This is an interesting project that started off as a simple repair job, but ended up as a major rebuild. To start from the beginning, I was asked if I would come and look at this T350, and make the engine run. When I went over to look at the car, all the timing chains and the top of the engine had been removed. I asked if any marks or notes had been made, to make reassembly and the timing easier............ NO!
Now as many of you know, TVR do not put any marks on the components, with regard to setting the timing, it all has to be done very accurately with timing discs and clock gauges. This of course is made much more accurate if you can install a timing disc on the flywheel. Quite simply, it's a bigger diameter, and so more precise. As the engine was in the car, I thought I would have to do the job from the front.
However, when the vehicle arrived, both the engine and gearbox had been removed, which although I was surprised, it would make the job a lot easier in the long run. There was a great deal of debris in the top of the cylinder head, and I was worried that some dirt or small parts may have dropped down into the sump. So the first thing to do was to remove the sump and clean all the components including the scavenge pump.
The sump was cleaned and reassembled along with the scavenge pump. The crankshaft was inspected, and then the sump assembly refitted to the engine. I then turned the crankshaft and to my surprise, the engine locked up. Unable to see why this had occurred, I put a camera down each bore and in No1 cylinder was a small nut, embedded in the piston. The person that had been working on the engine previously must have known about this. This meant that the head would need to be removed, which as it happened, revealed all sorts of issues that would otherwise not been discovered. The back three cylinders showed damage caused by a leaking head gasket, and the gasket itself was burnt away, and of course, the nut !!
Above, the famous nut! To the right the burned head gasket and the mark in the head from the nut. The piston had similar marks which were dressed out. There also were marks on the end of the crankshaft, where the engine had been forced with pipe grips, hence the damage to the piston, and also two of the valves were bent and needed to be replaced.
So the burnt head damaged was gently ground away, and then the area was laser welded to repair the lost metal. Once the new metal was proud of the mating surface, the head was cleaned up. The end result was a perfectly finished surface as you can see from the pictures. The two valves were replaced and all the seats ground to obtain a gas tight seal.
The next job was to reassemble the head, and reshim the valve clearances. However, the exhaust camshaft didn't rotate smoothly in the head when it was turned. You should be able to turn it with your fingers, but it was tight in one spot. I set it up in the lathe, and ran a clock gauge over the bearing in the middle. The cam was 17" out of true, and I suspect it had been tightened down unevenly causing it to bend. A new cam was ordered and fitted, and the valves shimmed to spec. Below shows the finished head, ready to be refitted on the block.
The block was cleaned up and inspected for any damage. The cylinder head was originally bolted down to the head to hi-tensile bolts. However, there are a number reasons why this isn't the best practice. When a head bolt is fitted, it is torqued to a setting, but there is the additional friction in the course threads in the block. Also, tightening the bolt into an aluminium thread has the potential risk of stripping or damaging the thread. These bolts are tightened to a fair torque, but often when the torque is achieved, the bolt may not be as tight as it should be.. This is almost certainly what has happened with this engine, hence it lead to the leaking gasket. So the cure is to fit specially made hi-tensile studs and nuts in their place. The stud screws into the block, and then when the nut is tightened, there is no turning force in the aluminium, and a fine thread is used on the nuts, allowing a much more accurate torque. A lubricant is also used to reduce the friction, and improve the accuracy further. It also allows for a higher clamping force, which stops the head lifting during operation.
Once the head was fitted and torqued up, the camshafts were fitted, and the front timing chain assemblies installed. One of the major issues with this engine, is lack of oil feed to the camshafts and finger followers. The oil is fed from the pump, up the centre of the engine, along the inlet camshaft, round the front of the head and then down the exhaust cam. The oil has to travel 1.5 metres before it gets to the rear exhaust valve. This clearly isn't the most ideal situation, and a modification is in order. Quite simply, a "T" is taken off the oil feed pipe and fed round to the back of the head. So basically there are now two oil feeds, instead of one. Net result, the head receives much more oil, and the problem is solved. The photo's show the upgrade being installed.
This pictures shows the timing chains fitted, and the rebuilt throttle bodies. The exhaust manifolds were dipped in acid to remove the rust, and the painted with a heat proof coating. The front cover received new bearings and seals, which just left the camshaft timing. Now, there are no timing reference marks on any part of the crankshaft or camshafts, so I set about making a timing tool for the job. A large flywheel timing disc was fitted, which was a modified Griffith one, and I made a camshaft tool that allows the timing to be adjustable. Once set, it is a simple job of just tightening the retaining bolts.
The body shell off to the paintshop after the front had been repaired. The car had suffer an accident and the front right corner had been replaced. The rest of the pictures show the car after a complete respray which ended up being an easier thing to do instead of trying to match and blend the colour. It came out really well, looks like a new car now. So in theory it should have been an assembly job, but unfortunately there were some major problems that I was unaware of. The chassis rails were not sitting square to the shell, and after some measuring, it was found that he chassis was bent.
After assessing the damage that the chassis had suffered, it was decided to have it replaced with one that was straight, and in good condition. The new chassis was then shot blasted and stove enamelled satin black. Unfortunately the body had also been damaged and badly repaired. The chassis and body were sent to a bodyshop, and the body essentially had a new front end bonded on not it. Significant damage had occurred to the bulkhead and lower part of the screen. So while the repairs were being carried out, I pressed on with the engine. Above you can see the camshafts being timed. There are no timing marks on these engines, and a number of specialised timing tools are needed to complete this process accurately. The front cover was then fitted, along with the cam cover and the clutch assembly. The engine and gearbox were then delivered to the bodyshop for fitting to the chassis before the body shell was finally installed. Once this has been completed, the vehicle will be returned to me to finish.