72' 340 Drivers side HP manifold vs older HP manifold
In the picture (above) you can see a hump on the downward sweep of the late 340 (background) while the early 340 is virtually flat.
In the next 2 pic you can easily see that the early 340 is taller with respect to the exhaust ports:
In this last pic you can see that the early 340 rises higher (vertically) than the late 340:
Doesn't it depend on RPM??? From what I have read and experienced headers are great for performance at the higher RPMs (5500 and up). But at the lower RPMs a good set of 340 manifolds don't really hurt your engine performance more than 3-4 percent. As far as the difference in the early 340 VS the newer....they are virtually the same as far as flow is concerned. They are designed differently in that the early manifold rises higher in relation to the exhaust ports. The early manifold also seems to "hug" the engine a little tighter, for these reasons the early manifolds fit better on the early As than the older 340 manifolds. Unfortunately the early manifolds are usually more expensive and harder to find because there were very few made.
Treblig
In the picture (above) you can see a hump on the downward sweep of the late 340 (background) while the early 340 is virtually flat.
In the next 2 pic you can easily see that the early 340 is taller with respect to the exhaust ports:
In this last pic you can see that the early 340 rises higher (vertically) than the late 340:
Doesn't it depend on RPM??? From what I have read and experienced headers are great for performance at the higher RPMs (5500 and up). But at the lower RPMs a good set of 340 manifolds don't really hurt your engine performance more than 3-4 percent. As far as the difference in the early 340 VS the newer....they are virtually the same as far as flow is concerned. They are designed differently in that the early manifold rises higher in relation to the exhaust ports. The early manifold also seems to "hug" the engine a little tighter, for these reasons the early manifolds fit better on the early As than the older 340 manifolds. Unfortunately the early manifolds are usually more expensive and harder to find because there were very few made.
Treblig