Try this....
Hi Alan,
Welcome aboard.
Here are a few thoughts to try and help:
1 - Comet Engine
Try Russ at VinParts - they advertise on this site - his father recently had a box of bits Comet that might still be for sale.
2 - Value ? Mmmmmm
Pretty much they are worth what someone is prepared to pay for them.
Some recent ones I have actually seen sold:
Comet box of bits - all there for the full bike but needed total bottom up restoration with no idea what mechanical work (expensive) needed on the engine - sold for £5000 in April of this year.
Nice Comet - at auction they seem to go for about £7 for a complete and sometimes running bike at the low end to beyond £10 for a nice one. Like everything at auction, all it takes is two people who want it and the achieved price sets a new record. Problem then that lots of other people then believe that that is what one is "worth" - both unfortunate and potentially wrong.
3 - Engine Only
Seen a couple go on ebay over the last year - about £3.5 to £4.5K from memory - you might be able to so an ebay search of past items to find them.
My best advice is to join the VOC, £28 for a year, you get the super MPH magazine monthly where members advertise to buy and sell, occasionally you'll see a Comet engine. There are lots of them under people's benches where they have used the cycle parts for the basis of a Twin. Being a member of the club may put you in touch with someone who'll let you have one.
You'll also get the benefit of full access to this Forum site - including all the members only sections which incorporates the buying and selling section - so you could place your advert and also watch iin case someone posts one for sale. If you're serious about a Comet engine then surely the £28 is a worthwhile investment.
4 - Performance
I am no expert but you can bore them out to 600cc plus - there are many knowledgeable sections members in the VOC who have a lot of experience in race tuning the Comet, again a good reason to join. There is a specific Grey Flash section and they may be able to help you with more specific detail.
5 - Join the club - another reason
Not everyone in the world is a decent type whether in the club or not, joining the club gives you access to the machine register and researcher too, they can check numbers for you - you may not be particularly interested in getting an engine with matching crankcase halves and associated parts that were on the bike when new - but it has been known for people to "clone" Vincent engines and it may be unhelpful for you to spend a load of money on the engine only to find it is a duplicate and you get in a mess with the DVLA, the Police or the Classic race scene - some circuits are now checking numbers and more - even worse would be to buy a stolen engine, they are out there. Joining the club and using the services available won't prevent you from falling into these traps, but they might just help you avoid them.
If we can help with anything else - just ask.
Regards
Stuart
Hi Alan , welcome to our world !!! Can't help with your queries though , outside my experience , although I will say I haven't seen many Comet engines for sale anywhere , even fleabay !!!