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Turning Cam Without Turning The Crank


esty

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steve figured out that the timing's off on the engine and is the reason it won't start...he removed the chain cover, has the chain tight on the crank and need to turn the cam to align but is having little success doing so...he can turn it to close to the right position then he can't turn it anymore

 

he tried putting 2 of the sprocket bolts in and using a screwdriver, prying the cam around but got to a hard spot and the bolt snap'd...luckily wit enough to get out with needle nose vise grips

 

he took out the dizzy and the fuel pump to relieve all the pressure possible but no joy...how do you turn the cam to get proper alignment 

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The bolt snapping indicates something is seriously wrong--i.e., a valve is hitting a piston and that is why it won't turn. Without any more details, such as why he thinks the timing is off and by how much, as well as the configuration of the engine (cam and compression), hard to say more. I found with a big cam and high pop-ups that I could not advance or retard the cam more than a degree without getting to close to comfort on interference. You need to think this through--don't force it or it will only get worse.

 

--Fred '69 & '74tii

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Not sure what timing is off?  Is it distributor timing or cam/crank timing?  But to answer your specific question you need to remove the timing chain in order to move the cam by itself.  Make sure you verify that the crank is positioned a top dead center with cylinder #1.  There is a vast amount of info for setting the crank/cam/distributor timing in the archives.

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it's crank/cam timing...he has the crank positioned as it should be (piston at top of stroke) like in this picture

 

Picture1.png

 

but when aligning the crank the cam is off of it's mark....he thought by removing the chain and sprocket that he could position the cam then realign the sprocket to the chain and have it set but is stuck on turning cam....he did back off on all the valve adjusters as suggested but still can't turn it any more

 

osbh3s.jpg
the cam is not aligned with its mark as pictured...
 

 

assume oil tube is at 12 o'clock, the mark on the cam is at approx 2 o'clock

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If the chain is out of the way, I usually use a rubber strap wrench around the cam sprocket....

 

 

after reading the above....we're concerned that a valve might be hitting a piston...he thought about your idea of putting the sprocket back on the can to turn it but after reading the dreadful info above stop'd until someone offers more advise

 

is it going to be necessary to pull the head again just to set the cam position....we could set the cam by putting the pulley and chain back on and turning the engine by hand to get the cam positioned but then the crank is off it's mark

 

how then would we turn the crank to alignment with the chain off the cam without dropping the chain off the bottom sprocket.....

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Esty, wait ill be right over....................wish I could but it sounds like your cam sprocket is off by one link remove sprocket and walk the chain in direction you need to move it, hands on you will see which way to go, remember cam and crank spin in same direction so move crank a click in same direction as cam timing mark is off. Dont try to start this engine until it spins freely by hand or with socket on crank nut, if still binding take a smoke break and try to think like a German, it works every time for me. Keep us posted.................

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i doubt seriously there is a valve interference problem...we spun the engine a lot in the last 2 days, after torquing the head without issue...it just wouldn't fire

 

he got the cam aligned (turned it with BF channel locks)...the machined mark is under the oiler rube and the indexing hole for the pulley is at 6 o'clock....he only has to finesse the sprocket around to align it with the indexing pin and bolt holes.....easier said than done though...it took him a long time and a lot of cussing to get it on the 1st time

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he still has to fight putting the timing chain & sprocket back on...is there an easy way ?

 

then the valves need to be adjusted which will also be a 1st for us...our son or steve's brother always did that for us but both moved away so we're left to fend for ouselves

 

after it's started he absolutely will do a compression test

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Esty  there is an easier way to install chain but and its a big butt, if you remove the nut on the cam chain tensioner, that round du dad that sticks out of the front cover, it will make it easier. now the butt, gettin said spring and nut back in can be as hard as installing the cam sprocket. Is this a new motor? f so sqwirt a little oil into the spark plug holes, might of caused the hard spinning and wont hurt a thing

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Esty  there is an easier way to install chain but and its a big butt, if you remove the nut on the cam chain tensioner, that round du dad that sticks out of the front cover, it will make it easier. now the butt, gettin said spring and nut back in can be as hard as installing the cam sprocket. Is this a new motor? f so sqwirt a little oil into the spark plug holes, might of caused the hard spinning and wont hurt a thing

as far as i know, it's not a new engine....he'll get up in the morning and start all over wrestling the chain and sprocket....i sure that he wouldn't want to take anything else apart that doesn't have to be...

 

thanks to all of you guys

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If you really know exactly where on the cam gear you want the chain then you can ignore rotating the cam and just rotate the bottom end with a 30mm socket and long ratchet. Just keep track of things so you know that you are turning the right direction for what you want to do. Did you already remove the chain tensioner? It is not that hard to put it back in and bleed it with a long screwdriver. Just because the engine turned over before with no interference does not mean that there will be no interference it you advance/retard the cam 10° by shifting one tooth. Again, depends on engine but you have not yet posted specs. Are you SURE it is not something else? I have always been able to move a cam, even with dual springs, with the 2-bolt and screwdriver method. That broken bolt raised a red flag for me.

 

Best of luck,

Fred

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