Finding top dead centre and timing the camshaft

As can be seen from my earlier posts most of the valve train is very worn.. Not surprising given the miles on the car and it's age. So as I have already mentioned I needed to replace pretty much everything apart from the sprockets (which are in good nick) and the cylinder head.

One thing that you have to consider when fitting a new camshaft is ensuring that it is timed with the crank. For example this means ensuring that when the piston is moving up the cylinder bore on the compression stroke both valves are closed allowing the mixture to be compressed. To ensure that valves and pistons move in perfect harmony the motion of the crank synchronised to the motion of the camshaft via the timing chain. Unfortunately not all camshafts are created equal and it is essential that a new camshaft is timed to the crankshaft when it is fitted.

The first stage of this process is to find top dead centre (TDC) on the crankshaft. This is the position when the piston in cylinder one (nearest the front of the engine) is at the top of it's stroke. This position is generally marked on the crank pulley, but when the engine is in bits it is good to check the marks havn't moved. There are many ways to do this but my favourite uses a device called a piston stop (see above). The piston stop is made up of a piece of steel that is bolted (in this case using the head studs) across the top of the number one cylinder. Protruding from the centre of the piece of steel is bolt. Now when the engine is rotated that the piston stops when it hits the bolt.

To determine TDC a timing disc is first attached firmly to the crank and a pointer e.g. a piece of steel wire is  attached to a bolt on the front of the engine.(see below). The crank is then turned clockwise until it touches the stop. the number on the timing disc that the pointer is next to is written down. The same process is repeated in the anti-clockwise direction. We then know that TDC is halfway between the two numbers.

 In the case below I had already lined up the crank to the TDC mark made when the engine left the factory. The two figures I read off were 26 degrees before and 26 degrees after TDC indicating that in this case the TDC index on the pulley is in the correct place. This is NOT always the case and I have seen figures that are anywhere up to 20 degrees off. In these cases setting cam and ignition timing using the incorrect marks could have caused big issues (bent valves any one!)

Fitting Valve Springs

So next need to fit the valve springs. Now in the past when I have done this I have found it quite fiddly.. The collets that secure the spring to the top of the valve are small and always flick out into oblivion if the spring isn't aligned when you release the pressure...
So this time I made sure I had plenty of collets. In fact I had twice the number required as I had stripped 2 heads, the 9.5:1 and 7:1 compression.

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LATEST NEWS: O yes, should have said, idea of fitting a supercharger is on ice until next winter. Moss have temporarily discontinued the supercharger kit while they carry out a redesign. So will be going back to plan A. Refitting the 9.5:1 and going back to Lucas Petrol Injection.

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 So back to the head.. The procedure for fitting the springs is relatively simple and requires one specialised tool, a valve spring compressor, which you also have to use to take the springs off. Stage 1. Fit the inner valve seat and the rubber o-ring valve stem oil seal. 2 & 3. fit the spring, spring cap and the valve spring compressor and compress the spring. It is worth noting here that there are 2 types of cap on the TR engine. One is in two pieces and the other one piece. The one piece cap fits on the inlet valves while the two piece is for the exhausts.

The two pictures show how the compressor is seated on the head (actually the close up shows the compressor slightly off centre, but I changed this before fitting the collets). 4. insert the two collets into the groove at the top of the valve. If you can't get them in tighten the compressor a bit. I find a bit of grease on the collets helps them to stick. now release the compressor. The release the compressor, and if all is right the collets should drop into place like those shown in 4.