About two months ago I drove a customers Stag where I did made a new wiring harness for. It was a brand new restored Del Lines Stag Estate with around 100 km's on the tripmeter and engine. A bit of running in. From a 80km/h single lane road into a dual lane motorway 130km/h I accelerated from 80 towards 130. Just full throttle overtaking a car with that Stag v8 engine sound in my ears it started misfiring. Just when I thought what could that be a sudden bang and a lot of engine oil smoke/mist escaping from under the bonnet through all the gaps and vents. And missing some cylinders now.
Parking it on the shoulder seeing what happened the oil filler cap was blown off causing the oil mist. About 50 meters back I did find it. I informed the owner and the local machineshop to pick me up. The engine was overhauled at the owners place but it did already see "my" machineshop because my workshop was full of coolant leaking from inbetween the engine deck and head. I have no time to undertake such jobs and the owner agreed the easiest was have it done locally to me so he could drive it back when all was ready.
I knew the machineshop where the engine was initially was overhauled the first time and experienced more faillures of this shop aldough it's "recommended" and well known in the Dutch Triumph world. A friend with a Vitesse had 4 headgaskets fitted overthere and still leaking coolant until they discovered there were recessed and non recessed headgaskets... Another friend had a Dolomite Sprint engine overhauled there and his oilpump was that blueprinted it wouldn't turn. He luckily discovered because he wanted to prime the engine with an electric drill before startup through the distributor hole and the drill couldn't turn the oilpump the rotors clamped inbetween the housing and cover.. The Stag engine in question did already had an issue. Within the first 200 meters something wasn't quite right and there was a squeeking sound. After some investigation that machineshop said the oilpump had jammed. Hearing that story from the owner I said I had a dejavu. Maybe the same thing that Dolomite engine of a friend had a few years before.
After a few day's "my" machineshop called. It had a broken camshaft and if I had seen this before and if yes if I knew the cause. I never have seen a broken camshaft in a Dolomite or Stag. Luckily only some bend valves but nothing major was damaged. I couldn't also think of a reason why the camshaft broke. Maybe one that was dropped in the past? The head was taken off again and repaired and a good second hand camshaft was fitted. All ok again. There was only a slight problem that it wouldn't run properly after the repair. Ignition timing was off and after setting it went off again. I suggested to take the timing cover off to see if the jackshaft locating pin was there. I had seen a few almost shears in my life of these pins. That was the only a reason that I could think off why the ignition timing was moving all the time.
Today the timing cover was taken off and it was a great mess. No teeth on the jackshaft sprocket, the locating dowel broken. Having no teeth on the jackshaft sprocket indicated it got stuck during running. After investigating the jackshaft journals it rapidly became clear these were sanded. The edges of the slots that were factory machined in where too "round" and too soft. No hard edges what normally is. Sticking/grinding marks were also visible. This explained all. First the misfire by an uncontrolled jackshaft. Then the jackshaft that got stuck, sprocket sheared and camshaft timing off. The camshaft timing off meant a valve was being pushed open against a piston top. The camshaft wouldn't turn by that issue and broke in half.
Cause, the "new" jackshaft bore to narrow. I think this was the cause also the first time after 200 meters. Not an oilpump what the owner was told. The jackshaft was sanded to have it better running again in it's new repaired/rebushed bore to save an engine strip and have the bore correct. After the "repair" it was send on the road again and it lasted somewhat longer this time than the 200 meters before.
I feel sorry for the owner but the technical aspect of this faillure was very interesting to find out and a warning for all the people who have their jackshaft bore repaired/rebored. Measure before fitting parts.
Jeroen
