That little-known (and now almost-defunct) Blackpool sports car maker had a crack at a (full-size) V12, the first by a British company outside of F1 for decades. They fabricated the prototype block from steel. Calculations suggested it'd be good for 650bhp in road form and 800+ when track-tuned; allegedly when they dyno'd it they found something like 780 and once the tweaks were done it made over 1000bhp!
Some of this is possibly urban legend put about by TVR themselves but the version that eventually did make it to the track in the Cerbera V12 doesn't hang around... it was destined to go into the Speed12 road car but even though a couple of people (including Liam and the other guy from band Prodigy) put money down, Peter Wheeler pulled the plug as he thought it was too risky to sell that much power in a car without driver aids...
Yeah, he built it himself, he always does weird and wonderful engines, his last one was a W12 built out of 3 bike cylinder heads, 1400 supercharged bike engine, and he did a 2.0L V12 before that, along with a few screaming V/I6's to boot.
Ah ha I scrolled down, and here's his own translation
v-12 engine with compressed air injection,hand made using taditional methods:12 cm3 of displacement,the diameter of the cyllinder is 11,3 mm,the stroke of the pistons 10mm,it works with only 0,1kg/cm2.Is constructed with stainless steel,aluminum and bronze.Patelo dedicate this engine to his grandchildren:Sara,Carmen,Jose and Pablo.This engine is for education,exhibitons,etc.,that is the reason to work with compressed air, to avoid contamination.He has made the plans and all parts, except the screws.The engine is not for sale.Thanks to everybody for the comments and sorry for my bad English.