Series diesel built up from bits
No sooner had I sent one 1963-built engine out of my workshop (as described in my February column) another one turned up. This one is a diesel with a block casting date of August 16, 1963, still fitted with the old-fashioned bar clamp injectors, and nestling in the engine bay of a really lovely 1967 88-inch hard top.
The vehicle originally left the factory with a petrol engine under the bonnet and was most likely converted to diesel some time back in the 1980s, when secondhand 2.25 diesels were readily available and petrol Series IIAS unloved and unwanted. In 1987 I was offered a Series IIA 88in petrol with a genuine 28,000 miles on the clock for £650. I bought a Lightweight instead, for £100 more. Happy days.
This particular diesel engine started easily, ran well and pulled healthily enough by two and a quarter diesel standards, but was using oil at the rate of a litre every 200 miles, so something was amiss somewhere.
I suspected badly-worn valve guides: the brief was to lift the head, see what I found, and if possible get the oil consumption back down to a sensible level without having to go to the expense of a full rebuild. Given how well it was running this seemed at least within the bounds of possibility, so I set to with spanners and sockets, and managed to get the head off without too much swearing.
The first thing I noticed was a massive amount of carbon build-up on the head and the piston crowns, thickest around the edges of the pistons. This suggested to me that quite a lot of oil was finding its way past the rings. The edge of all four pistons had been eaten away just beneath the injector ports, which is something I had not seen before on one of these engines. The owner told me the vehicle was surprisingly economical on fuel, and I started wondering whether that was because it was running on a diesel/engine oil mixture, which might account for what was clearly combustionrelated damage.
The engine had been rebored +040 which is about as large as you can go on one of these blocks. Sixty thou oversize pistons used to be available but I have not seen any for a while. The bores looked good with minimal glazing and no discernible wear ridge, so at this point I thought we might get away with glazebusting the bores and dropping in a new set of pistons, plus a new set of valves and guides for the head, as the old ones were shot. To complete the assessment of the work required I needed to remove the old pistons and conrods, and at this point everything went pear-shaped.
Number four big-end bearing was worn down to the backing metal and had started to score the crankshaft. To be honest the marks were light enough that for a budget job I would have been happy to run some wet and dry paper round the journal and fit a new set of bearing shells. But then I turned the old shell over, looked at the back and saw the marking 010. The crankshaft had already been re-ground, which is a questionable practice on 2.25 diesels with the threebearing crankshaft.
The factory manual (1969 edition) stated that regrinding was permissible but that great care must be taken to radius the journal edges. By the time the Series III was launched the guidance had changed, with the manual stating in capital letters: ‘CAUTION. DO NOT fit an undersize crankshaft to a diesel engine’. Incidentally, this warning only applies to the three-bearing crankshaft: the later five-bearing crank can be reground with no worries.
New three-bearing crankshafts are available at a surprisingly reasonable price, and if this had been the vehicle’s original engine I would probably have advised the owner to go down that route. Instead I had a hunt around the dark recesses of the workshop and found the following items: • A 2.5 diesel block; earlier type with the recess in the front to take a timing chain tensioner. Bored +020 with good unworn bores. Will need the oil feed for the chain tensioner drilling out, this being the only real difference between the 2.25 and 2.5 blocks. • A 2.25 five-bearing crankshaft, standard
size with unmarked journals. • An early five-bearing diesel flywheel and housing, with the timing pointer and flywheel marks required to time the injection pump. • A brand-new set of 2.25 diesel pistons, size +020. I love it when a plan comes together. The old head will be going off to my friends at Cambridge Rebores for new valve guides and hotspots, the old engine will also donate its timing cover, injection system and conrods, and the vehicle’s owner will end up with possibly the only five-bearing diesel with bar clamp injectors in the country. That should confuse the rivet-counters.