All of the articles that I have read on heads and valves (which
generally
refer to Chev small and big block engines) talk about small valves being
the best for developing torque in the low rpm range - 2000 to 3000 rpm.
That's about the gist of it. Most of the small & big block truck
engines Chevy builds have smaller valves than comparable sized
performance engines. Visualize the engine as a vacuum pump, then
visualize the intake as a vacuum tank. Now open a hole in the tank
(intake valve), the bigger the hole, the lower the vacuum. The greater
the valve overlap (camshaft duration), the longer two intake valves
remain open at the same time. If I were to work hard at the heads on my
GMC it would be on the exhaust side of the event first, efficiency here
can always be improved. A little bowl blending and port matching would
be the extent of what I'd personally do on the intake sideand go with
Mondello's recommendation for a "short" RV style cam. These engines are
workhorses, the higher the operating vacuum, the better they will
perform in our application. My GMC goes into Ed Hanson's (the exhaust
GURU of the West Coast) this week for a 3" system with a rear mounted
muffler. If Gene wants, I'll shoot the process & send some pictures of
how it comes out. I know room in the rear for the muffler can be a
problem but this usually poses no problems for Ed.
Steve Ferguson
San Diego
generally
refer to Chev small and big block engines) talk about small valves being
the best for developing torque in the low rpm range - 2000 to 3000 rpm.
That's about the gist of it. Most of the small & big block truck
engines Chevy builds have smaller valves than comparable sized
performance engines. Visualize the engine as a vacuum pump, then
visualize the intake as a vacuum tank. Now open a hole in the tank
(intake valve), the bigger the hole, the lower the vacuum. The greater
the valve overlap (camshaft duration), the longer two intake valves
remain open at the same time. If I were to work hard at the heads on my
GMC it would be on the exhaust side of the event first, efficiency here
can always be improved. A little bowl blending and port matching would
be the extent of what I'd personally do on the intake sideand go with
Mondello's recommendation for a "short" RV style cam. These engines are
workhorses, the higher the operating vacuum, the better they will
perform in our application. My GMC goes into Ed Hanson's (the exhaust
GURU of the West Coast) this week for a 3" system with a rear mounted
muffler. If Gene wants, I'll shoot the process & send some pictures of
how it comes out. I know room in the rear for the muffler can be a
problem but this usually poses no problems for Ed.
Steve Ferguson
San Diego
