Rebuilt motor Too Tight?

[pett3227b]

Hi, I have partially rebuilt my 47' cub and have yet to put the motor back together completely. I have a new crankshaft and new bearings in and all the pistons with new rings in. I am wondering if I have put together a system that is too tight. I don't know either way if it is or isn't. Was wondering how I might could tell. I am about to put the flywheel back on. Thank-you

[tst]

did you check piston to cylinder wall clearance and set piston ring gap ? plastic gauge the bearing for correct clearance ?

[john2189]

When I put together an engine, after I tighten the mains for the crank, I turn the crank to make sure it is not to tight. And I do that for each piston and rod bearings, and every moving part. If you don’t do that, if you can’t turn the engine, you would have no idea where to start looking for what is tight.

[Eugene]

How do you know that the motor rebuild is to tight?

Lub everything during installation?

Install the flywheel. You should be able to easily turn the flywheel by hand.

I install a bolt in front of crankshaft. Install one part, crankshaft rotation checking for tightness.

[Bill V in Md]

If you are using plastiguage to check bearing clearances, be careful to remove all of the plastiguage material before re-assembling bearings. Otherwise, you will notice extra drag if you are trying to turn crankshaft by hand.

[outdoors4evr]

A freshly honed cylinder will feel like it is a bit difficult to turn. The break-in will help smooth out the bores.
Rings that have no end gap will likely break when they heat up.

[pett3227b]

I can move the flywheel by hand. It isn't real difficult to turn it but I wouldn't say that its real easy either. Should I continue with my installation or should I stop and go back to the main bearings and have them checked by a machinist? I didn't think it would be a problem since the Crankshaft was brand new and so were the bearings. If I take it back apart I would also check the piston rings and the rod bearings. Thank-you

[Eugene]

Back off the torque on one crankshaft cap. Then rotate the flywheel. Move on to second cap, then the third. If the amount of force needed to turn the flywheel frees up, that's the problem.

If not the main bearing caps, then the same with the rod bearing caps.

Not the main or rod bearings then you will need to pull the pistons.

Another thought. Are the bearing inserts correctly installed?

Bit later, another thought. Correct torque?

[Jim Becker]

I can move the flywheel by hand. It isn't real difficult to turn it but I wouldn't say that its real easy either. . . .

Since you aren't sure whether every clearance that should be checked was or not, going back and checking as explained by others may be appropriate. It would be for peace of mind if nothing else. However, I suspect you are chasing a non-problem.

[ricky racer]

I can move the flywheel by hand. It isn't real difficult to turn it but I wouldn't say that its real easy either. Should I continue with my installation or should I stop and go back to the main bearings and have them checked by a machinist? I didn't think it would be a problem since the Crankshaft was brand new and so were the bearings. If I take it back apart I would also check the piston rings and the rod bearings. Thank-you

If you haven't verified the main and rod bearing clearances with plastigauge, do that. You should never assume clearances are correct, verify it. Same with ring end gap, verify that the end gap is within spec. It sounds like a re-ring not a rebore but if I'm wrong and the cylinders were bored, check the clearance between the pistons and cylinder wall.
If all clearances check out within spec, you should be good to go.

[SamsFarm]

Maybe you did not use plastic gauge. (I dont)

But did you measure anything with precision measuring tools? (Micrometers, telescoping gauges, dial bore gauge, feeler gauges)

Is this your first engine build?

Friction of those piston rings running up and down in the cylinder walls makes for a little effort to turn things.

And if the head is on and plugs in, then you have to overcome compression too!

[Richard Goetze]

A quick check is to check side clearance on rods by moving them with your hand.They should move fairly easy .Likewise the crankshaft should move front to rear approx. 0.003 inch.

[pett3227b]

Okay, back to the cub. The rebuilt motor is definitely too tight. I have had the cylinders rebored and that has also added to the tightness. I am wondering how to check the clearance between the pistons and the cylinder walls? also what was spec for the ring end gaps? I also am wondering the process for using the plastigauge. My manual has a spec called the main and rod bearing diametral clearance. Is that the amount of clearance between the bearings and the Crankshaft? Thank-you

[Bill V in Md]

Okay, back to the cub. The rebuilt motor is definitely too tight. I have had the cylinders rebored and that has also added to the tightness. I am wondering how to check the clearance between the pistons and the cylinder walls? also what was spec for the ring end gaps? I also am wondering the process for using the plastigauge. My manual has a spec called the main and rod bearing diametral clearance. Is that the amount of clearance between the bearings and the Crankshaft? Thank-you

Ring End gap tolerance is 0.007" to 0.017".
Following is a link for a "How To use Plastiguage": http://farmallcub.com/phpBB2/viewtopic.php?f=141&t=56026

[Bill V in Md]

Suggest you refer to Blue Ribbon Engine Service manual GSS-1007, which includes instructions on rebuilding the engine. This manual tell how to measure piston wall clearance. It is available in the pdf manual section on this site.