Another blown up engine.
Click below to see the PhaseIII buildup... or continue reading to see why the engine melted again...
Click here to see pics of the new build up.
Well, I took the car to be dyno-tuned and....
Click here to see the car on the dyno
While we were dyno tuning the engine we discovered that my fuel system was not up to the task of supplying this engine under full boost. Unfortunately, we didn't find this out until we had done a couple of pulls up to 5,000 rpm and apparently that was all it took to do damage. Of course we backed off immediately, but by then the damage was already done. The injectors went static (100% duty cycle) and the engine leaned out. Too much heat built up and burned off the oil film protecting the sides of the pistons and resulted in heat damage to the number one and number eight pistons. We also had detonation, which smoked the number one spark plug.
Why did this happen? Well, when I supercharged this engine I was careful to select fuel injectors and a fuel pump that would be big enough to supply over 600 horsepower. The problem is that I totally ignored the rest of the fuel system, from the pickup tube in the tank all the way to fuel rails. What did I miss? The fuel lines themselves! When I restored this car I installed 3/8" steel fuel line from the tank to the carbs. 3/8" line is AN-6 and this size fuel line will support a maximum of 600 horsepower naturally aspirated. So it should have been big enough right? Wrong!
When you add forced induction to an engine it's BSFC will increase. What is BSFC? It stands for Brake Specific Fuel Consumption, and basically it is a measure of how much fuel an engine consumes to produce a given amount of power. Engines with lower BSFC are more efficient than engines with higher BSFC. Naturally aspirated engines are actually more efficient than forced induction engines. This means that if you supercharge or turbocharge your engine it will produce more total power but it will consume more fuel per horsepower produced. The difference is not gigantic but it is enough to make significant impact on the total fuel requirements of the engine. A forced induction engine will typically require 5 to 10 percent more fuel per horsepower produced than an otherwise identical naturally aspirated engine. This fuel consumption difference is only under full power conditions. Under normal driving conditions the two engines will have very similar BSFC, but when you stomp the pedal to the floor the supercharged engine will require more fuel.
So to make a long story short, my fuel lines were just barely big enough to support 600 horsepower, but not supercharged. With the supercharger I needed at least 1/2" or AN-8 fuel line. So what happened on the dyno is that my fuel lines simply could not flow enough volume when we went full power under boost and this is why the injectors went static and we leaned out.
We can rebuild it. We have the technology. Better, stronger, faster!
Of course, besides rebuilding the engine I was going to have to fix that undersized fuel system. I decided to go with a really big main fuel line. I would increase my main line size from 3/8" or AN-6 to 5/8" or AN-10. That's about the size of your average garden hose! That size line will support up to 1100 horsepower naturally aspirated, or 900 horsepower supercharged. I also decided to go with a real monster fuel pump. I chose the Aeromotive Eliminator. This fuel pump is insane, it will flow up to 130 gallons per hour at 45psi pressure! I would run my AN-10 main fuel line into a Y-block with two AN-8 or 1/2" fuel lines, one to feed each fuel rail. I would put my fuel pressure regulator after the fuel rails and have a single AN-8 return line back to the tank.
I decided to bore the block .030 over which will increase displacement from 493 to 500 cubic inches. For this new engine build up I've decided to go with a hydraulic roller cam. The new cam will have a bit more duration and 12 degrees of overlap. The increased overlap will bleed off a little cylinder pressure at low speeds so to compensate I'm going to order the new Ross racing pistons with a smaller 24cc dish to increase static compression ratio from 8.6 to 9.2. This time around I'm going to have the pistsons ceramic coated to give a little more protection against the increased combustion temperatures this supercharged engine can generate.
Click here to see pics of the new build up.