Varying degrees of uncertainty
Q I have just had the head off my Ford Pinto engine. I have discovered that the camshaft sprocket is not the original and there is no pointer for the timing. How do I set the camshaft timing? Paul Dean, via email
A It might be easiest to fit a standard sprocket, assuming it still has a standard camshaft. To time a camshaft from scratch, attach a 360° protractor to the crank pulley. It must be accurately centred. Affix a wire pointer and (taking care to avoid piston-valve contact) calibrate the pointer to read zero at TDC of cylinder one. This can be found by inserting a rod into the spark plug hole so it rises with the piston as you turn the engine. Turn the crank 90° forward to set all the pistons safely halfway down.
Turn the camshaft to a reference point, which you’ll find in the data of the workshop manual or, for an aftermarket camshaft, on the maker’s data sheet. This reference may be the point at which the inlet valve of cylinder one starts to open (typically 10-20° BTDC) – or the point at which it’s fully open (typically 100-120° TDC).
The valve is fullyopen over a period of degrees, so you’ll have to find the mid-point for your measurement. Turn the camshaft to this point, then align the crank to the degree measurement specified in the data. Fit and tension the cambelt. Rotate the engine by hand, making sure there are no tight spots, which might indicate valve-to-piston contact. Mark the cam sprocket at TDC of cylinder one for future reference.