To finish the recent series on cam timing methods, Keith discusses how to set things up the common way.
Keith finds loads of memorabilia with his Mini, Stephen updates us on his dad’s project and Tim buys a buggy!
As a conclusion to the recent series on cam timing, our final method is the one camshaft manufacturers and suppliers advise. It is not the ultimate method, but the easiest in terms of equipment either readily available or cheap enough to purchase. This is cam timing at the push rod.
First, there’s something to be mindful of. Camshaft manufacturers quote specific valve timing figures, lobe centreline angles (LCAs), valve clearances, cam lifts and valve lifts, but rarely – if ever – the recommended cam timing point, or where it should be measured. Some suggest the timing be done at the push rod as described here, but do not say whether the figures they give for each cam spec are actually quoted correctly at the push rod. The lack of any other information suggests it is.
However, setting the cam timing at the push rod is significantly different to what is happening at the valve. The most important point in the valve timing sequence is what is happening and when at the valve in direct relation to the piston position. That’s not the push rod, but the valve.
Probably the hardest part of the push rod method is rotating the crankshaft without disturbing the accurately-set degree disc. Alterations to cam timing that will disturb the degree disc setting can be avoided by fitting the disc to the flywheel end of the crankshaft. Temporarily fitting the flywheel to the crankshaft, then placing a stout rod/lever through one of the slots in the flywheel outer rim to engage on the base of the block, will allow sufficient leverage for you to fit a bolt in the cam gear end that’s tight enough to rotate the crankshaft. You can then use the flywheel fitted with locating key plate and retaining bolt to rotate the crankshaft. The downside is the degree disc will be positioned at the business end of the job. The consequence of this is that the disc will need re-zeroing each time it is removed to make cam timing adjustments, dependent on the adjustment type used.
Cam timing at the push rod is the method manufacturers advise.