Level I & II Cylinder Heads for 1985-86 32 Valve Engines

     The 4 valve cylinder heads that Porsche equipped the first generation 5.0 4valve DOHC heads with were a direct development of the 935 4valve racing head designs. Although they are not ultimately as capable as the S4 and later heads, it has some unique design features that give it considerable potential.

     The 85-86 heads do have smaller ports on both the intake and exhaust. Although smaller, they are well shaped and can be very effectively modified through porting and the use of larger valves. A Level II 85-86 head will provide approximately the same power as a Level I S4 head. The higher velocity of airflow inside the 85-86 port will give better "cylinder filling", and there are many good racing engines that use that principle to their advantage.

     928 Developments Level I heads use stock valves. The valves will be reground and the seats will go through our standard 3-angle valve seat machining process. The intake and exhaust ports are then blended into the new seat contours.

     For the Level II heads, we install the larger valves from the S4 and port the valve bowls to accommodate the larger valves. The ports are also polished and enlarged at the valve bowls. We install high rpm spring sets, installed at an optimum height and pressure to tailor them to the selected performance camshaft set and prevent power loss from valve leakage due to erratic seating.

     Please refer to the camshaft section for the many different selections that are available. The camshafts available allow you many choices of tune and power. We will help you choose the best set for your power goals.

     Level I & II head assemblies come completely assembled, surfaced and ready to install. You will always receive the full benefit of our accumulated knowledge in all aspects of head preparation.


Level I 928 Cylinder Head Assemblies ($2100*)

• Valve seats contoured with radius departure cutters for optimum flow
• Intake bowls blended to new seat contours
• Intake Valves installed with new stem seals
• Exhaust valves installed with new stem seals
• High rpm spring package set at optimum heights
• Heads surfaced, cleaned & assembled

Exchange or we will rebuild your heads. Additional rebuilding services are extra, see below.


Level II Street/Racing Cylinder Head Assemblies ($3659.95*)

     928 Developments Level II heads use the larger S4 valves. These heads will deliver strong street and excellent race level performance. The carefully blended port bowls and polished port runners deliver significant increases in flow and a great performance value.

     Please refer to the camshaft section for the many different selections that are available. The camshafts available allow you many choices of tune and power. We will help you choose the best set for your power goals.

• Oversize S4 intake valve seats installed, high flow radius contour seats machined
• Intake ported for larger S4 valves, blended & polished
• S4 intake valves installed with new stem seals
• Blended & polished exhaust ports with high flow radius seats machined
• S4 exhaust valves installed with new stem seals
• High rpm spring package set at optimum heights
• Heads surfaced, cleaned & assembled

Cylinder Head Machining & Rebuilding Services

Install & size bronze alloy premium valve guides	$499.95/pr
Pressure test	$47.95/pr
Combustion chamber contouring and polishing	$245.95/pr
Ceramic coat combustion chambers	Call

* With undamaged & rebuildable exchange heads