User Guide

24—Dyno2000 Advanced Engine Simulation
help you determine the appropriate selections for your application.
Low Performance Cylinder Heads—There are three “Low Performance” cylinder
head selections listed at the top of the Cylinder Head menu. Each of these choices
is intended to model cylinder heads that have unusually small ports and valves
relative to engine displacement. Heads of this type were often designed for low-
speed, economy applications, with little concern for high-speed performance. Early
260 and 289 smallblock Ford and to a lessor degree early smallblock Chevy castings
fall into this category. These choices use the lowest discharge coefficient of all the
head configurations listed in the menu. Minimum port cross-sectional areas are 85%
of the valve areas or somewhat smaller and, if Auto Calculate Valve Size has been
selected, relatively small (compared to the bore diameter) intake and exhaust valve
diameters will be used.
The first low-performance choice models an unmodified production casting. The
second “Low Performance/Pocket Porting” choice adds minor porting work performed
below the valve seat and in the “bowl” area under the valve head. The port runners
are not modified. The final choice “Low Performance/Ported, Large Valves” incorpo-
rates the same modifications plus slightly larger intake and exhaust valves and some
modest work in the port runners. Auto-calculate valve size increases vary, but they
are always scaled to a size that will install in production castings without extensive
modifications.
The low-performance choices have some ability to model flathead (L-head & H-
head) and hybrid (F-head) engines. While the ports in these engines are even more
restrictive, by selecting Low-Performance and manually entering the exact valve
sizes, the simulation will, at least, give you an approximate power output usable to
evaluate changes in cam timing, induction flow, and other components.
Typical Wedge Cylinder Heads
The “Wedge Cylinder head”
menu choices model cylinder
heads that have ports and
valves sized with performance
in mind, like the heads on this
LT1 smallblock Chevy.
Cylinder Head Menu