NISSAN RB26 RACE HEADS
Here is some before and after on this RB26 head race head. Nissan designed a really good port. We just felt the need to make it better by filling in a few dead areas in the port.
As for the surface finish, because this is going to be living at high RPM we have finished with a light texture of 60g to allow minimal boundary layer thickness. We need to remember the higher the rpm the greater the boundary layer thickness relative to the Ra finish of the ports surface.
This has had a full weld up and reshape of the floor to fix the dead area where the divide meets the floor and also a full weld up and reshape of the injector area. This has allowed as to remove both dead spots in the port.
The divider is no longer vertical and hitting the incoming air wave all at once. It's now twice the length of before and is radial profiled to allow separation over a greater distance, which reduces drag coefficient of the port.
There are quite a few options when building a custom race head. One of the more important points that tend to get overlooked is valve size. All too often oversize valves are put in heads without any understanding of CSA and air speed or what the engine will be used for and in what RPM band. And as we have shown this can sause you to loose Horsepower rather make power. Especially when looking at Horsepower to Boost pressure Ratios. So at Bain Racing before we build a race head we analyze your setup and work out what is optimal for your setup.
A lot of people tend to think big horsepower needs big valves. This is simply not true. rather RPM, VE factor and cubic capacity are what will indicate what size will work best.