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Timing belt tension checking methods. - Engine/Ancilliaries - The Lotus Forums Jump to content
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Timing belt tension checking methods.

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Well, I know what it looks like, and yes, it didn't go well. I hung 46kg (100lbs) on an old belt and checked with a Boroughs gauge to try to calibrate it, it read 70lbs. How reliable is this method ?

 

The belt I have just installed on the motor measures 110lbs (same gauge) and feels right, if I slacken off the belt to the 70lbs (as calibrated) then it’s way too loose !!

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The latest official lotus method is to measure the frequency of the belt at 30 degrees before top dead centre (timing dots on cam pulleys should be towards centre but not aligned) using a clavis gauge.

A clavis gauge costs a fortune but you can get "tuning" apps (for tuning guitars etc) for smart phones that measure frequency well.

At 30 BTDC the frequency of the belt when gently plucked or tapped with say a screwdriver should measure 100 to 110 hz on a correctly adjusted belt.

Do a search on here, i think someone loaded up the official addition for the lotus manual on this. Much easier than the burroughs method!


forgot to say....pluck it or tap it between auxiliary shaft and inlet cam

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I've never been sure of the effect of all the extension gubbins hanging out the side of that gauge. I have just the original Burroughs gauge itself, and I use exactly the same sort of calibration rig that you have set up....I assume you weighed the load on bathroom scales?....and mine indicates accurately. You do get variations depending on how you use it...the speed of release of the gauge has an effect on the reading...so you could try letting it release very quickly and also slowly and see what you get. I must see what the frequency method gives, after some research as to exactly what it should be for an 82 Turbo with the trapezoidal belt.

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