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4.6L / 5.4L 4V Stage 3 CNC Porting Package

Stage 3 CNC Porting Program, Hand Blended Bowl to Seat, Bronze Valve Guides, Performance Valve Job, Manley Stainless Steel Valves, Stage 2 PAC Valve Springs and Retainers, Surfacing and Assembly
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MHS 4.6L / 5.4L 4V Stage 3 CNC Porting Package - This is for 03/04 Cobra / Mach 1 Heads only.  For GT500 Heads, please see our GT500 specific packages. We do NOT port "B" Heads or 99/01 Cobra Heads.
Short and Sweet Description: This Package includes our Stage 3 CNC Porting Program with Hand Blended Bowls to Seats, Bronze Guides,Performance Valve Job, Manley Stainless Valves, MHS / PAC Stage 2 Valve Springs and Retainers, Viton Stem Seals, Surfacing and Assembly

Stage 3 CNC Porting Package - Not so short description
We start by disassembling the heads, thoroughly inspecting them for any possible damage, removing all oil galley plugs and freeze plugs, removing the old valve guides, deep cleaning them and bead blasting the ports and chambers to remove any additional carbon deposits. The heads are then ran through our Stage 3 CNC Porting Program and then to our Seat and Guide area where our custom Bronze Guides are installed and honed to size. We then perform our Performance Valve Job (4 Angle Intake, 3 Angle / Radius Exhaust) and then blend the bowls to the valve seats. The Heads are then surfaced on our CBN / PCD Surfacer and Assembled with our Viton Valve Stem Seals Manley Stainless Steel Valves and PAC Stage 2 Valve Springs and 4130 Chrome Moly Retainers. We have multiple Valve Spring / Retainer options as an upgrade. Heads will also be assembled with new USA Made Brass Freeze Plugs and New Oil Gallery Plugs. 

03/04 Cobra Guys and Gals - Please be aware that the 03/04 Cobra, Mach 1 and Aviator Heads all have less than adequate Exhaust Valve Seat press fit. We are not sure why, nearly every set we have seen in the last 3 years has had at least one loose exhaust seat. We will not take any chances in sending a set of heads out that we are not 100% confident in. We haven't had any Valve Seats fall out and we aren't planning on it! With that being said, we will have to replace the Exhaust Seats with a better alloy and fitment. The cost of this is an additional $320.00 and includes the price of the Valve Seats. 

Spark Plug Inserts: We can convert any 4 thread spark plug boss to a full 9 thread using the Timesert Aluminum Inserts. This can also repair any lightly damaged or pulled out threads. If your heads have already had a plug insert repair done, it is already too big for this option.  

Cylinder Head Cores: We have the 2004 Cobra DB 9 Thread Casting Cores on the shelf. These cores are available in addition to the cylinder head package. These cores have been thoroughly inspected and have perfect cam bores. This can save you the time and hassle of looking for good cores, as well as save you the cost of the in-bound freight. Please note if you do select our cores, you will still need to select the exhaust seat upgrade. 

  • Disassembly and Cleaning of all Parts
  • Bead Blasting of Ports and Chambers 
  • MHS Bronze Valve Guides - Honed to Size
  • Performance Valve Job (4 Angle Intake, 3 Angle / Radius Exhaust)
  • MHS Standard Size Stainless Steel Valves
  • MHS / PAC Stage 2 Valve Springs 
  • MHS 4130 Chrome Moly Retainers 
  • CBN Surfacing 
  • New Viton Valve Stem Seals 
  • New Brass Freeze Plugs and Oil Gallery Plugs 
  • Assembly

SHIPPING- After your order is received, we will ship out a set of Cylinder Head Boxes to you with Pre-Paid Return Labels, all the proper packaging and packaging instructions to ensure your heads arrive safely. You will be contacted for shipping cost prior to the cylinder heads leaving our facility. 


  • Modular Head Shop
  • New


Shipping Information

  • Item Requires Shipping
  • 100.0 lbs.
  • Free Shipping!

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