How To's  

Cudney Billet Head Installation



Cudney Billet Head Installation

Looking for more throttle response, stronger top-end and a more efficient cooler running engine? Who isn't, how about the Cudney Billet Head from Cudney Racing? I ran this head on my machine last year and though I would share how easy this is to install and some of the benefits I noticed immediately.

The moment you mention engine internals most people get a little nervous. I can tell you with patience and some basic tools you can install the head a couple of hours. I did this in the garage on a quiet day in February.

The Cudney Billet Head consists of basic Instructions and Bill Cudney is available via phone or e-mail to assist when needed. Bill's contact information is included in the package.

The when working on engine components safety is first.

  • Ensure the engine kill switch is "off", remove the tether cord, spark plug leads and spark plugs.
  • This is optional; however, it makes the installation easier. Remove the clutch-cover, drive belt, secondary clutch and air box.
  • Siphon the overflow bottle into a clean container. Remove enough antifreeze to ensure a safe level below the head.
  • Loosen the gear clamps on both the in and out thermostat coolant hoses.
  • If equipped, select the carburetor coolant switch to "off" and remove the coolant line from the head fitting.
  • Disconnect the engine temperature sensor switch electrical wires; there are two separate wire connectors on this sensor for the 800HO.
  • Remove the two upper thermostat hold down bolts. Carefully lift the housing and peel back the housing gasket and save for reinstallation. If possible, position the housing away from the head.
  • Remove all 12 cylinder head bolts. A good rule of thumb is remove one at a time and place it in the new head. This ensures each bolt goes into its appropriate position. In some designs there are various bolt lengths and this method ensures they each are placed in the correct location.


  • Carefully lift off the head, try to do this vertically without any side to side movement.
  • Now that the original head is removed take a look in the cylinder area and note piston tops, rave valves, head seals and cylinder condition. Now is the time to address any issues if necessary.
  • On the original head, remove the two lower thermostat housing bolts and thermostat. Remove the carburetor coolant fitting and temperature sensor.
  • Inspect the thermostat and place it into the Billet head and re-install the two thermostat housing bolts, do not over tighten, 60 inch pounds is adequate.
  • Clean both the temperature sensor and carburetor fitting threads. DO NOT use the temperature sensor gasket originally found on the sensor. Remove it and store it. The new Billet head does not require the sensor base gasket.
  • Apply new Teflon tape to the threads of the temperature sensor and the carburetor fitting and install them on the head, tighten, making sure not to over-tighten either.
  • Your now ready to place the head into position. Before placing the head into position take a quick look into the cylinder area to ensure no foreign objects found their way into the cylinders. Now slowly and vertically lower the head onto engine, try not to slide it in place, this could unseat the cylinder seals. Also, when aligning the lower thermostat coolant hose, lubricant inside hose surface and housing fitting to ensure ease of placement. Place all 12 head bolts into position starting each one a couple of threads using your fingers.


  • Now run each head bolt down into the cylinders. Once each bolt is snug, start the tightening sequence as suggested in the appropriate maintenance manual. The rule of thumb, start from the centre bolt and work outward, alternating in pattern. The torque value is 21 foot-pounds or 252 inch-pounds. Bill will specify the torque requirements in the shipping paper work. Torque each bolt twice to ensure the dome pockets are seated correctly.
  • Install the upper thermostat head gasket and install the two housing bolts.
  • Tighten the two coolant hose gear clamps.
  • Reconnect the two temperature sensor electrical connectors.
  • Reinstall the carburetor coolant line and select the valve to "on".
  • Before filling the coolant bottle ensure all clamps, bolts and connectors are securely in place, then slowly rotate the primary clutch by hand and check that nothing is binding. Fill the coolant bottle to the upper limit. The new Billet head has considerable more coolant capacity. Additional coolant with is required during the run in process.
  • Reinstall the air box, secondary clutch, clutch cover, spark plugs and leads.


  • Clear the area and start the machine watching for leaks. As mentioned in step 21 additional coolant will be needed. Secure the overflow bottle cap and go riding.


The Cudney Billet Head is an easy installation and requires basic tools. A "clicker" type torque wrench is recommended for this application. There is no requirement to replace any engine gasket. Teflon tape is required for the threaded coolant fittings.

My 2004 800HO is equipped with a Cudney Clutch kit and trail porting. The addition of the Billet head was immediately noticed. Throttle response was instant and in wide-open runs the engine was strong and consistent. Other benefits to the installation were its ability to run slightly cooler, I.E. more power! This thing rocks and when compared to other stock machines it runs up top with the big Cats and Doos of the world. This machine can be viewed on Snowtrax Television in April 2005.

Report submitted by Snowtrax Backshift  ©