Choosing the Right Cylinder Heads For Your Set-up Reading this page and understanding the above terms will hopefully help lead you in the right direction. The best suggestion overall is to stay conservative. For example, a cylinder head with a large intake runner has no business on a low RPM street application (3000-4500 street drives and 6900-7000 top revs) This will result in a sizable torque loss, thus not meeting the needs of your intended purpose nor of the engine. Be realistic, choose the head that matches what you are doing and if you are selecting an assembled head, make sure the springs included match your camshaft selection. Intake Port Shape & Size - Cylinder heads have intake port runners where fuel and air flows through to get to the cylinder. On a 16 valve 4 cyl engine, each cylinder head has 4 intake and 4 exhaust ports. Each port matches up to an intake or exhaust valve. The size and shape of the intake ports affect the torque and horsepower curve. Larger ports can flow more. Plus, you usually try to match your intake port type on your cylinder head to an intake manifold with similarly shaped ports. Air and fuel flow through the intake into the intake ports on the heads. Restrictions, or misaligned ports, at this joint will alter the flow of air and fuel and may affect performance. One of the major concerns is that you get a good seal between the heads and intake manifold to avoid coolant leaks. Intake Runner Volume - A larger intake runner volume allows more air and fuel to flow through it. However, the larger "tunnel" will slow the velocity of gases moving through it. Smaller intake runners would speed up the flow of gases through the cylinder head and increase throttle response and torque. If you want the magic combination: A head with good flow and air velocity would give you the best of both worlds. The bigger your engine displacement, the larger your cylinder head intake runners generally need to be. The bigger your intake runners are, the higher the power band is pushed. If you want to build power for the street, huge intake runners will build big horsepower at NON-streetable RPMs. You're better off with smaller intake runners which help build power at lower RPM's. To which, my TPR Heads are made for application.. runner size, throat and bowls, valve size are all "Custom" you your needs. Exhaust Port Shape & Size - Exhaust port shape is less important than intake port shape. As long as your headers or exhaust manifolds are bigger than the port on the head, and the gasket seals well, the gas will exit as it should. Where intake runners on heads have to line up more precisely with the intake manifold for good flow must seal, the exhaust port shape is less critical. This is also where the TPR Ported "port-matched" intake comes in. Matched to the work done on YOUR TPR Ported Head. Intake Valves - Intake valves are typically larger than exhaust valves. 30.124 mm diameter intake valves are common r50/r53 engines. As you would expect, the larger the valve, the more air and fuel can be flowed through the valve (valve lift will also affect the volume of air/fuel flow). Intake valves are larger than exhaust valves because the piston is moving away from it,creating a vacuum to pull air and fuel into the cylinder. Pulling air and fuel in is not as efficient as pushing air out of the engine, as is the case with the exhaust stroke pushing exhaust gases out of the cylinder. Exhaust Valves - Exhaust valves are smaller than intake valves. 23.24mm diameter exhaust valves are on r50/53's. Like the intake valve, the larger it is the more it will flow. Cylinders are only so wide and you have to fit an intake and exhaust valve plus a spark plug in each cylinder. Or Having the huge valve stuffed in a small chamber isnt always the best Performance Design. There is a lot of structure support removed for the huge seats to be installed for the Huge Valves. With a lot of temperature changes and the material expanding and contraction with the heat, there can develop cracks in the chambers. This is just to add to the info you have already gained from different cylinder Heads. Just keep it simple and install the right bits to have a great and fast running car, yes? NOTE: a Racing car and engine build follow these guidelines also, however they are inclined to use and want high mid to topend power. Just saying................................. Thumper
TPR Ported Cylinder heads start at $1295.00 !! TPR Ported and Matched Intake manifolds start at: $275.00 Thanks Thumper Performance | The OTHER MINI Head! Thumper