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

The Ultimate 4V Cylinder Heads - Stage 4 CNC Porting Program, Oversize Valve Seats, Bronze Valve Guides, Competition 5 Angle Valve Job, +1mm Oversize Manley BeadLoc Valves, PAC RPM Series Valve Springs, Viton Stem Seals, Surfacing and Assembly
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MHS 4.6L / 5.4L 4V Stage 4 Competition 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.

This is the Ultimate Porting Package for 4V Cylinder Heads. Stage 3 Porting Program, Oversized Valve Seats, Bronze Valve Guides, Competition 5 Angle Valve Job, Hand Blended Bowls to Valve Seats, Manley +1mm BeadLoc Groove Valves, PAC RPM Series Springs, Surfacing and Professional Assembly
These Cylinder Heads are capable of making well over 1500 RWHP and turning more than 9000 RPM... RELIABLY!

Stage 4 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. Valve Seats are then removed, The heads are then ran through our Stage 4 CNC Porting / Chamber Program and then to our Seat and Guide area where our custom Bronze Guides are installed and honed to size. We then machine the heads over the oversized hardened valve seats, install them and hand blend them before the valve job. After the Seats have been installed we perform our Trick Competition 5 Angle Valve Job and finish blending the bowls if needed, The Heads are then surfaced on our CBN / PCD Surfacer and Assembled with our Viton Valve Stem Seals, Manley +1mm Oversize BeadLoc Single Groove Valves and our PAC Stage 3 Valve Springs and Chromoly Retainers. Heads will also be assembled with new USA Made Brass Freeze Plugs and New Oil Gallery Plugs. 

03/04 Cobra Guys and Gals - No need to worry here. Since both Intake and Exhaust Seats are being replaced with oversized ones, there is no additional charge. 

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 usually 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.  


  • Disassembly and Cleaning of all Parts
  • Bead Blasting of Ports and Chambers
  • Full Competition CNC Porting w/ Hand Blending Bowls to Seats
  • MHS Bronze Valve Guides - Honed to Size
  • Oversized Hardened Valve Seats 
  • Competition 5 Angle Intake / Radius Exhaust Valve Job 
  • Manley +1mm Oversize BeadLoc Groove Valves and Locks  
  • PAC Stage 3 or Series Springs and 4130 Chrome Moly Retainers 
  • CBN Surfacing 
  • New Viton Valve Stem Seals 
  • New Brass Freeze Plugs and Oil Gallery Plugs 
  • Assembly

Options and Upgrades: 

  • Upgrade to Titanium Retainers - Recommended for 8000+ RPM
  • Upgrade to Inconel Exhaust Valves - Recommended for 35+lbs of Boost
  • Upgrade to MoldStar 90 Valve Seats - Better than Beryllium and the absolute best valve seat material for competition use. 
  • Add Copper O-Rings to Cylinder Head Deck for MLS Head Gaskets - Helps with Head Gasket retention. Suggested for applications making 1300+ HP. 

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.
  • W24.0000” x H12.0000” x L12.0000”
  • Free Shipping!

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