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Join Date: Mar 2004
Location: Scotland
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Camshaft sprocket and belt change.

Sorry don't like multiple posting!! But this isn't really relevant to my last thread!?

I put the timing belt on today (didn't have time to do balance shaft one) and had a lot of trouble getting the crankshaft to stay TDC without a lock.

I was quite succesful setting the TDC mark (painted on cranskaft sprocket) to the left (by 1cm or so) then allowing the tensioner to pull the crankshaft round to TDC when it tightens the belt. I managed to get pretty close - 3mm out - to TDC (by checking through inspection hole in upper bellhouse) and I'm sure I will get it to align perfectly with this method. Can anyone see any flaws in this?

Also I had to realign the camshaft sprocket with its mark (it was fractionaly out max 3mm) and turned it with a larger socket. I noticed this needed a fair amount of force to turn is this normal? I have just rebuilt the head and would hate everything to eat itself on start up!!

Finally on that note my friend suggested cranking with the coil disconnected for a few turns before starting is this a good idea to get oil circulating, what about unburnt fuel?

Dave
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1991 944 Turbo
2012 VW Passat
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Old 09-13-2009, 01:33 PM
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The camshaft is always under pressure of at least one valve spring, so it usually has "stiff" spots. I don't know what you are talking about "allowing the tensioner to move the crank...", but set the crank to TDC by the flywheel mark as closely as you can get it...same with the camshaft. Loosen the tensioner nice and far, get the belt threaded around the pulleys, get the belt teeth to settle into the teeth on the crank pulley, and pull the slack out of the belt along the straight stretch between the crank and the cam, seating the belt on the cam. It should be very close to fitting without having to move the crank or cam. If not, move either one just enough in the direction that is closest to seating the belt...it shouldn't be much. There should be no more than about half a tooth difference on the camshaft mark. Snug the tensioner down without letting the belt come off either of the sprockets and jumping a tooth. Because all the slack is now on the tensioner side where it belongs, the tensioner will not shift the timing at all. Rotate the engine a few times to settle the belt and set the crank to TDC by the flywheel mark as closely as you can get it and re-check the cam timing mark. It should still be +/- no more than half of a tooth from the mark. Keep in mind, with these motors, any more than 1 tooth off time on the camshaft and the valves will contact the pistons. If you have the spring tensioner, roll the crank backwards about 1.5 teeth on the cam gear before setting the tension or it will tension too loose. Double check for good tension by trying to rotate the water pump pulley with the engine at TDC. The crank has to have come forward directly to TDC without rotating backwards at all for this to be an accurate measure. Good tension will allow the water pump to be turned by hand slipping against the timing belt, but with some difficulty. Too much and the belt grip will make it too hard or impossible to rotate the pump and too little will allow the pump to slip on the belt without much effort. Rotating the engine backwards even the slightest bit will shift some of the "slack" in the belt to the straight side of the belt and will give a false "too tight" reading. All of the slack must be kept on the water pump side of the belt for this to work.

The tension increases quite a bit as the engine expands when it heats up, so having the belt be loose enough to allow the water pump to slip a little is not a problem, but is a good supplemental indication of proper tension.
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1987 silver 924S 210k mi! - Rebuilt motor survived 60K so far. Bottom end balanced, Custom mild ported head, Port matched intake, LR 944MAX chip, Thush Welded muffler, Bilstein shocks, MSD Blaster 2 coil, ect ect...Needs 8 more valves!
2003 Hyundai Tiburon GT 2.7 V6 24V DOHC- New toy/backup plan...Borla cat back, Injen intake. Needs headers and a real set of cams.

Last edited by HondaDustR; 09-13-2009 at 06:36 PM..
Old 09-13-2009, 06:31 PM
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thanks for all that!

"I don't know what you are talking about "allowing the tensioner to move the crank..." "

basically when i adjust the tensioner to take up the slack - there is a fair bit of slack on the long side (pulley side) - this turns the crankshaft to TDC (as I have set it backed off prior to tensioning) as the belt tightens, the camshaft sprocket stays still during this however.

Can I assume that if I get the TDC perfect at the inspection hole and the camshaft mark alligned perfectly if the tension is good everyting should be ok??
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Last edited by strath44; 09-14-2009 at 03:59 AM..
Old 09-14-2009, 03:56 AM
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Quote:
Originally Posted by strath44 View Post

Can I assume that if I get the TDC perfect at the inspection hole and the camshaft mark alligned perfectly if the tension is good everyting should be ok??
Pretty much yes. You may not see both of the timing marks line up exactly due to manufacturing variations, but with the flywheel mark dead on, the cam mark should be very close if set correctly, not more than .5 tooth off. How ever you get there isn't really that important as long as you can get right what you just said.
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1987 silver 924S 210k mi! - Rebuilt motor survived 60K so far. Bottom end balanced, Custom mild ported head, Port matched intake, LR 944MAX chip, Thush Welded muffler, Bilstein shocks, MSD Blaster 2 coil, ect ect...Needs 8 more valves!
2003 Hyundai Tiburon GT 2.7 V6 24V DOHC- New toy/backup plan...Borla cat back, Injen intake. Needs headers and a real set of cams.
Old 09-14-2009, 10:20 AM
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GOT THERE!!

thanks to a new day and looking at it fresh armed with more advice I had it sorted in 30mins!

I managed it in the end with a lot of contortion - I got the tension as I wanted it, gripped the crankshaft (by hand) then locked the tensioner in place with some mole grips in turn locking / catching them against the crankshaft then torqued down the nut! Don't worry was very careful and isn't as bad as it sounds.

To summarise a belt change can be done without a flywheel lock but would make it very much easier!!!
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Old 09-14-2009, 12:40 PM
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