Zipper’s Stage I WorkHorse Heads for Twin Cam® & Evolution® Engines

Add Torque and Power to any production Twin Cam® or Evolution® head with our WorkHorse blueprinting service. After cleaning and Step-Lock guide installation and fitment, proprietary seat and valve machining improves flow and ensures a positive seal by truing now heat-seasoned seats and removing typical production chatter that leads to leaks between the seat and valve. This process improves even new, low mileage heads on engines that are being upgraded with cams or big bore kits. Valves are upgraded to 7mm coated stainless 1.850” intakes and 1.610” exhausts with Viton seals, while new lightweight beehive valve springs with chrome-moly retainers and keys are set up for cam selection provided. Head gasket surfaces are skimmed to ensure absolute flatness. This Stage I head delivers a true, high quality “budget upgrade” for any engine, while updating 1984-2004 cylinder heads to modern, lightweight 7mm components.

Processing time

Once the cores arrive at Zipper’s they are unboxed, and inspected for shipping damage. Then we review your job order sheet and other related documentation. Job sheets that have not been finalized before your cores arrived will take additional time to sort thru before the job is put into production. Once finalized, the cores will be disassembled, serialized then move into production. Turn around (Process time) varies depending on the time of the season and how long it takes to get your job sheet finalized. Because of the dedicated skilled labor at Zippers and the vast amount of capital equipment we get the work completed with the highest standard of quality with one of the best turnaround time in the industry.

Work is performed on your supplied head cores.

For our standard production heads Shop Time is approximately 15 business days (during peak season allow for additional time).  The below options will require additional time to process:

• • Custom Modifications
  • Custom Finishes
  • Require Thermal coatings
  • Needing Additional Repairs
  • Or other Non-Standard Work

Exchange heads may be available if the condition of your cores qualifies. The process to determine the condition of your cores is to ship your cores to Zippers for inspection.

Exchange heads may be available if the condition of your cores qualifies. You can also purchase heads outright (without supplying a core set). We will supply clean, reconditioned factory castings for your application – add part #517-015 to your order.

International Customers – Import duties are not required when to shipping your castings for modification. Special low shipping rates are available for your cores; contact your sales representative for details.

Remove heads from engine, wash off oil and ship to Zipper’s as-is. Improper cleaning methods can actually do more harm than good; we suggest you allow us to properly prepare your heads for modification. Extreme care is taken during our preparation process to preserve component finishes. A small cleaning charge applies to heads sent in for modification.

*To ensure you enjoy a premium experience, Please fill out a Build Sheet/Job Order Sheet prior to completing an order on the website.
Click here for Zipper’s Build Sheet/Job Order Sheet

Not legal for sale or use in California on any pollution controlled motor vehicle.
Not legal for sale or use on any EPA pollution controlled motor vehicle.