valver timing question

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P2soup
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valver timing question

Post by P2soup » Sun Jan 24, 2016 4:32 pm

So with a break in the weather today I decided to change the cambelt on the 16v recently purchased. The one that had been stood for 14 years

Having previously started the engine on starter fluid I know it runs as is.

When removing the cam belt cover and locking the crank pully, I have the correct 3 pins from spooxs. The cam pulleys are in the wrong position. (way out)

Having done this on a mi16 before without issue I generally know how to do it. Although I'm no mechanic

Could there be a reason for this, modifications etc. Cams look stock as do the pulleys. Unfortunately no history came with the car.
Belt is in good condition but obviously needs changing after standing so long

Any pointers appreciated! Thanks.

Kaapelimies
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Re: valver timing question

Post by Kaapelimies » Sun Jan 24, 2016 8:10 pm

The crank pulley might be the one with outer ring vulcanized with rubber to attach the inner part? It has turned overtime. Look that the locking pin in the crank is in line with the sump joint to the block. Either about 9 or 3 o'clock, cant remember which.. You'll find out when you turn the crank so that the pins will fit the cams .
I also have a one-piece pulley from a N/A BX as a tool to check the timing before putting back the vulcanized one.
BX 4x4 estate, several BX Van's and some more normal estates in Finland.

P2soup
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Re: valver timing question

Post by P2soup » Sun Jan 24, 2016 8:43 pm

Have removed crank pulley and put pin through locking slot. Still same position.

Finding this very confusing, maybe put pistons at tdc and manually place cams to original settings?

Tinkley
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Re: valver timing question

Post by Tinkley » Mon Jan 25, 2016 5:54 am

Are you sure it is not using the 'hunting tooth' principle? The XU petrols do and you may have to turn the crank or cam(s) quite a few times to get all the marks to line up. You should also I assume have marks on the belt, old and new and when these all line up with the detents in te cam/crank pulleys, that is the default position for the timing as nominal by the factory. It is perfectly possible to get one or more of the marks correct ie timing dowel (lower crank pulley) and not the others. However rotating the system some turns, more than you might think btw, it will eventually get to the 'all aligned' point.
AFAIK, there's nothing wrong with removing the belt and manually setting it all up as long as all marks/dowels etc are aligned. Obviously remove plugs to help make turning easier..... :wink:

P2soup
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Re: valver timing question

Post by P2soup » Mon Jan 25, 2016 7:34 am

Was thinking as above last night that the bottom pulley (crank) probably has 3 revolutions for one of the tops..... :oops:

Thanks for the advise, will lock tops first this time !

Tinkley
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Re: valver timing question

Post by Tinkley » Mon Jan 25, 2016 8:23 am

The cam runs at half the speed of the crank...... :wink:

https://en.wikipedia.org/wiki/Camshaft
Quite a good animation lower down on the page doing what the DC6 engine does. The intent on not using a blatant 2:1 belt is to spread the load on the cam (valve springs) to different teeth for long life. My old Morini had a 2:1 belt inside the V of the engine to drive the cam and pushrods,life was 12k. My Ducati 250 (single) had bevel gears and shaft (no belt or chain, no head gasket either!) and used the hunting tooth gear principle.

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Kitch
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Re: valver timing question

Post by Kitch » Mon Jan 25, 2016 9:33 am

Weird one, that. It's possible the pulleys have been put back on the wrong way around, but you'd all sorts of fun trying to time it up like that - enough for even the most ignorant of morons to figure out something's not right!

They should all line up straight away. Obviously there is a bit of tension to be taken out of the belt, so they might be 0.5mm out of line or something to begin with, but nothing you couldn't figure out.

Trying turning the engine so the cams line up, and make sure the pins fit in both holes at the same time. The valves are so big on a 16v, that it's possible to one valve to strike another cross-planes if the timing goes tits up. Once you've got the cams aligned, go back down the bottom and see where the crank's sitting. Post a picture up if you can too. I'm wondering if you've got the wrong bottom sprocket fitted.