K series cambelt change - in situ?

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StevehS3
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Great thread and contributions. I have never changed a cam belt but for me part of owning a 7 is to learn such things. I was hoping someone local might show me but I think I will have a good read of the Haynes manual and do it alone over winter.

Wrightpayne
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Without verniers to reset its quite straight forward.

I remember reading that mechanics, on certain cars cut the belt down the middle with a stanley knife - engine running :-0 Then cut one half off, slip the new belt on (the half left on keeping everything aligned) then once the new belt half on, cut the remaining old belt off and press the new belt fully home Jobs a goodun!

StevehS3
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Job's a good 'en unless you slice through it completely - then job's a bad 'en!

Standard cams and no verniers on mine.

murph7355
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Is that amount of movement enough to get the belt a tooth out?  It doesn't look to be.

Fanastic contributions so thanks everyone.  Keep it coming :)

First job will be to take the covers off an see what I have. 

I'm not fully understanding why Verniers add to the issues, assuming they're all tight.  More reading/video searching to do.

(And if it all looks like it's getting too much I'll get a pro' to check my handy work!).

Wrightpayne
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The verniers are adjusted to alter the precise point the cams are on maximum lift in relation to the crankshaft (and by default piston position). When you unbolt the bottom pulley the belt sprocket can move (as shown in Andrews video). Therefore the precise relationship between crankshaft and cams is lost. 
 

Hope that makes sense.

 

Ian

revilla
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It's about 6 degrees. No, not enough to get a tooth out, but that's not the point. It's enough to get up to 6 degrees of timing error even with the belt on the right tooth! And 6 degrees is a lot, especially on an engine with large cam lift and big valves.

SV VVC 170 - 170.4 bhp @ 7100 rpm - 142.4 ft.lb. @ 4900 rpm

murph7355
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Thanks both.  Think I get it now.

Presumably if my pulley is shimmed and has no slack, that problem goes away?

(Feels like there's no getting away from the need to get them timed in again really).

Geoff Brown
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As related in #19 my 1.6 K Series had verniers (from Oily Hands) along with Emerald & Jenvys. 

Aligned the marks on the verniers then locked with the locking block. The only disconcerting thing was the misalignment of the lower marks. But I had faith & carried out the belt change twice with the mods installed with no problems. Crank pulley play was not evident.

Wrightpayne
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I wonder if Oilyhands could write a 'how to' shim the bottom belt sprocket? Or is it as simple as cutting a piece of x thou shim and filling the gap? 
 

Once the slop is gone, belt changes with verniers should be straight forward.

 

Ian

 

 

Bricol
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Done correctly, you'd "fit" an over-size key.  

By "fit" I mean an engineering fitter would make it a precise fit "in situ, as required" - as all the best drawings say :)