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Timing mark alignment????


conorkaby

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1998 1.6K Supersport: I'm in the process of replacing the timing belt but have a potential problem. As per the Haynes I set the cam timing marks to 90 deg BTDC, inserted the Draper cam lock tool and and had the girlfriend stomp on the brakes with the car in gear as I struggled to undo the crankshaft pulley bolt. There was a bit of a graunch and the locking tool appeared to have slipped and dislodged.With a longer handle I was able to release the crank pulley bolt and so I reset the cam timing marks again and loosened the tensioner. At this point I decided to check the timing marks were aligned and noted: the cams were aligned as per the book and the locking tool was in place but the two indents on the crank pulley which are supposed to sit either side of the casing mark are approximately one tooth in advance. Is it possible that the belt may have jumped a tooth whilst I struggled with the crank pulley bolt with the camshaft locking tool in place? When I fit the new belt should I set everything as per the book ie. the dots on the crank either side of the casing mark or should I reset as I found it and assume that the belt cannot possible slip a tooth with the tension set and that this deviation is deliberate?
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I suffered the same problem when I undid and re-tightened my crank pulley bolt - indeed the belt can slip a tooth. The trick is to not fit the cam sprocket locking tool until the crank bolt has been tightened, but after you have made sure the cam sprockets are correctly alighned with the crank pulley mark.

 

The problem with locking the crank pulley and the cam sprockets is the backlash in the transmission putting a tension on the belt enough to make the belt slip. Under normal running, this can't happen because the cams are free to rotate.

 

I found it a REAL pain to realign and had to remove the belt and start again.

 

I also decided to use thread-lock on the crank bolt because that's one bolt I didn't want to come undone.

 

Good luck 😬

 

BRG Brooklands SV 😬 It seems that perfection is achieved not when there is nothing more to add, but when there is nothing more to take away. (Antoine de Saint-Exupery)

 

Edited by - Tony C on 8 Feb 2005 21:01:52

 

Edited by - Tony C on 8 Feb 2005 21:15:14

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I'm no expert in this field..............BUT. If I understand you correctly, putting the cam locking tool in whilst you're attempting to undo the crank pulley bolt, is in effect locking the engine using the timing belt against the locked camshafts. The tool you describe is put there to maintain the cams relative to each other whilst the belt is off, not to lock the engine in position. There's always a bit of wind-up in the transmission & I can't help thinking that you're toothed belt may well have slipped as you attempted to slacken the pulley bolt. Without wishing to alarm you it may be wise to consult an authority on the possibility of any metallic contact under the conditions you've described.

 

As for putting threadlock on the pulley bolt....................I'd approach this with caution. I can't remember off the top of my head the torque figure for this, but it's V. tight. Torqued correctly this bolt won't come out. Using threadlock may cause a bit of swearing if you've ever got cause to remove the pulley bolt in the future.

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What methods have people used to lock the crankshaft solidly in position with the engine in-situ. The tool I've seen is for use with the engine out of the car.

 

Jamming a metal item (such as a screwdriver) between the starter ring and case, in my view, is not a terribly good idea.

 

Putting the car in gear and applying the handbrake does work, but the transmission backlash is a problem - by the time the backlash is taken-up there is little room left to actually tighten the crank nut.

 

I seem to remember someone's crank pulley nut loosening in service - sure thred-lock will make it more difficult to undo the nut in future, but that's something I'm willing to endure.

 

BRG Brooklands SV 😬 It seems that perfection is achieved not when there is nothing more to add, but when there is nothing more to take away. (Antoine de Saint-Exupery)

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Thankyou to everyone for the input. I'll take a look at the sprockets later today but in the meantime hope that the relatively soft aluminium of the cam lock tool has not damaged the surface of the sprockets. Hopefully any forces imparted on the cam sprockets will have been insufficient to cause other problems such as leaking. Like Tony, I am reluctant to jam a screwdriver into the flywheel and will first try to torque the pulley bolt with the car in gear and the brakes applied but I am certainly tempted to use threadlock.
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As stated above, correct procedure is to slacken the pulley bolt before you position the engine and lock the cams. Your girlfriend-on-brakes method is fine if the clutch is up to it. Repalce the bolt afterwards at 120lbft with threadlock - this is the correct procedure.

 

One tooth belt slip will not have damaged the valves since you were in the "safe"position when it happened. In any case "normal" valve timing is often out by this much. (11 degrees IIRC). When you put it all back together set it up exactly as described in the manual with all the marks aligned. Be prepared to sweat a bit to get the belt on. While you are there check the bearing in the tensioner runs freely and doesn't rumble. *smile*

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Goodies from DVA arrived this morning, and I started dismantling the distribution system. With crank blocked by a home-made tool, undoing the crank pulley at 90 ° BTDC was a piece-of-cake. Undoing the cam pulley bolts was done using the Draper special blue tool and a wrench blocking individually each gear (normally used for motorbikes clutch). I was able to recover the spigot from the old inlet cam as recommended by Dave using a hacksaw. It is now in the freezer for the night while the new inlet cam is on a hot water pipe from the house hot water generator (boiler). I hope that to morrow it will nicely seat into the cam *confused*

By the way, I wonder how the rather unprecise positioning of the spigot on the cam (about 10 °from vertical with cam lobe pointing upwards) can match well with the distributor giving sparks at the right time ...

The anaerobic stuff looks like a yellow jelly in a small transparent bag. Can I use a small paintbrush to apply it on the camcarrier before refitting ?

 

Pierre

 

 

 

Edited by - Pierre Gillet on 9 Feb 2005 20:06:12

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