Mopar thrust bearing failure

[BillK]

Originally Posted by devo340

Took it to our first race this season, lost #6 rod bearing.
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May be coincidence, started having problems after the trans was checked out.

I don't see how the trans would have caused a rod bearing issue. What did the thrust look like at that point ? Are you using the same bearings as before ? Same clearances ? Just curious.

[d miller]

I would think that BillK might be on to something here

Is this a new engine or has it run before without hurting the thrust bearing ?

The reason I ask is I had a problem with a thrust bearing in a 350 Chevy years ago. The block had been align honed and when they cut the cap they cut it crooked and it was tilting the thrust bearing just slightly. Took me a while to figure it out.

Did something change in your combination right before your thrust problem started ?

Just thinking out loud [/QUOTE]

[FED 387]

Bent crank-- trans crooked---convertor ballooning--- insufficient oil / lubrication---dowel pins not zeroed in ---- Fed387

[CMcAllister]

I agree the rod failure would be hard to pin on a trans issue. Not so with the thrust. 7 to 8 thou is a good number. Bump or pry the crank back and forth a few times before tightening the main cap and force the crank towards the front of the engine when torquing that cap down.

If the issue started after having the trans apart, I would have someone familiar with that unit in a race application look closely at it. Would be nice to run it on a trans dyno to verify pressures before putting it back in.

[S/ST 3040]

I wiped out the thrust bearing in my 340. After a lot of thought, I determined the failure came from
stacking the weight of the engine and transmission on the driveshaft at the hit. I had eliminated the
engine mounts and was utilizing an engine plate and OEM transmission mount to locate the engine.
After the crank repair, I added a fore and aft limiter. I've had harder launches since then and no sign
of thrust failure.


The first thing to identifying the culprit is asking, "What changed?"

[devo340]

One other thing was changed, weight of the car.
Was at 3640, now @ 3750.


Crank is internally balanced with Mallory metal.
This is why I elected to have it repaired.
To avoid the cost of rebalancing another crank.


Rob & Main bearings have been changed every time.


I am going to change out the crankshaft this time & have the line bore checked & corrected if need be.
Since I'm new to this type of racing, anyone want to recommend a crank shop?

[David Lee]

where are you located?

[devo340]

Originally Posted by David Lee

where are you located?

Oklahoma.

[David Lee]

Originally Posted by devo340

Oklahoma.

see if mike cotton is still in the area, if anyone would know it would be him

[dartman]

Make sure the hub is not bottoming out and pulling the flex plate to the converter.I had a simlair problem.had to put washers under the converter legs to pull it out of the crank.