There was a pretty good thread on them a few months back. It started
off with me wondering why so many people seem to think they’re so
(as in the ‘chainsaw class’ comment below.) They’re not. I’ve used
one for years, and still have most of my original parts. (The
missing ones are marbles, so that’s not the lap’s fault.) I can’t
remember exactly what the headers were but search on my email
address, and ‘lap’ or ‘flat’ and you should get there.