This thread has turned into a hive of activity. I figured it would get some people thinking. I should really give a bit more background on the build. This engine I am building is to full race specification. This is a very detailed build right down to every nut and bolt being replaced. It has all forged internals (crank/CP pistons/Pauter rods), custom Kent intake camshaft, big valves (inc sodium cooled exhaust valves), full port job (including oil and water passages), modified crankshaft (eyelets), custom designed pistons (in progress), big custom radiator, Mocal oil cooler setup, custom fabricated baffled sump with trap-door, custom ignition system and the list goes on (and on..). Everything is customized right down to the custom built pulley driving the supercharger. In addition I have a full data-logger setup incorporating wideband, charge temp pre and post supercharger, ex temp etc (all the usual suspects are also being logged).
There are two things however that must remain. The carb and intake manifold. I am not beyond making another manifold with internal velocity stacks and revised layout but it is not something that I am willing to do at this stage. The manifold redesign will come with my "next years" 2.0 build which will have a 16valve head, redesigned manifold, and possibly injection.
The headers are what I am working on at the moment. I figured rather than going to the usual crowd, I would see if anyone on GJ had encountered this issue in other engines and if they had played with the exhaust to improve the situation.
I am completely aware that changing the fueling (dual carb is not possible due to the historic supercharger) and manifold will solve the issue. #4 only runs lean on this engine with the supercharger setup, which is an
increasingly rare combination. These superchargers are becoming scarce. People do not go down the "authentic" path, they generally bolt a small snail to the engine and get great performance. I chose to go down what I call the "historic" with modern materials path.
As for these engines being unreliable or a bad design, there is nothing further from the truth. People regularly get 100hp per liter, with twin 45DCOEs out of these engines in N/A setups. These are extremely good flowing heads and are very robust engines in stock form. The Fiat name may not be highly regarded, but the Lampredi designed engines are. These were copied by many manufactures in the 70s. They are the basis of truly legendary cars including the Lancia 037, Lancia Delta S4, and the Lancia Delta Integrale.
Chris Harris has recently done a small segment on his ride in some of the Lancia Rally Legends at a Pirelli tyre launch. The engine I am building will eventually be much like the 037 which you can witness here:
If you would like to see what the engine is capable of, our crazy friends in Italy have a YouTube video of a running 1970's 1.8 liter Fiat engine (the same engine I am working with), (running injection) at 10,000 rpm putting out 250hp in N/A form:
Thanks to "meatness" and "phil u7c" for the ideas. It has given me some food for thought.
