AP Racing Engines Ltd

Great session on the dyno with GBS and their Mazda powered Zero.

Rolling road tuning is a popular service that many customers choose both pre and post IVA, helping ensure their Zero is running at its very best. Whilst this stunning Mazda powered Zero is with us for the IVA preparation and presentation service that we offer, we also presented the car for rolling road setup and testing as part of the process. Another important step in getting this Zero fully prepared and one step closer to being enjoyed on the road. @apracingengines #gbs #gbszero #kitcar #performance #setup

The simple reason for larger ports, valves and cams is to increase air flow. Any restriction at any point will diminish any other improvements as that becomes the limiting factor and in this case the restriction in air flow.
We have this cylinder head in for improvements as was ported elsewhere. It has +2mm valves and new valve seats.
We have re-cut the valve seats and increased the size of the I.D of the valve seat. This allows greater flow around and behind the valve ( taking advantage of the larger 35mm valve).
BUT as you can see it has left a large step where the original valve seat was, demonstrated the flow restriction.
This will of course be rectified before we rebuild it for our customer.
This is by no means a criticism, it is a message about where gains and losses can be found. So if you want to get the best out of a 35mm valve then don't put a 30mm hole / restriction in front of it.