Megaphone advice?

In reply to Purple Frog (Forum Supporter) :

I'll make mine. I have a 10 foot length of brass I've been looking for something to do with it. I'll roll it, weld it and then polish it like a band instrument  

Will the Jag engines take more duration?  I use the Cosworth L1 profile out of the BDA engines on my DOHC MG race motor which seems to carry a lot more timing than the Jags - a stroke thing?

L1 Camshaft
Valve timing 46/78/70/50. Duration 304 deg. Lift @ valve .410" (10.41mm)
Installation data:
Valve clearances (Cold) inlet .007" (0.18 mm)
Ex .008" (0.20mm)

Inlet valve fully open 106 deg. ATDC
 

On megaphones, I only used one for one season - I took a Norton Commando rear pipe (probably something you wouldn't want to trash today), gutted the baffles and cut it off where the diameter matched the pipe size I was using (2" or 2.125"?) 

 The next year they brought in dB meters and limits and I had to switch to an angled tip that I could rotate once I found out where the sound station was located that day.

The Norton megaphone definitely sounded nicer but I can't say that there was an obvious bhp pay off. 

In reply to wspohn :  
 I loved the sound of Norton motorcycles   the 441 Victor was my favorite  

I doubt there is power to be gained.  Rather the sound.   I'm seeking more of a scream then a bellow.   That and since it's going to be made from  brass and brought to a High shine. 
It will be a distraction.  More of a band instrument then a race car thing.  
      I also intend to drip Castor Bean oil into the exhaust. Have you ever smelled Castor bean oil like the old Castrol R?  To me it's the smell of old British sports cars. 
   Back in the 50's castor bean oil provided better lubrication than traditional motor oil. The only Flaw it had was the deposits it left in the combustion chamber were really hard to remove and it could foul the spark plugs easily.  
 I figure if I drip it into  the exhaust pipes I'll get the smell without the mess. 
  OK not all my time needs to be spent making the car faster. Racing is about having fun too!