hey hilly, heres a website to help with your calculations. i have got an exel file that does the same thing but better, but it's on my other computer.

http://bigboyzheadporting.com/TwinCamComp.htm

Baz

Hey Oz, i got pipes made up by a guy useing a computer program ages ago, they were stepped and turned out bloody long, it was on an old shovel 98" stroker i had, when i road it bike felt a lot slower, so i went back told the guy shorten them up to 32" he was winging do you want power or looks, but shortened them up and the bike ran a lot stronger, also the baffle he used even though it looked like a big diamiter caused the gas's to spin and shound like an old Vee dub, just removing that got another good increase. i've always found that about 32" tappered end muff no baffle 1 3/4" worked good for me. seems to hold the TQ up longer than 2 into 1 too.

But Gonzo up in QLD uses a computer program and he always made pipes for Mark Wackers bikes and they fly, should try a set of Gonzo's but think you have to go up have them made on the bike. think he feeds all the info like valve size so on into his pc program, has worked with HD's a lot over the years. but for me i think too much education in Harley pipe design does nothing for all out HP the simple 32" tappered end muff 1 3/4" always works good for me i've got the ceramic coated but not sure if that helps.

cheers