This is what I did and why.
So, deciding witch level you should go for when modifying an engine is important. Here I wanted to be able to make low rpm torque and also use original inlet manifolds, but also more flow than my 493 hp Gr.A engine, because I could use bigger valves on this job.
It is important to not open the upper part of the port to much as it is not there the flow restriction are, the biggest restriction are around the valveseat and up into the bowl.
And with to much cam and large ports you only loose airspeed and the possibility to take advantage of pulse tuning. You will never get above 100% volumetric efficiency. And also the smallest part of the port should not be bigger than the inlet manifold for a harmonic intake.
So, with this port I actually got more flow than my Gr.A heads and they are 32mm at the tightest throat. This is pretty good and will open for a broad use and possibility to make many different setups.
Inlet valve diameter 43mm
Exhaust valve diameter 35.5mm
Inlet port volume 90cc
Inlet port diameter at manifold face 36mm
Smallest diameter of inlet port 32mm
13mm lift capacity with seals installed
Valve guide material Colisbro
Valve material is manufactured from a one piece electrically upset 214N austenitic stainless steel forging, machined all over, with a Stellite 12 hard tip and a pulse plasma nitrided treatment for low friction and wear. Exhaust valve has additional Stellite 6 valveseat.
Compatible with std inlet manifolds (ports are not oversized).
Flow supports 600HP
Compatible with STD springs and retainers
Available with Mobeck springs and retainers to handle race cams up to 13mm lift and 40 kilo seat pressure.
Inlet flow max 196.5 CFM @10mm lift
Exhaust flow max 141 CFM at 12.5mm lift
Ole Martin Mobeck