C-175 crankshaft

Loafersglory · Dec 21, 2009

I am installing a crankshaft in a C-175 engine. The crank has been reground and the bearings sized for crank. Specs are “max main clearance .0055” and “main run clearance .0011 - .0041”. Using plastigage and torqueing the oiled bolts to specs, clearance on all three bearings is .003 - .004. After the plastigage has been removed and the bolts retorqued I cannot turn the crank by hand. If I torque only bearings 2 & 3 and leave 1 loose I can turn crank by hand. Bearing 1 has the least clearance of all .004. Will I have a problem with this? Will the crank/bearings need to “wear in”?

Anonymous-0 · Dec 21, 2009

Any debris under the bearings? I had one get a small spec of dirt get under the center main, it would not spin.

If the front or rear main cap gets swapped, it wont spin. tangs on the bearings sit together so if one is turned backwards it wont spin. It should spin freely,,,, also check all of your bearing part numbers,, make sure they are all the same part number and size.

Take the crank back out,,,
remove the bearings,
reinstall the main caps,,

then get you a diegrinder,,,,, I set up a slotted shaft in my grinder that I can wrap 320 with, and polish the block where the bearings sit.
If its dirty, it should loosen up and be where you need it.
If not, you might need to take it to a shop and have the mains in the block checked for out of round,,,
but doubtful that is possible. Hope this helps. ChadS

teddy52food · Dec 21, 2009

Chads has good advice. Also make sure the crank is ground the full length of the bearing. Loosen the cap a little at a time until you can turn it over . Then take it apart & see if there is a tight (drag) spot on a bearing. If there is you will have to find out why. Don't put the engine back together as the bearing has to be free. No breaking in. If you have the crank out ,torque the caps without the bearings. Get a good straight edge & try to see if the block is straight. It may need line boring. Please let us know what you find.

Owen Aaland · Dec 21, 2009

(quoted from post at 20:50:38 12/21/09) ........
If the front or rear main cap gets swapped, it wont spin. tangs on the bearings sit together so if one is turned backwards it wont spin. It should spin freely,,,, also check all of your bearing part numbers,, make sure they are all the same part number and size. .......... ChadS

On most IH engines the main bearing tabs DO NOT go together on the same side. Make sure you have the cap on the correct way before you do anything irreversible like polishing the bore.

El Toro · Dec 22, 2009

Your main bearing caps should have a number on them and that number faces toward the cam shaft.
Look on the back side of the new insert bearings
to see if they have the correct undersize marking
on them for the reground shaft. If they reground the shaft to .020" undersize your inserts should have that on the back side of the inserts. If they are the correct bearings and your caps are on correct and you can't rotate the crankshaft by hand I would take the block & shaft back to your machine shop. I think you should be able to rotate that crank with only .002" clearance on the bearings. Hal

Anonymous-0 · Dec 22, 2009

The tabs sit together on the same side on all H-450 gas engines. 6cyls too.

What I mentioned is not anything that will hurt it, providing thats whats wrong. ChadS

Loafersglory · Dec 24, 2009

Thanks to all. The best advice I got was "check the basics and then check again". There is no better answer than common sense. I was looking for a major problem when all it was was a burr on #1 bearing cap. Ten seconds with a file and I was all set. Merry Christmass to all who have "been there and done that" AR

C-175 crankshaft

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