To fin­ish the re­cent se­ries on cam tim­ing meth­ods, Keith dis­cusses how to set things up the com­mon way.

Mini Magazine - - Contents -

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.

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