I have the pistons and all installed. I used motor oil as lube, per the FSM. The crank rotated perfectly before the pistons and rods were installed. Now, it catches on something. When the pistons are at TDC/BDC, it rotates about 10 degrees with no resistance, but beyond that it takes a lot of effort, or just wont turn at all. I have wiped the cylinder walls with oil, and even poured oil onto the tops of the pistons and pushed it around to the edges to it will run down onto the rings. The block was bored .030 over and I got corresponding pistons and rings from the machine shop.
Help?

 

bttt?

 

did you get the crank cut for the 30 over

 

I had to get a new crank. (re-ground OEM). So, yes.

 

are the cylinder walls smooth? sounds like a crank problem did you measure the thicknesses before installing it

 

All bearings are properly aligned and locked in? Can you move each piston freely without the crank installed? No rods catching on the block anywhere? Just some thoughts...

 

Sounds like an identical problem I thought I had during my rebuild. I was able to turn the crank by hand before completing take down, but couldn't afterward.

https://www.yotatech.com/forums/f116...urning-246588/

 

I believe you have a bearing clearance issue. Loosen the caps on the pistons one by one till you can rotate it easily.

 

Did you use assembly lube or just motor oil? Did you plastigauge ALL bearings?

 

Just motor oil. Thats all the FSM said to do :\.. What other lube should I use? Like Petroleum Jelly?
Yes, I did plastigauge all the bearings. I will go back through and measure again, though.
Would it be reasonable to say the pistons are making kind of a suction thats preventing it from rotating?

 

You don't have the spark plugs in there do you? If so, yank them out. Its not uncommon for people to accidently swap the caps on the rods.

 

So:
New crank... assume you received new bearings too, right?

Were the cylinders align-bored/honed?

The whole binding after 10 degrees thing makes me think the cylinders were not bored/honed correctly causing the rings to "bind" as they move down the bore.

Picture an hourglass if you will.

 

my thought exactly. Straightedge should answer that question

 

Its just the block and pistons right now

I kind of have a thought they may have not been bored correctly. I took it to the most reputable and longest in business shop in town... so I would hope it was done correctly.

Everything is new- bearings, rods, pistons, rings. Crank is a re-ground OEM. Mine was noticeably bent, as were two of the rods.

 

I'd prefer to use a telescopng micrometer.
But a straight edge at the top of ring bore and laid aloing the cylinder wall would reveal problems just the same.

 

The only other issue I can imagine would be ovalled crank throws and wrong big-end bearings....

But then I only gave it 30 seconds...

 

Do you have the Rods installed in the same direction as when the were removed.

On some engines this will cause it to not rotate smooth.

Did the pistons go in smooth ?? a easy push with a wooden dowel with the rings giving a even resistance

If the block was bored incorrect it would have been very interesting to get the pistons in.

 

Plasti-gauged all The bearings again. All within spec.

It seems to rotate a little more smoothly, now. Maybe I had one or more of the bearing caps too tight. Following the FSM, and set my torque wrench correctly. There is still a slight catch when the cylinders are almost at TDC. Maybe I'm just paranoid... Video in a few.

 

http://s286.photobucket.com/albums/l...rent=001-3.mp4

 

looks to be turning freely, you may just be feeling the extra force on the crank from the piston. when at TDC the crank is vertical(parallel) to the piston and therefore your loosing leverage. when the crank is perpendicular to the piston you are creating force in the direction of travel so its easier. make sense?