Thread: 4tec throttle body bore out to 60mm

Be aware of the inlet tract lengths need a certain length at certain RPM's.

I am not a big fan of this simple method. You have to consider that the first cylinder will get a greater volume of air, easier than the others, as you get further from the Throttle Body.

Careful calculation may pay off here too.

Another thing is support for the finished item. There has to be a consideration for the stress applied to the manifold/head sealing surface, as this may change, and possibly leak too.