Getting off lightly
CAR: 1970 Lamborghini Espada
OWNER: Harry Metcalfe
With the Espada’s engine out and on the bench (see last month’s), it’s time to delve inside and finally discover why it had an unsustainable appetite for coolant and why its crankcase was breathing so heavily.
First job is to remove the cylinder heads. These have a habit of being sticky on a #Lamborghini-V12
of this vintage but we’re in luck because, when this engine was last rebuilt in the mid-’80s, all the cylinder studs had been liberally wiped in copper grease. So the heads slip off with little effort. It soon becomes clear that both head-gaskets are knackered, which is the cause of all the coolant issues. But instead of coolant leaking into the cylinder, combustion gases were leaking into the coolant passages under compression. That’s why the system was getting overpressurised and coolant was bubbling past the radiator cap. Weirdly, this is good news as it’s an easy fix, but it doesn’t fully explain the low compression readings. So the next job is to remove a couple of pistons. Cylinders nine and ten had the worst leak-down results, so these pistons are removed first. I’m hugely relieved to discover that the big-end shells show little wear, but the less-good news is that as each piston comes clear of the block, the piston’s top compression ring drops to the floor because they are broken in half. The middle oilscraper rings are very worn, too.
It’s the same story on ten of the twelve pistons: no wonder the engine breather was puffing so heavily at tickover.
Again, this is actually good news because we have the answers to all of the engine’s ailments and none of the causes are very serious. It looks as though new piston rings were fitted to the old pistons the last time this engine was rebuilt, but either they weren’t matched exactly or the ring grooves in the pistons have worn. Iain Tyrrell measures the top compression rings at 1.55mm thick while the groove in the pistons is 1.66mm, so each ring has been oscillating up and down at high frequency in the piston and eventually breaking up.
There are no more surprises inside. A bit of wear in the valve guides needs attention, and all the valves had been fitted with rubber valve-guide seals from a Ford Pinto during the last rebuild. These look as if they have been capturing oil and then leaking it down the guide, making oil consumption worse, rather than better as the previous engine builder must have hoped.
So I’m finding that, far from being the nightmare it could have been, this whole engine-rebuild process is enthralling. The next job is to extract the cylinder liners from the block and send them off for a slight overbore to 88.5mm (88mm is standard). New forged pistons are on order and the beautiful steel crankshaft, milled from a single billet, will be polished and balanced.
I’ll report back once the rebuild begins but, for now, I’m just happy that the Espada engine is in such good hands. I look forward to its return, probably even better than it was when new way back in 1970.
From top A big space where the engine used to be; stripdown begins with removal of front-end drives; coolant loss was down to leaking head gaskets but head castings are fine; top piston rings had broken.