Re-bored to 0.25mm oversize after releasing seized pistons from barrels. Inlet valves 1 and 2 were replaced due to heavy pitting, otherwise OK.
Known problems:-
Camshaft wear occurs if the engine has been thrashed from cold or regular oil changes neglected. The oil ways to the head are very small and may be blocked.
Cam chain problems - new tensioner blades and cam chain at around 24,000 miles. More
Pistons Are reputed to wear at 20,000 miles. This may be attributed to neglected oil changes or general thrashing to the red line, who knows?. It seems to start at the little ends causing pistons to move about, this in turn cracks the piston rings, then as they disintegrate they destroy the cylinder bores - beware!!
NOTE: Piston bore wear occurs mostly at the top of the stroke, check top & bottom with a piston ring. If the end gap is equal top & bottom but outside the given tolerance of 0.7mm maximum then replace the ring set, the cylinder bores are OK, otherwise have the cylinders rebored to the next size i.e. 51.25mm. Check the little ends very carefully if only replacing piston rings, any doubt then replace the pistons, piston pins & the 8 clips.
Exhaust valve guides wear around 60,000 miles. This is a job for a specialist, have the valve seats reground for the new valves at the same time for a perfect seal.
Leaking head gaskets are usually for the following reasons:-
1 Cap nuts not torqued to the correct 2-2.3 Kgm or 14.5-16.6 lb ft.
2 Stud locking compound not used.
3 Rubber o-rings in the camshaft oil feeds have hardened with age.
4 Some castings were porous from new.
5 Poor quality pattern gasket set, try to use OEM parts if possible.
6 Engine revved beyond its red line.
7 Warped cylinder head due to incorrect tightening sequence, see workshop manual.
8 After at least one hot/cold cycle of the engine the nuts will require one more tighten.
Notes:
On early F models up to s/no.1057306 slightly shorter cylinder studs were used, this allows for very easily stripped threads on the cap nuts, first clean the threads with a tap & die set and have some spare cap nuts to hand before starting. I also like to use a gasket compound like Wellseal by Stag Ltd; on the head gaskets. When torquing down the head always double check the torques are correct by making further passes of the sequence (use a good quality torque wrench).Tip - after replacing head gasket, use old rocker cover gasket keeping the new gasket for use after the first hot/cold cycle and subsequent re-torquing of the head nuts.
Tip - if running the engine hard is to occasionally snap the throttle closed, this will allow some oil to be sucked up the cylinders.