosh/windage ...what goes up must come down as it were..who knows you may find a bit of power,however minute it may be...another thing is ,do you know how much clearance you have between the pickup and bottom of the pan??? does your pan have a windage tray, trap doors/ and or baffles??? what exactly is the oil pressure doing and what conditions? side note on the thrust issue,was that crank checked for straightness before it was installed?...reason being just because its new doesnt mean its right.
Bare with me if I dont answer timely,for I dont stay on here all day, I'm sure some others will chime in though if I don't..

 

I've seen tranny pumps do something similiar on electronic transmissions...extra ground straps is always a good thing...

 

Ya might check your bearing clearences on the rear main also. I like to run about .003 or +.001 more than the rest to insure the thrust DOES get oil.

 

Agreed, I do the same thing.

 

In my orignial post I stated everything i've checked.

converter moves freely forward and back when un bolted from the flex plate like it should. I can look up and see the hub of the converter enter the end of the crankshaft.

there is a thick ring on the front cover of the converter that has the ears going outward that are threaded that bolts up to the flex plate. that is the anti-ballooning plate i presume.

trans is pretty much stock, nothing too fancy, b&m kit with some over sized holes, no check *****, slightly higher pressure spring on the pressure regulator valve. i had this same trans behind my 6.0L for almost a year with no problems.

I did find that my Professional Products harmonic ballancer was rubbing on the Opti-Spark slightly, wore a slight groove in the opti cover, not into the yellow part of the opti. I installed a spacer ring between the hub of the ballancer and the crank timing sproket like the instructions said for a F-Body. The accessory belt lined up great.

i'm tearing the engine all the way down rechecking everything. Hopefully i'll find something. I dont see the ware on the opti causing the thrust bearing to go out. the plastic is a lot softer then the thrust bearing.

thanks for the reply's keep em coming.

 

What is slightly higher spring? What is the pressure now? Do ya have a trans brake?Are ya making more power now? Did ya change your input shaft? All of these questions are from now back to when ya ran the tranny before.
The opti thing didn't have anything to do with the thrust brg IMO.
The thick ring on the converter is the anti balloon plate.

 

transmission is untouched since before I had the 6.0L in my truck.

spring was from a "Mr. Shift" shift kit, nothing special.
no transbrake. stock input shaft, onlything aftermarket is a 36 element sprag and race. I dont know what line pressure is but this trans has been running without a hitch for over a year. I've had the converter for 3 years behind 4 different engines.

this motor only has about 50 miles on it maybe, never did a WOT pass or anything, mostly driving it to exhaust shop, home, and back to the shop to pull the engine after the oil pressure problem.

oil pressure was fine as long as i kept it under 3500 rpm. Any time above that oil pressure would dance around, never dropped to zero or anythign maybe from a steady 65lbs HOT it'd drop to 45 and jump around between. I never stayed in it when it was doing that, always let off.