Hammer Performance - for All Your Harley Davidson XL Sportster and Big Twin Performance Needs
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Pictures of Harley Davidson and Buell Performance Cylinder Heads


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CNC HEAD PORTING

For Sportster & Buell


Quick Links:

We Specialize in Preparing Sportster and Buell Heads

An XL1200R Head Being Ported by CNC

We have many years of experience preparing XL/Buell heads for both street and race applications. We've run literally thousands of XL heads through our proprietary process over the years! Click here to read all the details on our advanced CNC process.


We offer four levels of CNC porting service for Sportster & Buell Heads:


The Impact service treats your heads to our exclusive and proven 4-Axis CNC port treatment, followed by hand finishing, bronze manganese valve guides, a custom radius valve job, sizing of the chambers to achieve your desired compression ratio, and decking your heads to get a perfectly flat gasket surface.


The Smash service adds to that our premium quality high flow oversized stainless steel valves and a spring/retainer pack that allows more lift and more aggressive cam lobe profiles.


The Crush service is a special service that takes advantage of the large valve seats in certain XL heads to utilize extra large 1.900" stainless steel intake valves, while keeping costs down.


The Sledge service adds even bigger valves (with a seat change if needed), plus a port configuration custom sized to your specific engine and intended usage, as well as any optional special services such as angled squish bands or external head drains.


Do you need cylinder head castings as well? Hammer Performance can set you up. We offer brand new factory high performance heads at a competitive price. These heads make the best foundation for our porting service.


The pictures below show some of the steps that ALL levels of head porting service include.


Cutting the Deck on a Harley Cylinder Head Performing a Valve Job on a Harley Davidson Cylinder Head

Tech Tips:


Impact - $550:

Make a Big Impact on your Bike's Performance!

The Impact level is a perfect match for bolt-in cams and street type exhaust systems, giving a wide powerband and a smooth running engine, with the reliability and longevity you demand.

CNC Ported 2004-2006 Harley Davidson XL1200 Heads

We start by stripping down your heads, cleaning them thoroughly, and inspecting them for any defects.


We then run them through our exclusive 4-Axis CNC porting process which sizes and shapes the ports for maximum torque over a wide rpm range. The CNC machine is also used to open up the seat diameters and rough in the valve job. A hand finishing process is then applied to the ports and bowls which basically compensates for variances in castings.


Next, new bronze manganese guides are carefully pressed-in and sized followed by an exclusive radius valve job on the seats, paying special attention to the target stem protrusion and resultant spring installed height. We reface your valves, lap them into the seats, and despite the incredible repeatability of the CNC process, we flow test every head as a quality check.


Your heads are then decked for a perfectly flat gasket surface and to size the chamber back to factory specs.


Finally, we test your springs for proper seat pressure and travel, and assemble the heads with new high-temperature viton stem seals.


The end result is a set of heads that are better-than-new. They will tremendously outperform the stock heads and can take much better advantage of your performance cams and exhaust system.


We've had numerous customers break 100rwhp using this level of head prep on their Sportster or Buell. It's a truly a superb performance value.


Impact Head Service
Impact Head Porting Service - Pair

Impact Head Service Options
Front Mount Bracket
(to Adapt XB/04-Up XL1200 heads to 86-03 Models)
$14
Intake Manifold Flanges (Pair)
for 2007-Up Sportster Heads
$12.30
Machine Squish Band for Angle Dome Pistons (Pair) $80

Specify Angle:

Machine for Second Spark Plug (Pair) $100
Machine for External Head Drains (Pair) $140
Machine, Drill, Tap Breather Bolt Holes on XB Heads (Pair) $60

Measuring the Chamber Volume on a Harley Davidson Cylinder Head Flow Testing a Harley Davidson Cylinder Head

Smash - from $750:

If you're looking to Smash your competition, this service is for you!

Harley Davidson XL883 Sportster Cylinder Heads CNC Ported

The Smash level is a definite step up the performance ladder, for riders who want a HOT street or entry level race bike.


All of the same services as the Impact level are applied to the heads: thorough cleaning and inspection, 4-Axis CNC porting, new bronze manganese guides, our exclusive competition valve job, decking, flow testing and assembly with new viton valve stem seals.


But there are a couple of key differences. Number one, we include a set of our oversized high flowing stainless steel valves (see the table below for the valve sizes you'll get). Naturally, we set up your ports and seats to match these large valves. The end result is substantially more flow than can be achieved with the stock valves.


Second, we pair these new valves with a brand new high lift performance spring pack. The exact spring pack we'll use is selected specifically for your application (cam grind and maximum rpm).


For moderate lift cams (up to .550") and rpm ranges we recommend the factory 04-up beehive spring pack with our Striker 7mm stem valves. This ultra-light arrangement is also very economical, because the springs and related hardware are all mass produced pieces. We can fit this updated 7mm hardware to any of the various XL heads.


