crooked crank

Ed Saniewski

Ed Saniewski

Well-known member
The engine that came with mt 29 ccpu was rebuilt about 12 years ago. The truck was also ( so called ) restored at the same time, and very very poorly done. I removed the engine from the truck last year and discovered there were many shims on one side of the bell housing where it connects to the fly wheel housing. When I took the oil pan off to clean out 10 year old oil, I noticed that the crank shaft was not straight. The babbitt looked as if it had been bored out on an angle. When I reassembled the flywheel housing and the flywheel, I measured a .03 hundredth of an inch on one side. My question is should I continue to reassemble the engine? If I put the transmission on, this will throw the center line of the drive train off more. How much leeway is there with something like this? Am I better off pulling the engine apart and having the block rebabbitted?Thanks for any help, I hope this makes sense
 
The flywheel housing is usually aligned with the crankshaft flange first. It would be interesting to see how many shimms approximately the thickness of the gasket to get the flywheel housing to align with the crankshaft. After that the flywheel is checked for wobble or out of round with the housing. If all that could be done sucessfully, the transmission should be in good alignment with the engine/flywheel assembly. If it takes too many shimms you might have to think about getting the engine lower end repaired correctly. I would think the rod bearings would be in a bind if the crank journals weren't properly align bored/honed plus the problems of keeping oil in the pan that would be associated with a misalignment there.

Kerby

PS: .006" is considered the maximum "out of alignment" you can have between the crankshaft flange and the flywheel housing and .005" is the maximum flywheel wobble you can get away with.
 
Ed Saniewski said:
The engine that came with mt 29 ccpu was rebuilt about 12 years ago. The truck was also ( so called ) restored at the same time, and very very poorly done. I removed the engine from the truck last year and discovered there were many shims on one side of the bell housing where it connects to the fly wheel housing. When I took the oil pan off to clean out 10 year old oil, I noticed that the crank shaft was not straight. The babbitt looked as if it had been bored out on an angle. When I reassembled the flywheel housing and the flywheel, I measured a .03 hundredth of an inch on one side. My question is should I continue to reassemble the engine? If I put the transmission on, this will throw the center line of the drive train off more. How much leeway is there with something like this? Am I better off pulling the engine apart and having the block rebabbitted?Thanks for any help, I hope this makes sense
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The flywheel houseing is probably warped. Most are warped at least a little and cracked.
 
Hi Ed, I'm not clear on what you mean about the "crankshaft not being straight". Do you mean that it was not line-bored in parallell to the line of the engine block, but at an angle? If you were able to detect this, then yes, you must absolutely correct it as there are so many geometries being violated that the engine and drivetrain will not be able to compensate for them. The damage that will result in relatively short order will exceed the cost of correcting the fault at the present time. Good Luck with this!
 
I have never heard of shims between the flywheel housing and the bell housing. Sounds like someone was doing a cheap and dirty correction. If the crankshaft is not parallel to the block, nothing else is ever going to fit right as Chris says. Take it to a machinist with the proper tools and check the line bore. The key to a proper line bore is the initial index guide. Guys on this forum with more knowledge and experience than I can tell you more about that. If it is off, you will need a new babbitt job to correct it
 
I am going to remove the flywheel housing today and try another, but I am pretty sure the line bore was not parallel to the line of the engine. I kind of figured this might be a problem. Thanks every on , Ed Saniewski
 
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