I'm with JSpooner. If I already had a solid 400 foundation, I would develop that as far as it can go with much bigger reeds and carbs and ports.
if I was starting from scratch I would seriously consider a built Banshee with say a 421 CPI or Athena top end or larger and build a motor that could make way more HP that a ported 400.
If I had access to a 6 port TZ350D/E top end, I would sit down and work out target port-time areas and then work out if a 62mm bottom end would work and where would the ports need to end up.
Either way, I would start by working out HP targets and work through what I would have to do to achieve them before I started to sink tons of cash into the project. And if all budget becomes an issue as it does with all my projects, work out what you can do to a 400 to get as far as you need to go. Not a lot of point in sinking say $10 grand in a fully built banshee motor to win a $5 trophy and bragging rights.
if I was starting from scratch I would seriously consider a built Banshee with say a 421 CPI or Athena top end or larger and build a motor that could make way more HP that a ported 400.
If I had access to a 6 port TZ350D/E top end, I would sit down and work out target port-time areas and then work out if a 62mm bottom end would work and where would the ports need to end up.
Either way, I would start by working out HP targets and work through what I would have to do to achieve them before I started to sink tons of cash into the project. And if all budget becomes an issue as it does with all my projects, work out what you can do to a 400 to get as far as you need to go. Not a lot of point in sinking say $10 grand in a fully built banshee motor to win a $5 trophy and bragging rights.