High Performance Valves, Springs, Retainers, Locks, and Guides for a Harley Davidson Cylinder Head

For higher rpms and cams up to .600" lift, our new Striker Beehive spring pack with Striker 7mm Stem valves is the hot ticket. This is a super premium PAC alloy spring pack that's been heat treated, stress relieved, multi-stage shot-peened, and nitrided for superior durability. It comes complete with titanium retainers. Again, this package is available for any of the various XL heads.


For 883 heads, we offer two different 7mm valve options. Our standard offering is a set of KPMI 1.715" intake and 1.480" valves that takes your valve sizes up to the same valve sizes as the 1988-2003 XL1200 heads. These work well with dish conversion pistons.


For even more power out of your 883 heads, and to take advantage of higher lifts, we offer special 1.760" intake and 1.530" exhaust valves in the 7mm stems. These are the largest valve sizes that will fit in the stock seats. Their installation provides extra valve to valve and valve to piston clearance, both of which are helpful for cams with higher amounts of overlap. They generally must be used with flat top pistons, as they cause the chamber size to be larger. This is an incredibly well performing setup, it literally makes a set of 883 heads capable of supporting 100+horsepower:


HAMMER PERFORMANCE 100 horsepower Sportster 1250 dyno sheet


This dyno sheet is from a 2007 XL883 equipped with our $750 SMASH service to it's original 883 heads, a flat top 1250 kit, a set of our IMPACT 560 cams, an Air Hammer air cleaner, a Torque Hammer exhaust system, and tuned with TTS Mastertune. The lifters, pushrods, rockers, valve springs, throttle body, coil, etc are all factory stock pieces, and the compression ratio is only 10.5:1 which makes it very pump-gas friendly. This is a very cost-effective way to get your 883 to 100 horsepower!


With late model XL1200 or Buell XB heads, the SMASH level makes them capable of supporting north of 105rwhp, The SMASH service also make a great set of street heads for 88/90 cubic inch motors.


Cam lifts above .600" need our heavy duty 5/16" stem Sledge Hammer valves and a top quality Hammer Performance dual spring pack. We stock spring packs all the way up to .700 lift and can go beyond that if needed. This arrangement includes 10 degree locks and titanium retainers.


Tech Tip: Don't order your heads with more or less spring than you need, instead match it carefully to your application. More spring pressure than necessary causes extra wear and less than necessary causes valve float or worse.


Smash Head Service
Smash Head Porting Service - Pair
With 7mm Stainless Valves and OEM Beehive Springs (for cams up to .550" lift)

Cams and Pistons You'll Use, Target CR:

Smash Head Porting Service - Pair
With 7mm Stainless Valves, Striker PAC Alloy Beehive Springs, and Ti Retainers (for cams up to .600" lift)

Cams and Pistons You'll Use, Target CR:

Smash Head Porting Service - Pair
With Heavy Duty 5/16" Stainless Valves, High Lift Springs, Ti Retainers (for cams up to .700 lift)

Cams and Pistons You'll Use, Target CR:


Smash Head Service Options
Front Mount Bracket
(to Adapt XB/04-Up XL1200 heads to 86-03 Models)
$14
Intake Manifold Flanges (Pair)
for 2007-Up Sportster Heads
$12.30
Machine Squish Band for Angle Dome Pistons (Pair) $80

Specify Angle:

Machine for Second Spark Plug (Pair) $100
Machine for External Head Drains (Pair) $140
Machine, Drill, Tap Breather Bolt Holes on XB Heads (Pair) $60

Smash Head Service Valve Sizes
Head TypeStock Intake
Valve Size
Smash Intake
Valve Size
Stock Exhaust
Valve Size
Smash Exhaust
Valve Size
883 (dished conversion pistons)1.580"1.715"1.350"1.480"
883 (flat top pistons)1.580"1.760"1.350"1.530"
88-03 XL12001.715"1.760"1.480"1.530"
04-up XL12001.810"1.850"1.575"1.615"
Thunderstorm1.810"1.850"1.575"1.615"
XB1.810"1.850"1.575"1.615"

Harley Davidson XL1200 Sportster Cylinder Heads CNC Ported



Crush - $850:

Maximum Power at Minimum Cost!

The Crush level of head preparation was designed by HAMMER PERFORMANCE to let you take advantage of the large seats found in certain XL heads, giving you a maximum performance Harley Davidson XL1200R Sportster Cylinder Heads CNC Ported set of heads at reasonable cost. If you have a set of Thunderstorm, XB, or 2004-present XL1200 heads, and you're going to be using cams of above .550 lift, you can take advantage of this special service.


We will prepare your heads and fit them with whopping 1.900" intake valves instead of the standard 1.850" as shown above for the Smash level of porting. These larger valves really help the flow at higher lifts. You have your choice of either 7mm Striker valves with our premium PACalloy beehive springs and Ti retainers (good for up to .600 lift), or our 5/16" stem Sledge Hammer valves with Sledge Hammer premium dual springs and Ti retainers that can support either .650" or .700" of lift. Bronze manganese valve guides and viton valve stem seals are standard as well.


