Are you sure that your damper wheel has no timing marks? All of the ones that I have seen do have at least TDC and a few other marks. They can be tricky to see as can the pointer that needs to line up with the marks.
Without timing marks it is going to be a total guess as to what timing you are running and this really is not good enough. In my humble the solution would be to create your own marks or use timing tape, even then you are still going to have to find true TDC so that you can stick the tape on the wheel in the correct position.
Once you are able to work out what position the crank is in then setting up the timing is not all that hard. There is a long winded process that I have outlined below, it is long winded to ensure that you get everything setup correctly.
1. Remove spark plugs so that the engine is easy to turn over using a socket on the end of the crank.
2. Remove the rocker cover for the 'odd' cylinder bank. (This is the bank nearest the dizzy)
3. Get someone to slowly turn the engine over clockwise whilst you watch the valves, it also helps if you poke a screw driver down the plug hole of cylinder number 1 so you know what the piston is doing. (Cyl 1 is nearest the dizzy). As the engine is turned over using the socket watch for the inlet valve opening. (You can work out which is the inlet valve and which is the exhaust valve by looking at the inlet manifold and exhaust). As the inlet valve opens the piston should be on its way down the bore. As the engine is turned the piston will start on its way up the bore and the inlet valve will close. Stop the rotation of the crank when the piston is at 10 degrees before TDC. This will have placed the engine in the correct position for the firing point of cylinder number 1. i.e. with will be on the compression stroke and just before TDC.
4. I will assume that you have an electronic dizzy here, a points system has no place on any decent engine. Take the cap off the dizzy and pull off the rotor arm so that you can see the 'spikey' reluctance wheel that sits under the rotor arm. You need to twist the dizzy so that one of the spikes on the wheel has just gone past the centre of the pickup coil. (1mm past the very centre of the metal part of the coil). Note that you can twist the dizzy or even remove it and re-fit it an different position if you wish, it does not care! Also note that the dizzy turns clockwise.
5. Tighten the clamp bolt so that you can only move the dizzy with some effort.
6. Refit the rotor arm and note where it is pointing, refit the cap and note which High Tension post (HT post) on the cap is above the tip of the rotor arm. This post will be for cylinder number 1. Following round in clockwise direction the firing order i.e. 18436572. The tip of the rotor arm may be a little way past the HT post but it should be pretty near it.
7. Refit all the spark plugs and connect the leads up to the plugs and the rocker cover. Note the firing order above. Also note how the cylinders are number. number 1 is nearest the dizzy, just behind it is number 3, then 5 then 7. The other cylinder bank starts with 2 at the front, then 4, then 6 then 8.
The engine should now fire up, you will then need to set the timing with a strobe, the actual figures that you should go for is a subject in its own right, to a degree it depends on what induction system you are using....Eddy carb, SU's EFI etc. The all 'in-figure' for your 4.0 engine should be around 32-34 degrees I would have thought. Once the timing is setup with the strobe the dizzy clamp bolt should be full tightened.
If you are bored have a read of this, ”Setting up a standard Lucas RV8 ignition system for maximum performance”………………….
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