This week on the blog we're taking a look at the steps you would take to remove or fit your Mini's Cylinder Head...
To remove a Mini Cylinder Head:
The first step in removing a Mini Cylinder Head is to disconnect the earth strap / negative terminal from the battery, along with disconnecting the Bottom Hose at the Water Pump to drain the Cooling System.
Next up you should disconnect the HT leads from the Spark Plugs, (don't forget to label them to get them in the right order when you're putting it back together!). Also disconnecting the Lead from the Water Temperature Gauge Sender Unit at the Thermostat Housing. If your Mini has a breather hose, disconnect this from the Rocker Cover & remove the Air Cleaner Assembly.
Next up, you should disconnect the Distributor Vacuum Pipe, Fuel Hose and Engine Breather Pipe (if your Mini has one fitted) from the Carburettor. You'll also need to disconnect the Kick-Down Linkage Rod from the Carburettor if your Mini is an Automatic.
Then disconnect the Throttle Return Spring from the Carburettor. Removing the two nuts securing the Carburettor to the Inlet Manifold, detach the Carburettor from the Studs & set aside. Where a Cable Abutment Plate is fitted between the Carburettor and the Inlet Manifold, the Plate should be removed with the Carburettor.
Moving on, it's time to remove the two Nuts securing the Heater Water Control Valve and detach the Valve, placing it to one side with the Hose and Cable still attached. You also need to remove the Nuts securing the Radiator Upper Support Bracket to the Thermostat Housing, along with the Bolts securing it to the Radiator Cowl, and then remove the bracket.
Once the bracket is removed, it's time to slacken the Clip securing the small Bypass Hose to the Cylinder Head connection, this is located on the underside of the Cylinder Head, above the Water Pump. Take off the two Nuts, together with their Cup Washers and Seals, retaining the Rocker Cover, and lift off the Cover / Gasket.
The Cylinder Head and Rocker Shaft Pedestal Nuts then need to be removed, by releasing them evenly until the Valve Spring Load on the Rocker Shaft Assembly is released. On models where the Ignition Coil Mounting Bracket is attached to one of the Cylinder Head Studs, remove the Coil and place to one side.
It's now time to lift off the Rocker Shaft Assembly, then withdraw the Pushrods, keeping them in their installed order. Disconnect the Radiator Top Hose from the Thermostat Housing & then remove the manifolds from the back of the Cylinder Head.
Loosen and remove all the Cylinder Head Securing Nuts and Washers (Cooper S engines have a extra Stud and adjacent to either end of the Rocker Cover). Proceed to lift off the Mini Cylinder Head... If you struggle removing the head, tap each side of the head with a Hide-Faced Mallet to free it.
Finally, remove the Cylinder Head Gasket and discard it!
To fit a Mini's Cylinder Head:
To fit a Mini Cylinder Head, the process is pretty much the reverse of removing it - however, you must also:
Ensure that all surfaces of the Mini Cylinder Head & Block are clean, with no traces of the old gasket remaining.
If you removed the Mini Cylinder Head to replace a blown/leaking Head Gasket, then you must check that the mating faces on the Cylinder Head & Block are not distorted in any way.
Fit the Cylinder Head using new gaskets - we offer handy sets for ease.
Don't grease or use a compound on the Cylinder Head Gasket when you're fitting it & ensure that it is correctly positioned (this is usually indicated on the gasket itself).
When installing the Push Rods in their original positions, don't forget to dip the ends in clean engine oil.
Moving on to fitting the Rocker Shaft Assembly, you must ensure that the Rocker Arm Adjusting Screws locate correctly in the cupped end of their respective Rush Rods.
The Rocker Arm Adjusting Screws will need releasing slightly before installing the Rock Shaft Assembly if you have carried out any work on the Valves. Don't forget to lubricate the Rocker Assembly with some new Engine oil.
Next you can tighten the Cylinder Head & Rocker Shaft Pedestal Nuts by following the sequence shown in any technical data book - but be sure to do this evenly.
Models that are fitted with the Ignition Coil Bracket to one of the Cylinder Head Studs, you must remember to re-fit the Bracket after tightening the Head Nuts. It also needs noting that on Cooper S models, you must tighten the additional Securing Bolts at each end of the Rocker Cover last - the data for this can be found in the Haynes manual.
Check your Valve clearances & adjust where necessary. When you have finished the fitting process, you can now re-fill your Cooling System before running the Engine to check for any oil, water or exhaust leaks.