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Doing the cam timing - Single overhead cam

Posted: July 6th, 2006, 7:45 am
by Guy Croft
The technique for setting up (dialling-in) the camshaft on single overhead-cam head is very simple.

Tools needed are a large diameter protractor, magnetic base DTI (dial gauge) with enough range to cope with the cam lift, sharp tipped pointer. I stick the protractor to the pulley with 'Blu Tack', an invaluable substance with many uses in engine building..

If the full lift spec for the cam is inlet 110 deg, this means that the inlet valves should be fully open at 110 crank degrees after tdc, so all we need to do with a SOHC motor is find true full lift on no1 inlet valve, mark it, set the crank at 110 deg ATDC and bolt the head on. Final check and adjust can be done if we have an adjustable cam pulley - with the belt fitted.

I am asked 'do I need adjustable camwheels?' Yes - always use them. This is a race engine website, if you're building a race engine, they are essential. Everyone who did not use them either got in a bit of a mess themselves or I inherited the problem of trying to do cam timing without them to my usual standard of accuracy. I just don't have the patience to explain any more what may happen if you don't use them!

It is not necessary to shim the head prior to this op, but I usually get shimming out of the way first.

In the case of the Fiat SOHC head - this one is a 1300 big valve item from an X19, with my new GC F1 profile, the cam carrier should really be removed after this op, the head bolted down and then the carrier fitted. This is because the head nuts (or bolts, later models) on the manifold side are rather hard to get to, even with a crowfoot wrench.