Competition regulations that I need to adhere to state that I must use a single throttle body on the inlet and the manifold must be standard. I can get away with using a modified smallport manifold and I wondered how different the port spacing etc is compared to a blacktop 20v head ? Is the 20v head flow advantage over a smallport head worth the effort ?

you can house the itbs to single intake hopefully they wont notice lol

https://goo.gl/images/QCngtS

If not MRP has what your looking for they use it for turbo set up but you will need a custom throttle body and wiring

https://www.mrpltd.co.nz/product/4age-20v-plenum/

totta crolla wrote: Is the 20v head flow advantage over a smallport head worth the effort ?

On stock form the Blacktop head will easily outflow a stock smallport head. Flow @ 9mm lift is usually about 180cfm for a smallport, and about 190 cfm for a stock Blacktop. But total numbers are only part of the story... at lower lifts, the 20V EASILY outflows a 16V.

The real difference is in the exhaust, a stock 16V exhaust flows a max of 120cfm, where as the Blacktop is closer to 135.

slight porting on the intake side of a smallport quickly removes any intake advantage at full lift, but the lower lift advantage to Blacktop can't easily be overcome.

The exhaust side of a 16V needs a lot to flow similarly to a Blacktop.

As to port spacing... this is an adapter designed to mount the entire Toyota 20V ITB system to a smallport head.... port spacing should be dead on

Very interesting re. flow figures and it looks like it might be worth the effort.
I wonder what the chances are of the inlet manifold studs lining up are ?
The turbo plenums are very nice but they look 'modified' as far as the scrutineers are concerned.

biggest problem as I see it... the 20V manifold flange is angled, while the 16V manifold is not... likely need to do a bit of creative machining, or maybe make a small adapter......