Cambelt change now knocking

[kentiiboii]

Ok so we changed my cambelt today.
We made sure all 3 pulleys was timed up and bolts in holes.
Then after changing belt we took them out turned engine over and checked again they was timed, which they was.
Everything is tensioned up correct, but after starting for first time it ran with a very loud knocking noise. This noise was not there before we started the cam belt.

Any ideas what could be wrong?

Please help
Thanks in advance.