neil33

BD144. Main bearing change w/out Crank removal?

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So I have another question for you guys......

Is it possible to change the main bearing shells without removing the crank from the engine?   My thinking is that if I remove all bearing caps I might be able to drop the crank enough to push the upper shells out and push the new ones in.

Pics below of one of the main bearings and big  end bearings, which appear to be less worn.

My investigation in the low oil pressure on my restoration led me to drop the sump, only to find the oil pump gauze pretty well blocked with sludge. After changing the oil pump with a used (but known good) pump there is a small improvement in oil pressure but I feel the next step is the change the main and big end bearings but at this stage don't really want to remove the crank to have it reground.

Advice appreciated.....

IMG_20171022_172600923.jpg

IMG_20171022_174253084.jpg

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Yes you can, there is a tool made (or you can make your own) that slips into the oil hole, it protrudes enough that when you turn the crank it pushes the bearing shell out. Before  changing the bearings check the clearance with pasti-gauge, if the clearance is within spec I would leave them.

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I used a modified brass cotter pin to roll out and in new shells in my C-135. I only removed one cap at a time but had them all loosened.

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Years back the little tool/pin used to come in the field service "roll in" bearing kits

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Use chip man's advise and loosen the other caps to roll the bearings out and in, will make it a lot easier.  Don't take them all off at once.  In order to plasti gauge the new inserts you will need to add a thin spacer, feeler gauge works if insert is installed, under one of the caps to force the crankshaft up to get a good reading on  your plasti gauge of the others.  Have fun looking up with oil dripping down.

Dennis

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Great advise guys....Thank you!

 I will have a crack at this at the weekend, I presume the new shells will roll in quite easily if all the caps are loosened, or maybe I can use the same cotter pin method to roll them on. . Will also get some plastigague on order once I find the correct size.

I'll let you know how it goes.......

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Odds are very good that the cam bearings are the source of oil pressure loss and those bearings removal / replace require the block to be on the work bench.

 

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Well a bit of an update....the good news is that the cotter pin method does work well, but the bad news is that all of the main bearing journals have corrosion marks on them so It looks like I now have a much bigger job in dismantling the entire engine to change the crank (based on the quotes I have had, its cheaper to replace than regrind), and on oleman's advice, I'll change the camshaft bearings too.

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