I am doing a whole engine rebuild:

1. new pistons, rings, bearings
2. new camshaft
3. redone block and head, both have been decked resurfaced etc.
4. New sprockets and chain
5. new lifters and rods
6. new oil pan, oil pump

when I turn the crankshaft it works perfectly fine, however this is the problem. When I put the head on all of the sudden it becomes extremely difficult to turn. Or another way to say is that the pistons all of the sudden don’t want to move. It seems like it is sucking a lot of air or something. It shouldn’t be this hard to turn.

is it possible that my head is bad? It really shouldn’t be since I’ve had it for about 6+ months and it got redone by a machine shop.

Is it possible that the crank isn’t positioned right?

I really don’t know what it could be. I appreciate any help on this!

 

Do you have spark plugs in the head? If so, that is normal. If you don’t have the plugs in, you have other issues.

 

oh really.. I’ll have to take them out then. However if the issue still persist then it’s a head problem?

 

I highly doubt it’s a head issue. It would have to be warped like crazy. Again, if you have the spark plugs in, it should be a complete pain to turn over. That’s actually a good thing.

 

i took the spark plugs out and it cranked just fine! Would you know why this happens? And when I put the engine back in I should have nothing to worry about?

 

Yeah, it turns easier with the plugs out because there's no compression.

As far as "nothing to worry about " given how things have gone so far all bets are off.
If you and the machine shop did everything perfectly it will be fine. If not,who knows.

 

with the head on, spark plugs in, rockers and pushrods not installed, you have every cylinder on "compression stroke" as you turn the crank each cylinder is compressing the air between the top of the piston and the head. With no way to relieve the pressure, the turning of the crank becomes harder....removing the spark plugs the engine is now venting air through the "compression stroke" and the motor turns over easier because of no resistance or pressure.