can anyone help, i have just rebuilt my engine consisting of new head,tappets.oil pump.waterpump and all gaskets and seals including rear main so flywheel off. i have not touched the bottem end as it was rebored and re-shelled only 10,000 miles ago. the engine had no vibration before the the build, but when i started it yesterday there is a huge vibration at 4,000 you can feel it right through the car and even through the gearstick. the engine mounts are fine and there is nothing touching the bodywork. I had the same vibration about a year ago and was told it was a distorted flywheel which was 'blue' both sides, i replaced it with a brand new one and it has been fine ever since until now. the flywheel can only go on one way so i can eliminate that, but i did not mark the clutch cover could it be that, or will the whole crank assembly need rebalancing? any advice much appreciated