So how much power can a set of CRUSH heads support? Take a look at this chart for an example:


HAMMER PERFORMANCE 111 horsepower Sportster 1250 dyno sheet


This dyno sheet is from a 2004 XL1200 with our CRUSH service to it's original XL1200 heads, a 30 degree reverse dome 1250 kit, a set of our CRUSH 600 cams, a Mikuni HSR45 carb on a Billet Manifold, and a Samson Caliber exhaust system. It's a pump gas street motor with excellent reliability and longevity.


Crush your competition but not your wallet with a set of these heads!


Tech Tip: Don't order your heads with more or less spring than you need, instead match it carefully to your application. More spring pressure than necessary causes extra wear and less than necessary causes valve float or worse.


Crush Head Service
Crush Head Porting Service - Pair
With 7mm Stainless Valves, Striker PAC Alloy Beehive Springs, and Ti Retainers (for cams up to .600 lift)
Cams and Pistons You'll Use, Target CR:
Crush Head Porting Service - Pair
With Sledge Hammer 5/16" Stainless Valves, High Lift Springs, Ti Retainers (for cams up to .700 lift)
Cams and Pistons You'll Use, Target CR:

Crush Head Service Options
Front Mount Bracket
(to Adapt XB/04-Up XL1200 heads to 86-03 Models)
$14
Intake Manifold Flanges (Pair)
for 2007-Up Sportster Heads
$12.30
Machine Squish Band for Angle Dome Pistons (Pair) $80

Specify Angle:

Machine for Second Spark Plug (Pair) $100
Machine for External Head Drains (Pair) $140
Machine, Drill, Tap Breather Bolt Holes on XB Heads (Pair) $60

Crush Head Service Valve Sizes
Head TypeStock Intake
Valve Size
Crush Intake
Valve Size
Stock Exhaust
Valve Size
Crush Exhaust
Valve Size
04-up XL12001.810"1.900"1.575"1.615"
Thunderstorm1.810"1.900"1.575"1.615"
XB1.810"1.900"1.575"1.615"


Sledge - $1100:

Hit it as Hard as You Can, Use a Sledge!

For your maximum-effort engine, we offer the Sledge Hammer service.


Harley Davidson XL1200R Sportster Cylinder Heads CNC Ported with Big Valve Treatment

The Sledge service builds on the Smash service, including all of the high-tech preparation and premium componentry. But what if your application needs even bigger valves, that require a seat change? What if you want to use an angle dome piston? Or install compression releases? Or dual plug your heads?


Sure, you can add those services (and others) to your Smash heads ala carte. But the Sledge service includes any or all of these extras for no extra charge, saving you money!


But the real advantage to the Sledge level is a whole different, exclusive porting process. You see, CNC is a great way to port heads. It results in far more repeatability and consistency than is possible with a human using a die grinder. But it's big strength is also it's big weakness; every port comes out the same.


So what do you do when the size of your motor, and the way you have it cammed, and the way you intend to run it, is not a perfect match for the CNC port profile? Well, until now your choices were to get a hand porting job (and hope that the person with the die grinder does it well matched to your application, which is a big "if"), or live with a one-size-fits-all CNC porting job.


At Hammer Performance, these choices weren't good enough. We set out to solve the problem, and spent years and countless man-hours developing and refining the ultimate solution:


CNC Porting Program for Harley Davidson Cylinder Heads
Screen Shot of the Hammer Performance Port Generating program, set for SLEDGE mode


As you can see, our port generating program, when set for Sledge heads, allows key engine parameters as well as target rpm to be input. Based on these numbers, the program calculates the ideal port cross sectional area for the application and generates a CNC program, on the fly, to perfectly match.


This program was developed in-house, and nobody else has anything like it. If you want the advantages of CNC, but still want your heads custom-fit to your application like a fine Italian suit, Hammer Performance has the answer!


This process has been in place and continually refined since 2003, and it's been used on literally thousands of heads since then. The results have been stunning, from the hundreds of satisfied street riders to the numerous records broken at the Bonneville Salt Flats. Here's an example of what the SLEDGE service can do:


HAMMER PERFORMANCE 115 horsepower Buell 1250 dyno sheet


This dyno sheet is from a 1997 Buell S1 with our SLEDGE service to it's original Lightning heads, a 30 degree 1250 kit, a set of our CRUSH 600 cams, and a Mikuni HSR45 carb. It uses it's factory original 2" collector header with a V&H Slip-on muffler, and it's a pump gas street motor with excellent reliability and longevity.


The Sledge includes even bigger oversized high flow stainless steel valves than the Smash level (up to 2.000" is possible for certain XL heads) and a spring pack matched specifically to your application (up to .800" lift!). Titanium retainers and super strong 10 degree locks are standard at the Sledge level.


Since we need to know all the details on your build to configure Sledge heads, we don't offer online ordering for this level. Call the experts at Hammer Performance today to discuss your project and make sure you get exactly what you need.


CNC Ported Buell XB Cylinder Heads
A set of SLEDGE prepared Buell XB heads set up for an 88ci motor



CNC Machining a Squish Band into a Harley Davidson Sportster Cylinder Head
Any Extras such as Chamber Work are Included on SLEDGE Heads at No Extra Charge

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