Replaced distributor oil seal and now wont start!!!

Hi, I changed the seal on the distributor as it was leaking on my 1983 gti, I marked the outside casing and the block and when i refitted it lined it all up as it was prior to removal,  Ran ok this morning, bit lumpy but not to bad. Then came to start her tonight and it she wont start, fuel fine, spark fine. Is there any way the timing can slip as really cant work out wat it would be,  

Can anyone help, Please!!!!!!!!!

I have run out of ideas.

Thanks alot

The obvious thing is you've shifted the timing. So, I'd be tempted to try set it up statically, at 0 degrees.