Lots of info on all the different modifications. Has anyone tried to block off all 4 front outlets (into thermostat manifolds) ? Allowing all the flow of coolant to go to the back. Obviously less gph flow at high rpm, but I doubt I’ll go over 3/4000 rpm. Any specific data on the modifications?

Injectors : are the Mercedes 280 150 035 (400) the same as the Bosch 280 150 035 or the Lucas 73143 ?

 

I have done the stage one Lutz mod on my HE V12. The theory, which I consider I have demonstrated to be correct, is that coolant exiting the water pump into the block preferentially 'short circuits' through the front two holes leading into the front two water manifolds; therefore causing the rear of the engine to receive a relatively reduced flow of coolant.

The harder the engine is revved, the more this phenomenon increases, so it is a more important mod on harder used V12s. NOTE: the front two water manifold holes are NOT blocked off, they are reduced in diameter sufficiently to equalise flow to the heads at the front and the rear.

Norman Lutz has a number of stages, stage one is for road cars, and later stages 2 and 3 are for racing or higher output engines. It is noteable that the TWR XJS V12 racing engines in the 1980s, and many subsequent racing V12s had coolant exiting to the radiator from the rear of the heads, thus ensuring coolant flowed along the heads and out.

Here are some photos of the mod I did. A machine shop made up bungs with the correct Lutz sized holes in them that interference fitted into the OEM water manifold holes. For absolute certain this did help coolant flow to the rear of the engine, as the dash temp guage, the sender of which is on the front right water manifold, read a bit higher as soon as the mod was completed. This seems to me to be compelling evidence that preferential flow through the front water manifold had been reduced.



Before mod OEM sized holes from the block into the water manifold, through which coolant returns to the radiator


Lutz modded holes


Stage 1 mod hole sizes in the front water manifold are: Front hole: 1/8 inch (3mm), rear hole: 1/2 inch diameter (12mm)

Attached are Norman's notes which were sent to me.

 

Thank you Greg,
Have you ever experimented with one or 2 holes completely blocked off ? Easier to slide a thin sheet of Stainless in lieu of the gasket (sealed of course) and take some readings with probes (1 in the rear and one in the front)..
This will take several readings during several longer trips to have hard evidence. It makes total sense to at least do the Lutz modification.

 

Never tried blocked holes; but I do not recommend it. I think that with no exit from the block to the heads at the front you would creat a localised steam pocket at best, and a head//valve disaster at worst!
No reason not to slide in pieces of stainless with holes of the Lutz sizes in them though!