rsabeebe

I'm in the middle of a 'slippery slope' repair that continues to widen it's scope. Part of the initial work was going to be a new water pump, timing belt, balance belt, seals, etc., so TDC had to be established and a flywheel lock engaged. Like many others, I had trouble locating the window to reference things in that manner, so I used the lower balance shaft pulley and the 'tang' on the rear timing cover. In addition, I referenced the slot on the flywheel. With those lined up, my cam gear seems to be off 1 tooth and I'm curious if any adjustments should be made upon reinstall. I'm also going to pull the cam tower, as I have a gasket leak above the exhaust manifold. See pics for reference.

Any suggestions for adjustments or should I put it all back as is? I know it's very close, but I thought someone might have adjusted the cam gear over the years.

Appreciate any thoughts. Thanks.

V2Rocket

the slot in the flywheel as pictured is one tooth either way. if you turn the crank ever so slightly to put the slot to the other side of the notch the cam should line up

rsabeebe

well, since the belts, pulleys, and water pump are all off already and the flywheel lock is on, i'll just put it all back together as is. i thought it was probably okay, but still thought i'd run it by everyone here also. thanks!

Tails

Just completed fitting timing belt and balance shaft belts without fitting crankshaft locking piece via starter motor hole and all lined up correctly.

To set TDC piston #1 all marks should line up. To set on TDC I used a small diameter wooden stock through the spark plug hull and turned the engine clockwise via a socket on the crankshaft nut. The engine should be turned over until the stick reach it highest position and then all the marks should line up on the TB sprocket & the balance shafts sprockets with groove and the pointers and as shown in the WSM. Remember the engine need to be turned over twice to bring the marks all into view. The timing mark on the top of the bell housing and the mark on the flywheel is very difficult to locate and also to see correctly ( not much room and you should look directly vertically down over the aperture and use a strong beam torch. When I finally located mine, I cleaned up the area with a long shaft screw drive tang. It is much easier if you use 2 persons. I did mine by myself and it took a lot of getting under the car and then getting up to check the flywheel marks.

The mark should all line up. When they are lined up you can check the grove on the flywheel is in the aperture at the bottom of the bell housing. It is a good idea to mark this as a reference for TDC.

When you fit the new belts and tension up the belts as per the specification in the WSM the marks should all line up and should not be a tooth out.

Tails 1990 951 Turbo S

Van

I don't think so - remember, the camshaft spins at 1/2 the rotation of the crank.

If my memory serves, there are 45 teeth on the cam gear, making each tooth 8 degrees apart. But, because the crank spins 2x for every revolution of the cam, one tooth on the cam gear is 16 degrees of rotation on the flywheel. That window in the bell housing isn't large enough to show a 16 degree sweep! I's say that little window is one or two degrees max.

william_b_noble

line the flywheel up using the marks visible from the top if you can, set it to OT, put the lock on it, and then take the belt off and turn the cam to align the mark on the cam shaft if you have to. you MAY be a tooth off, it's hard to tell - it's not dangerous as it is though - the instructions above to use a stick riding on the piston top is good, but the derivitave of the cosine of the crank angle near zero is zero so that is not the best possible test. The best thing is to shine a bright light into the hole on the bell housing on the left side of the engine (top) and find the pointer and line things up there.

rsabeebe

thank you, van and william. truly appreciate both your input.

as mentioned, since the belts are off - thought i was in good shape based on the overall marks - i would still be able to align the OT (assuming i can find that damn window and after removing the current flywheel lock) and then adjust the cam gear to line up independently? i would have to think, that would at least get me back to where i need to be, if something has been misaligned in the past.

is that accurate and a suggested method?

Van

Yes, that's right. Also, do a YouTube search. I've made a video about this.

Tom M'Guinn

Take you time and find the TDC window on top, next the the speed and reference sensors. With the cam tower off you can turn the motor all you want to find the TDC mark, without hurting anything. Using balance shaft marks to find TDC is not a good idea. The cam gear in your picture appears to be one tooth off. All the marks should line up at TDC -- if moving a pulley one cog would make a mark line up better (as in the cam picture) then it's not close enough, whether it's balance shaft or the cam gear.

rsabeebe

i have watched your 3 part series on the water pump/timing/balance belt replacement in detail (actually where i got the balance belt/tang reference, but i guess that's an obvious known reference for you - although all my references were very close with that BB positioning, as well). anyway, is there a specific video i should look for or are you referring to that set of vids?

Van

No, just that set of videos - but I thought I pointed out each of the alignment marks you're aiming for.

To summarize: I'd leave your crank alone, and just back the cam gear up 1 tooth so that mark is really lined up, then put the belt on.