Dynomite

Tech Info - LT5 Timing Chain Calculations

Timing chain breakage although very rare has been blamed on repeated engine pulses or fatigue (dead injector or bad valves for example). The timing chain calculations in this post debunk all such theories on timing chain failure.


LT5 Cranskshaft sprocket has 20 teeth.
LT5 Idler sprocket on primary side has 42 teeth
LT5 Idler sprocket on secondary side has 21 teeth
Each LT5 camshaft sprocket has 20 teeth
LT5 Primary chain has 54 pins
LT5 Secondary chain on LH has 102 pins
L T5 Secondary chain on RH has 94 pins

So...we know the camshaft sprockets rotate half as fast as the crankshaft sprocket.

Lets calculate......Crankshaft sprocket rotates 360 deg or 20 teeth. Idler sprocket primary rotates 20/42 of 360 deg or 20 teeth. Idler sprocket on secondary side rotates 20/42 of 360 deg or 10 teeth. Camshaft sprocket rotates 180 deg or 10 teeth. Exactly 180 deg like it is suppose to.

Now lets see how much of total length the RH and LH secondary chains rotate. Crankshaft sprocket rotated 20 teeth or 360 degrees. Primary chain has 54 pins so it rotated 20/54ths of its length. Camshaft sprocket rotated 180 deg or 10 teeth so for RH chain with 94 pins that is 10/94ths of its length and for LH chain with 102 pins that is 10/102nds of its length.

Lets put this another way.......each time the crankshaft sprocket rotates 360 degees, the RH chain moves 10/94ths of its length and the LH chain moves 10/102nds of its length. Or if the RH chain were to rotate its full length, the crankshaft sprocket would rotate 9.4 times and if the LH chain were to rotate its full length, the crankshaft sprocket would rotate 10.2 times.

Now...let us look at the analysis in above posts wherein a miss fire could cause chain failure.

The bad cylinder miss fires once every two revolutions of the crankshaft. That little tug on the chain would occur on the RH chain 4.7 times as it rotated its full length. That little tug would occur on the LH chain 5.1 times as it rotated its full length. And the little tug from a bad injector would occur at different locations on each chain every revolution of the crankshaft since these (4.7 and 5.1) are not whole numbers.

Primary drive crankshaft sprocket................................Primary chain


Idler sprocket........................................ ...........Secondary chain (LH top, RH bottm)


One of four camshaft sprockets


Last UPDATE of post 1 Aug, 2012

Dynomite

Timing Chain Calculations


Last UPDATE of post 2 Feb, 2013