After the sale of a beautiful blue green 1966 Ferrari 275 GT, we were asked by the new owner if we would put to use some of our in house technologies to increases engine power and reliability during the course of the total re-build of the SOHC Ferrari V-12 engine. The new owner wanted to both street drive and race the car at vintage events so he wanted a bit of extra usable power. Specifically they were interested in the types of modern scientific gains that we could find on our computer controlled flow bench in the general areas of air flow and engine breathing improvements. So the question was, could we improve the stock air flow of the intake tract which includes the air cleaners, carburetors, intake manifolds and the cylinder heads with little or no welding and increase the breathing and efficiency of the exhaust ports and exhaust headers as well. Lastly could we design and grind up a set of camshafts to match the air flow of the cylinder heads and the intended use of the engine and the car. This is by the way how camshafts should be designed and made. Not how most people and shops traditionally pick a camshaft which has more in common with a blue light sale at K-Mart than using proper engineering and designing for need and use. Proper engineering and design are how things are done here at Symbolic Motorcar Company. We improve the overall efficiency of engines here, how much and how far is always open for discussion and consideration.
We intended to construct a symbiotic engine where all of it s various components complement each other for the benefit of the whole.
My first step was to completely disassemble, clean and to fully inspect and measure all relevant components in the engine. A good deal of preparation is necessary to gain the proper information about the state of the engines condition. You must ascertain and record the level of wear on the internal components and the basic block and cylinder heads. Question to be answered are what is the current diameter of the crankshaft main and connecting rod journals? What is the piston to wall clearance, the piston ring end gaps and how far out of round and how much taper are in the cylinder bores? How worn are the cylinder heads? What is the wear on the valve stems and the valve guides? The extent of wear on the valve seats and the valve seats in the cylinder heads? What is the condition of the camshaft lobes and follower or buckets? All of this information must be known and recorded before you can start to order new replacement parts and to know how much machining and possible repair of the block, cylinder heads and components will need to be done.
Proper bore alignments and component fitment, balancing, the reduction of pumping and frictional losses within the engine. These are the basics of any engine and especially a high performance and or racing engine rebuild and blueprint. Power is made in the cylinder heads but the engine block is the foundation of the engine and one can not make efficient and reliable power with out a strong and proper foundation.
The cylinder heads, like the rest of the engine, were disassembled, cleaned, inspected and measured. The cleaned parts were noted and packaged for the future, assembly or simply to present upon completion. The valves and combustion chambers and port runners are cleaned and inspected. We wanted to perform a basic flow test the cylinder heads the object of these experiments is to get a base line reading from the intake and exhaust ports. The valves are installed in the head with soft test springs. I install the cylinder shrouding simulation test sleeve and then mount the cylinder head on to the flow bench. I need to know what the cylinder head air flow is in its current stock condition. While testing I will velocity map the port runners to find the speed and location of that particular speed of the charge in the ports. I will also try a few experiments concerning port and combustion chamber reshaping with clay. We will then use this information to map out a plan as to how I will modify the cylinder head for its intended usage, vintage racing.
I install one clean stock intake and one clean stock exhaust valve along with soft testing springs in to the combustion chamber and screw in a spark plug. I find the lexon tube that I will use to simulate the Ferrari 275 cylinders diameter. The lexon sleeve will also simulate any possible cylinder wall induced valve shrouding. This is done because I always want to test a cylinder head as close to its actual operating conditions as possible. I mount the cylinder head on the computer controlled flow bench and start finding some answers.
Temperature, humidity, barometric pressure, valve information, notes and other pertinent information is all stored in a separate file for each test. This allows me to go back and compare tests and keep track of what did and what did not work. Stock as received, ported and with various other modifications can all be noted, compared and categorized and placed it its very own information folder.
When everything is ready I run a base line test of an intake port opening the valve at fifty thousandth incremental steps through full valve travel, measuring the mass air flow through the port in cubic feet of air per minute, for the rest of the article this will be shortened to CFM. At each lift point I also take a number of velocity readings inside the port. This lets me know the speed of the air in various locations in the port. I also do other test to locate turbulence within the port as well.
After this base line testing is done, noted and stored in the computer, I remove the cylinder head from my flow bench and disassemble it. I now have my basic information and can now move on to test porting of this particular port. As the factory has already done some porting work I concentrate the majority of my efforts on straightening the port walls and re-shaping the bowl area. This is touchy work as due to the ports basic configuration and design, there is a limited amount of metal for me to work with. Because of these restrictions, how I want the port to be shaped and how it actually is shaped are currently two different things. We will see shortly if we can align the two. Flow benches and air flow testing in general did not come into general usage until the later 1970’s. So cylinder heads and ports were designed usually by what the engines design engineer felt was correct. The engine was designed, cast and built and if more power was required the camshafts and compression were fiddled with as is generally still the case today. Internal combustion engines are at their most basic, thermal dynamically controlled air pumps. As air is the working fluid it is the single most important element in engine power and in improving that power. You want more power? Improve your air charge intake in both quantity and quality, combustion efficiency, exhaust air flow and pumping efficiency.
After some port work in the same cylinder that we tested previously, I again assembled the test cylinder and readied the computer and bench for testing. The results were pleasing and good, the mass air flow or CFM and velocity were improved.
The intake manifolds do not automatically match up. It is very difficult to actually get them to match with out careful preparation and alignment procedures. Under normal circumstances and operation, as the rubber sealing o-ring deteriorates and wears, the manifolds will move around. If and when they shift, they will affect air charge flow to the inlet ports and combustion chambers.
Add the intake manifold and the good CFM reading from the cylinder head port dropped substantially. The intake manifold is a serious impediment to good air flow in the engine. As the heads do not flow that well in any case, this is not a good thing.