Raise The Roofs Of The Intake And Exhaust Ports

Removing the thermactor boss did raise the high lift numbers about 1 2 cfm after porting but then leveling the lateral.

Raise the roofs of the intake and exhaust ports.

It enters via the intake port as the piston rises into the crankcase and then is transferred to the combustion area via the transfer ports as the piston descends and the piston top uncovers the port opening to the cylinder. Two stroke port duration port timing basics. The port was a typical geometry for an si engine combined with a pent roof combustion chamber and four valves per cylinder. You mention exhaust vents shouldn t exceed intake vents in the roof for proper circulation.

Developing a port profile before flow benches the only way a head porter could tell if his work improved airflow was if the car ran faster on the track or the engine made more. After it is burned the exhaust gas exits via the exhaust port. Geometry setup the parametric intake port model was created in caeses and a set of seven parameters were selected for the optimization. It enters via the intake port as the piston rises into the crankcase and then is transferred to the combustion area via the transfer ports as the piston descends and the piston top uncovers the port opening to the cylinder.

All we care about is velocity and pressure. The roof raised in. A knowledgeable head porter can clean up the bowls raise the roofs of the intake and exhaust ports and probably find you an extra 30 to 40 horsepower for minimal cost. I have cut another exhaust port and still according to my flow tests i certainly cannot recommend raising the roof.

Do not raise the roof or the rings may drop below the top of the port and catch. That s why some port the intake by removing material from the bottom of the skirt of the piston. Be it the intake or exhaust the worst part of the port for air to negotiate is the short side turn. It s best to lower the port when needed.

Air gasoline enters the engine from the carburetor at a ratio close to 15 1. Intake timing is measured from the floor of the port. However with only two 1 ft x 2 ft gable roof vents i ll need an additional 7 sq ft of exhaust vents. With the way i ported this last exhaust port i lost 4 5 cfm when i tried raising the roof about 050.

Again you don t need to do this on your first saw. Nearly every single exhaust port today except for ford 302 5 0l and 351 heads are big enough.