Loud rattling on start-up

i have recently changed the fuel filler neck on my mk1 clipper auto and the car has sat for a few months. When i went to start it again it started fine but there is a really loud rattle coming from the engine?
any ideas.cheers

Starter motor bolts loose? I had one fall out.

Peter.

i dont think so goes on for a bit til the engine is warm. cheers

Loose tappets?
Mine sounds like there is a bag of nails under the bonnet until she is warm (really must check the clearences at some point… ops: )

is it doing much damage?  cheers for the help!!