How to successfully replace an Imp head gasket

Change that gasket / by Mark Daniels. - Impressions Aug. 1986

1. Remove engine from car, leaving transaxle in vehicle
   • consult workshop manual if unsure
   • Manuals state that the engine-transaxle assembly must be removed as a single unit on the Van and Husky models, but this is not necessary, according to the author
2. If not already done, remove inlet and exhaust manifolds from cylinder head (on Sport models: disconnect manifold heater hoses from head)
3. Use a 3/8" square drive 7/16" .F. socket to remove the 8 nuts that secure the the cambox to the head. The fuel pump need not be removed from the cambox
4. Band back the tabs on the camshaft sprocket and undo the camshaft bolt with a 9/16" A.F. ring spanner. Pull the sprocket off the camshaft and remove it from the timing chain. Keep an eye on the dowel, as they can become loose and fall into the sump. Hang a weight on the chain, to prevent it falling into the engine.
5. Remove the camshaft by progressively loosening and finally removing the eight 7/16" A.F. nuts that secure the tappet housing to the cylinder head. With the engine laid on its side, the tappet housing and camshaft can be drawn off the studs taking care not to dislodge the shims which will either remain in the tappets or the tops of the valve springs. Invert the tappet housing and place any shims still on the tops of the valve stems in their respective tappets. The tappet housing should be stored in this inverted position, until it is required for re-assembly.
6. Slacken and remove the ten 9/16" A.F. bolts and the two 1/2" A.F. nuts in the order shown in the workshop manual. Remove washers.
7. Lift off cylinder head. If it is stuck, strike it lightly with a hide-faced hammer, to unstick it.
8. Remove head gasket
9. Remove spark plugs and water temperature transmitter from cylinder head and anything else that may protrude below the gasket face of the cylinder.
10. Turn the engine over until the pistons are half-way down the bores to ensure that the timing chain does not become tangled, and stuff rags into bores.
11. Use a piece of 80 grit emery tightly wrapped around a piece of plate glass or polished steel (approx. 4" wide by 12" long by 1/4" thick) to skim the top of the block, while using moderate pressure and backwards & forwards motion along the length of the block. This will remove all traces of gasket, sealant and any surface irregularities.
12. Take the cylinder head to a good engine reconditioner or to an engineering works, (see yellow pages), and have the head skimmed until it is perfectly flat
    • This can be tested using a dial test indicator (D.T.I.) on a machine table. Feeler gauges and a stell edge will not give a true indication
13. Re-assemble, using a Reinz head gasket
    • Under no circumstances use the copper-asbestos-steel gasket offered by some accessory shops
    • Do not forget to renew the small rubber O ring in the head gasket
    • Oil all bolt threads before re-assembly
14. Pull the timing chain through the head and secure chain tensioner to head so that the top of the tensioner is flush with the top of the head, and the timing chain will not be under tension.
15. Replace head bolts and nuts and torque down using a reliable and accurate torque wrench
    • Hire or rent one if necessary
    • Do not attempt to make do with a cheap dial reading type.
    • All bolts must be tightened to the specified torquewrench settings, and in the correct order
16. Support the timing chain as you turn the engine from the pulley and in a clockwise direction, until piston no. 1 is at T.D.C. (feel for it with a screwdriver through the spark plug hole), and the rotor arm is pointint to no. 1 plug head
17. Place shims on the tops of their respective valve stems and replace tappet housing complete with tappets and camshaft on its studs. Replace washers and nuts, but do not tighten yet. Replace camshaft sprocket until the line on it is in line with the top surface of the head. Now tighten tappet housing nuts to the correct torque: 6 lbs ft.
18. Put the timing chain around the camshaft sprocket and slip the chain around the sprocket until it lines up with the camshaft drive pin. Take care not to turn either the crankshaft or the camshaft while doing this.
19. Release the timing chain tensioner
20. The rest of the assembly procedure should be quite straight forward
    • New gaskets should be used
    • Replace both the thermostat and the temperature transmitter with new items
    • It is recommended that copper-ease or something similar should be used on the head bolts to help prevent corrosion