Headers for a A body
I'm been reading on how to improve the volumetric efficiency. Don't good heads help along with a good exhaust system, what about the intake manifold and air cleaner housing. I know that the car isn't home yet so I thought I would take this time to learn how to improve its overall performance. Improving the volumetric efficiency is a good idea even if it runs good? The first thing to do is to make sure it's safe to drive. Thanks everyone for your help
Those all comprise a "system" and need to match your desired end use. It really starts with the exhaust ports and manifolds or headers. Diameter, length and design are important. Long tube or shorties and 4 into 1 or tri y provide different tuning. Mazda for example, when designing their Skyactiv G engines found that a tri Y header contributed to lower cylinder temperatures at intake valve closing by about 60° and about 160° at the time of ignition. This contributes to detonation resistance. With conventional log manifolds the high pressure exhaust from a just opening exhaust valve gets pushed into the just closing exhaust of another cylinder. This causes the heating of the intake.
Tri Y separate the exhaust pulses contributing to improved low and midrange torque. 4 into 1 are long enough that the high pressure is not able to dilute the other cylinder. V8 exhaust works somewhat like a V6 with one big block cylinder on each bank causing the higher pressure pulse, which is what causes the distinctive V8 sound. Separating the two cylinders on each side that create that high pressure pulse is what tri Y headers do.
For proper tuning the diameter and length need to match cylinder volumn and expected RPM use.
When the exhaust valve opens there is about 70 to 120 PSI left in the cylinder that rushes at supersonic velocity out the barely open exhaust valve. This exhaust velocity combined with the weight is high energy. It roars down the pipe until it gets to an area of essentially atmospheric pressure at the collector. This positive pressure is then turned into a negative pressure that roars back up the pipe. When tuned properly about the 3rd or 4th time it gets to the exhaust valve, the valve should be almost closed and creates a negative pressure in the cylinder at the time the intake valve opens and the piston is still rising in the bore. This aids in initiating intake flow into the cylinder.
On the intake side we get pressure waves as the high velocity intake hits the closed intake valve. Remember that air has mass and moving air has energy, inertia. When it hits the closed or almost closed intake valve it builds pressure and sends a high pressure wave back up.the intake port. When it gets to the intake plenum the high pressure is converted to low pressure and travels back down the port. You do not want that low pressure arriving at the intake valve just as it begins to open. This causes reversion, sucking exhaust out the intake and fuel standoff over the carb.
For an air filter you are best with a closed filter housing with one or two hoses that bring in cool air from in front of the radiator support.
New vehicles that have those goofy "cylinders" off the side of the intake pipe are employing helmholz generators. These create high pressure pulses going into the plenum to aid the high pressure pulses going back to the intake valve just as it opens. For this a V8 functions like two 3 cylinders.
