mpbarrett Posted June 14, 2018 Report Share Posted June 14, 2018 I am starting to rebuild my rebored engine for my Herald. its got a new camshaft to go in and new drive gears and chain. I have realised that I don't know how to setup the timing/position of the drive chain to the camshaft! I can rotate the crank round until its at TDC but I am unsure what the valve position should be at the point. At the moment the engine in on the bench and it doesn't have a head on it but I can measure the cam shaft lift by using a dial gauge onto the cam followers (by using the push rod and centralizing it in the block). There must be an easy way of doing this. Will have a Google but all suggestions welcome! cheers mike Link to comment Share on other sites More sharing options...
mpbarrett Posted June 14, 2018 Author Report Share Posted June 14, 2018 ok so a quick bit of Goggling brought up a post on a USA Spitfire site by John Davis. "Then, use "Equal lift on overlap". This refers to the four stroke cycle. At the end of the exhaust stroke, the inlet valve starts to open before the exhaust valve is fully closed, so that at a certain point, they are both open and lifted by the same amount. This point should be at TDC! So set the crank to TDC, and then rotate the camshaft until the inlet and exhaust valves are equally lifted. Then install the cam sprocket and chain. Your cam is correctly timed! Do this on No.4 (or 6) cylinder and then you know that No.1 is timed for the ignition stroke. It's easiest to do with two dial gauges and stands. but they aren't very expensive these days. This method works with any camshaft that is 'symmetrical', with cams that move up and down the same way and are evenly positioned on the shaft. Good luck! John" As the new cam is symmetrical I will give this a go. Mike Link to comment Share on other sites More sharing options...
Pete Lewis Posted June 14, 2018 Report Share Posted June 14, 2018 the other way to get the cam lobes tdc is blue tack a card disc on the cam , turn to get max lift on the lobe turn a to get the dti to drop say 0.05 mark disc turn other way to the same drop and make disc the tdc of the lobe is halfway between the two marks john also loves a piston stop , which simply blocks the piston rise near the top , protractor disc on the crank mark clockwise to the stop and anti clock to the stop half the marks and there is crank tdc without trial fitting the timing cover the cam sprocket hole sets give 1/4 tooth increments depending which pair you use Pete Link to comment Share on other sites More sharing options...
Anglefire Posted June 14, 2018 Report Share Posted June 14, 2018 I drew a cam timing disk so I could stick it to the pulley - link to the thread is here Link to comment Share on other sites More sharing options...
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