He sent me pics of this so I can do it my new engine. Definitely worth doing. The other part of the Lutz mod is to increase the size of the pipe between the manifolds to allow greater flow rate, remove the plastic seals and sweat/braze the pipe into the manifolds.

 

The pipe change is Lutz stage II Warrjon, which I did not think was needed in my case. Below a pic of the mod to the front water manifolds. The foremost hole was reduced to 3 or 4 mm and the rear one to about 11 mm.


Ronbros: The remaining holes are plenty big enough to flow all the water the pump pushes through. In fact, as Warrjon indicates, the cross-sectional area of the water pipe between the manifold is the smallest part of the system. Norman kindly sent me his mathematical proof and demonstration of the areas concerned. If anyone wants it, I expect he would not object to me sending it on. TWR did something very similar to this mod when racing the XJS in the ETCC.
Greg

 

He is a very knowledgeable chap when it comes to getting power from a Jag V12, he built numerous V12's for hydroplane racing making 800+hp NA. In fact I bought my 6.0L V12 from him and have already spoken to him about doing the build.