Engine wont turn over

Hi could someone advise me as I'm getting stick of this problem.

So I have checked everything out and I'm sure I'm getting right but apparently I'm not. My engine was seized and I've managed to free it up and it now turns over by hand freely. I put the head back on and I've done the timing and suddenly I can't turn the engine at all.

It's like it just binds up and the only way to free it is to loosen the cams. I'm stuck in a frustrating loop and I can't see what's going wrong. Could someone please advise me. It will end up in a scrap heap at this rate.

Thanks in advance.

 

What machine do you have?

 

Xj550

 

https://www.xjcd.org/book/export/html/505

Do you have this. Double check your cam timing. Chapter 3 engine overhaul.

 

https://www.xjcd.org/node/613

 

You need to isolate the issue. Remove plugs, disconnect the cam sprockets by removing the bolts. Then try carefully turning the cams - don't be surprised if you find a valve comes against a piston. If either cam does not move or is really tight you likely have the caps wrong. They are numbered...
In an ideal world the pistons should be half way up/down the bores to do this but if you cannot move the engine it makes this difficult. Tread carefully, don't force anything.

 

When you say the engine was seized, what's the history? Seized how? Engines don't seize without scoring something - pistons, crank bearings, - cam bearings?
More info needed, it's a 2 way thing..