The Yates family of cylinder heads were originally introduced to contend
with restrictor plate rules. The valve angles were changed (to 7.5 and
8.0 degrees with no side cant) to reduce piston valve relief depths and
permit higher ring packaging. Also, the combustion chamber shape was
revised for very high compression levels. The resulting head requires a
custom aftermarket rockershaft system, different pistons, valves, and
pushrods. The ports were also made small to allow custom porting and
require extensive porting to produce the desired flow numbers. When considering Yates heads, keep in mind the valve gear required to
finish the heads is very expensive. The custom Jessel rockershafts
and arms cost nearly as much as the bare heads. Out-the-door costs are
typically $4K+. The A3/B351/C302 heads are nicer in this regard since
they were designed to take standard, inexpensive, 4V parts.
Also, the small Yates combustion chambers (40 cc's) and are designed to
operate with custom pistons that are dished with a mirror image of the
combustion chamber. You can get Yates heads in a larger combustion
chamber size but the extra power they provide over the earlier
A3/B351/C302 heads is mainly in the chamber/piston design. Some racers
maintain the earlier SVO heads are still superior to the Yates (at least
the early versions) in non-restrictor plate applications.
Like the high port family, there are a variety of Yates heads (see
table below). The C3 and C3L will accept most Ford Motorsport Yates
intake manifolds and have the same raised exhaust port location.
The C3H Yates is has a higher intake port that requires a specific
intake manifold (available from FRPP and Edelbrock). Notes and variations
are listed below.
Yates SVO High Port Canted Valve Aluminum Cylinder Heads
--------------------------------------------------------
Part CC's Int Exh Int Exh Description
Number Port Port Vlv Vlv
Vol Vol Dia Dia
CC's CC's In In
M-6049-C3 40.0 210 119 2.1 1.6 high compression
M-6049-C3L 67.0 210 119 2.1 1.6 low compression
M-6049-C34 48.0 228 131 2.1 1.6 CNC ported and
Extrude-honed
M-6049-C34 48.0 221 131 2.1 1.6 same as C33 except
smaller intake port
M-6049-C35 67.0 210 119 2.1 1.6 Same as C3L but without
seats, guides, or
pushrod holes
M-6049-C3H 40.0 2.1 1.6 Allows for taller intake
intake port.
Yates Head Notes:
----------------
1. Require aftermarket shaft mounted rocker arm system
2. Staggered valves at 7.5 and 8.0 degree angles with no side cant
to reduce piston valve relief depths and permit higher ring package
3. Revised combustion chamber shape for higher compression
4. Phosporous bronze valve guides
5. Motorcraft AG-series spark plug
6. The C3H version is listed as a "High Port Yates" and has higher intake
ports requiring M-9424-W352 intake manifold and 5.45" long intake and
5.26" long exhaust valves. the intake manifold bolts perpendicular to
the cylinder head. Uses same rockershaft as C3L but requires longer
pushrods. Exhaust port is same as C3L.
Mustangsandmore Forums
posted 06-19-2002 07:45 PM
