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Timing belt observations


spud murphy
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Hi all

After the recent marathon engine shenanagans, injection pump, timing belt, fuel delivery components and a busted rad, thought I'd post this up if it's any use

With the engine locked up at TDC and following the Haynes instructions 'feed the new timing belt over the pulleys and tighten tensioner' I found that the cam was pulled away from the correct position when the tensioner was tightened up.

Colured dots in diagram are for illustration

The red dots in the diagram =TDC and when tensioned it would rest at the blue dot. BTDC

The trick was to place the belt on with the cam advanced 1 tooth at the green dot and when tightened up the belt would pull the cam back to TDC.

Hope it helps, couldn't for the life of me see any other way around it and as the belt was so close a fit around the components there was no lee way for adjustment without loseing the tension from around the crank to cam pulley and being a tooth out on the belt.

Runs like a clock now, cheers John

post-3726-1182869863_thumb.jpg

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I thought you had to loosen the IP sprocket bolts which gives u the adjustment needed.

this will not change the timing on the IP as its been locked off with a pin going through it...

this is how i have done it in the past and i think the Haynes give details of this method .

Edit: IP = injection pump

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Yep thats right.

I loosened and turned fully to the right the IP pulley bolts so that when the tensioner was tightened it would pull back left the small amount required. Unfortunately it also pulled the cam back with it.

I found that because the crank cog has got the lip cast into it, it was difficult to slip this on as would have been the case with the unlipped version.

This meant that the belt was placed around the crank cog first then up to the cam via the idler, around the IP then back to the crank via the tensioner, but because by this time so many teeth were in engagement it was impossible to juggle things around to keep tension between crank and cam as required to leave the slack on the tensioner side.

Cheers John

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Yep thats right.

I loosened and turned fully to the right the IP pulley bolts so that when the tensioner was tightened it would pull back left the small amount required. Unfortunately it also pulled the cam back with it.

I found that because the crank cog has got the lip cast into it, it was difficult to slip this on as would have been the case with the unlipped version.

This meant that the belt was placed around the crank cog first then up to the cam via the idler, around the IP then back to the crank via the tensioner, but because by this time so many teeth were in engagement it was impossible to juggle things around to keep tension between crank and cam as required to leave the slack on the tensioner side.

Cheers John

I also found this to be the case when i recently did my with the lipped crank pulley. So the one tooth out approach worked for me too.

Just my 2 penneth

TPK

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Cheers Jim

Yep the allen bolt was out, but as tension was taken up everything wants to move left. Not a problem with the injection pump pulley as this was slack and moved fully to the right before tension applied(pump locked up with the pin) but this movement also pulled the cam round to the left as well by a tooth or so. Had to resort to moving the cam on a tooth so that everything would line up when tightened. Seems to have worked as it's running nice and smoothly now.

Cheers John

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