Bought a d15b block the other day. Its the jdm version of a d15b7, which is pretty much a d15b2 (pm3 pistons). The block was supposeably rebuilt with new bearings and piston rings, but the old pistons were re used. As I'm cranking it with a ratchet, it takes a bit of force, but it rotates fully.
I have my d15b2 block out of my car and when I crank it, it spins freely without any effort at all!

These are both blocks without heads. I can see like black carbon on the sides of the pistons, I don't think the shop cleaned the pistons thoroughly and I feel like maybe there's carbon buildup that's not letting it turn as easily? I'd like to know If that will mess up anything.

 

an engine with the block honed and new rings installed is going to turn over harder than one that is worn out - won't spin freely

 

I agree with jlicrx. Also, do you have the spark plugs removed? I wouldn't worry about it too much.

 

I believe he stated these were both just blocks without heads

 

Oh ok so its normal then. Good to know. Thx

 

Oh, I didn't realize they were just blocks. I read block, but I was still thinking the head was attached.

If you have the head removed, you should be able to see the cylinder walls. I've seen carbon build up on cylinder walls from sitting for years and years. You'd probably be able to notice anything that is impeding the rotation.