O-Gauge Steamer
NAXJA Forum User
- Location
- Colorado Springs, Colorado
IMO...
A stroker motor requires a head with larger valves. A Forced Induction motor does not. It is a good idea, but with FI a goodly number of things change as you are no longer managing partial pressure (i.e. "vacuum").
My thoughts. There is no such thing as vacuum in an engine. There is partial pressure. You want vacuum? Go 300 miles straight up. If you are on the planet, however, you are dealing with partial pressures. Intakes and Heads are the crucial components in that management. The length and shape of the ports, the number of angles cut into the valve head, the floor of the port.
Floor? Yes. in most "ported" heads, the floor of the port is raised to reduce the turbulence which promotes the flow through the port. The Hesco (Patriot Performance) head has raised floors. Call Bernie and get the particulars. Just wish Hesco offered the big valve version...
With low pressure, any obstruction in the path will setup turbulance. The turbulence impeads flow which is why the 99+ intake is a better manifold than the log style. 90* bends are not the best idea for an intake. Swooping curves are. Air has mass and as such, inertia must be considered. Any mass wants to travel in a line. Hit a 90* bend and you get turbulence. What a log manifold has going for it is that is is a cheap and easy way to bolt on a carb/TB and they are a legacy from the dawn of Automotive time.
Plus... A vortex attempts to create in any tube that is flowing a gas. The center of the tube has a much higher velocity than near the walls. If the flow lasts long enough, time wise, the vortex forms.
In a positive pressure systems, obstructions are overcome by brute force. In partial pressure systems, elegance is required.
You know, I should get off the soap box here.
At least we do not have to take wall cling (fuel sticking to the intake manifold) into consideration with our injected motors like the carb'd engine designers do.
Marty, make some calls to your local Speed Shops to find where they get their head work done. It may turn out to be cost effective to have your head redone. All of these performance sellers (Hesco excluded) are working from cores which means that a competent performance shop can get you the results you are looking for.
Do the math here. A 4.6L 6 cylinder has the same cylinder volume as a 6.1L 8 cylinder engine. Look up the valve sizes on a GM LS3.
"The intake valve diameter has increased from 2.00 inches found in the LS2 to 2.16 inches for the LS3. Exhaust valve diameter has increased to 1.60 inches from 1.55 inches."
The beauty of the thing is that all engines are basically the same. With a given cylinder volume, the valves need to be close to the same sizes to get similar performance per cylinder. The number of cylinders really do not matter as we are talking flow dynamics of the ports. The intake manifold matters for NA vs FI but that is about it.
So a head with 2.0 intakes and 1.6 exhausts would be entirely suitable for a stroker or a FI engine. Altough the FI does not require it.
IMO.
A stroker motor requires a head with larger valves. A Forced Induction motor does not. It is a good idea, but with FI a goodly number of things change as you are no longer managing partial pressure (i.e. "vacuum").
My thoughts. There is no such thing as vacuum in an engine. There is partial pressure. You want vacuum? Go 300 miles straight up. If you are on the planet, however, you are dealing with partial pressures. Intakes and Heads are the crucial components in that management. The length and shape of the ports, the number of angles cut into the valve head, the floor of the port.
Floor? Yes. in most "ported" heads, the floor of the port is raised to reduce the turbulence which promotes the flow through the port. The Hesco (Patriot Performance) head has raised floors. Call Bernie and get the particulars. Just wish Hesco offered the big valve version...
With low pressure, any obstruction in the path will setup turbulance. The turbulence impeads flow which is why the 99+ intake is a better manifold than the log style. 90* bends are not the best idea for an intake. Swooping curves are. Air has mass and as such, inertia must be considered. Any mass wants to travel in a line. Hit a 90* bend and you get turbulence. What a log manifold has going for it is that is is a cheap and easy way to bolt on a carb/TB and they are a legacy from the dawn of Automotive time.
Plus... A vortex attempts to create in any tube that is flowing a gas. The center of the tube has a much higher velocity than near the walls. If the flow lasts long enough, time wise, the vortex forms.
In a positive pressure systems, obstructions are overcome by brute force. In partial pressure systems, elegance is required.
You know, I should get off the soap box here.
At least we do not have to take wall cling (fuel sticking to the intake manifold) into consideration with our injected motors like the carb'd engine designers do.
Marty, make some calls to your local Speed Shops to find where they get their head work done. It may turn out to be cost effective to have your head redone. All of these performance sellers (Hesco excluded) are working from cores which means that a competent performance shop can get you the results you are looking for.
Do the math here. A 4.6L 6 cylinder has the same cylinder volume as a 6.1L 8 cylinder engine. Look up the valve sizes on a GM LS3.
"The intake valve diameter has increased from 2.00 inches found in the LS2 to 2.16 inches for the LS3. Exhaust valve diameter has increased to 1.60 inches from 1.55 inches."
The beauty of the thing is that all engines are basically the same. With a given cylinder volume, the valves need to be close to the same sizes to get similar performance per cylinder. The number of cylinders really do not matter as we are talking flow dynamics of the ports. The intake manifold matters for NA vs FI but that is about it.
So a head with 2.0 intakes and 1.6 exhausts would be entirely suitable for a stroker or a FI engine. Altough the FI does not require it.
IMO.
