So I recently got a 69 RR with an overcammed 440, since I knew nothing about the engine setup. The plan was to remove and identify cam, and pick cam accordingly. As I was doing that I noticed excessive crankshaft endplay. So I pulled the engine out. Sure enough there was massive clearance at the thrust bearing. Pulled the main cap off and realized that the crank was substantially worn at the thrust journal. My question is. I believe I have a good crank to drop in, but the crank in the engine is balanced as well as the rods. Are they balanced to each other or independently? Do I just install the replacement crank or should it be balanced?, does it have to get balanced with the rods/pistons? Familiar with engines but not familiar enough with the balancing aspect. It’s been a while for me. Thanks for any advice!!

You need a full rebuild at this point. All that bearing material has circulated thru the oiling system so it all needs to be taken apart, cleaned, inspected, etc. The machine shop can verify which crank to use and handle the balancing.

Yes I was aware of the full rebuild due to debris I was just trying to avoid the run-on posts LOL. When you say the machine shop can verify which crank to use, do you mean that the thrust journal may be repairable? I would hope to avoid messing with the balancing it has. Thanks for the response!

The thrust surface can be welded and remachined. I've had this done in the past w/ no issues.
Or you can have your other crank checked out and balanced for those rods & pistons.

Thanks for the info, and of course I need to now check if something is pushing/pulling the crank forward. I've seen where a swapped T56 was not fitting into the pilot busing correctly and caused similar damage but only into the bearing that time. I need to verify the converter isn't pushing into the back of the crank. Could a misaligned timing gear pull the crank forward? Sounds crazy but my mind is analyzing all posibilities. I haven't check for any misalignment yet.

Routine job for a crankshaft shop. If the engine was installed in front of an auto trans, problems in the pump can cause full line pressure to enter the converter and cause constant pressure against the thrust bearing.

It is backed by a 727, Any suggestions as to how I could verify full line pressure to the converter?

I am noticing some grinding on the inside of the crank snout so I am suspecting the converter may have been tight against it and whoever installed it just took a dremel type tool to get some clearance. Unverified but that's a possibility.

Price out getting the crank welded, straightened and ground versus just getting the other crank balanced. I know the first job would be a moderate PITA, and balancing it would be pretty simple, unless it's some stupid parts combination that would need heavy metal added, which isn't common. S/F....Ken M

Someone might have put the wrong bearing in there, the size changed in 70s

Make sure the converter is not ballooned.

A restriction in the transmission cooler lines, cooler, or fittings can force the converter forward damaging the crank thrust. Issues within the transmission pump and/or valve body may be a factor as well. As already said, crank may be repaired and reused for minimal costs.

Using an incorrect balancer and/or flexplate can cause it too. I had an externally balanced 6 pack rod 440 that had a neutral balance flexplate and converter on it...ate up the thrust bearing and had over .060" endplay. Put a new #3 main bearing in and got the correct flexplate...no more issues.