No TDC alignment on flywheel
 

Hi,

New to the forum and new 944 owner. 1986 NA

My son will be using this car for auto cross and I wanted to do the timing belt as its of unknown age.

I'm an advanced level mechanic but new to 944s. If I use a probe in cyl 1 (not using a dial indicator at this point) I can licate TDC piston position and it aligns with mark on cam gear.

However I don't have any alignment on the flywheel. Nothing in the window, nothing in the notch on the bottom of the bell housing.

If I use the inspection window the only potential alignment mark I can see is a rollpin in the edge of the flywheel but that pin isn't aligned when the cam mark is aligned.

There is a scribe line I can see when I view from the bottom of the bell housing but that scribe line doesn't line up with the center of the notch when the cam gear is aligned.

I'm inclined to go by the cam mark , given the piston is at the top of stroke, and ignore the flywheel.

Would anyone here agree? And is it possible through prior service that the flywheel was removed and reinstalled in the wrong location ?

Thanks for the help.

Pete

The pin in the flywheel lines up with the crank position sensor. When the pin is under the sensor, I'm fairly certain you should see a mark on the fly wheel through the upper inspection hole at the back of the engine and top of the bell housing.

You could turn the engine until you see the pin, then turn it back to top *knowing* it'd be centered. You can also remove the sensor and center the stud in the sensor hole.

The flywheel scratch is invisible more often than not due to dirt and rust.
Go by the piston position.

Just curious whether the flywheel was replaced with an aftermarket aluminum one? Even then I can't believe the important registration marks wouldn't still be there. Also I'd be surprised if someone installed the flywheel in wrong orientation and still have the engine run.

You're using a flywheel lock to prevent drift of the crankshaft, right? If he's autocrossing, you'll need to have one in your tool box since you'll use it more than once. The belts need to be re-tensioned after about 1500 miles as well. Are you replacing the water pump while you're in there? It should be replaced every other set of belts. Also spin the rollers. If they spin freely, you can hear them and they continue to spin for a couple of seconds, chances are they're worn out and should be replaced as well. Good to hear you and your son are doing this together. I envy you.

Flywheel mark suppoda be there........Ya sure your on the right stroke.... intake open, intake closed..TDC ??? Might not hurt to look at the valve action

If the car ran fine before you started this, line up the cam, lock the crank and go to town.

The flywheel will only fit one way, and if the car ran that means it's mounted correctly. The pin on the flywheel tells the computer all about TDC and obviously the pin's in the right place.

After you've done the belt change, have a good hard look brough the window at the top of the bellhousing. Look for a line and the letters OT. They may be faint, but they'll be there. Spin the engine with a wrench on the crank and make sure nothing binds.

Kudos for the father/son project. In my world, wrenching with my son creates memories that will last us both a lifetime. Cheers!

I find that the notch on the bottom of the bell housing is way easier to deal with than the OT mark.

I have found that after aligning the cam mark I will not usually see the flywheel mark right away - it takes some back and forth movement of the flywheel to see and line up the marks (and they can be hard to see - once you find it paint it white) - the cam turns at half the speed of the crankshaft and the flywheel is way bigger - so an inch one way or the other on the flywheel translates into almost no movement at the cam - usually when I align the flywheel mark the cam is a little off but less than a tooth

This is my experience as well.

Yup - fly wheel only fits one way, there is a locating stud on the end of the crankshaft that prevents you bolting it up in any other orientation.

I now have spec aluminum fly wheels on both my 944's, and as they are not that old, the marks are easy to see.

Center that stud you see in the upper window - then move it the direction that would put it under the fly wheel reference sensor while checking your cylinder is at top. This should be TDC, you may be able to get a wire handled brush through the inspection hole and clean any grime off the fly wheel to see the TDC mark.

I had to clean the top of the gearbox of one my 944's in order to read the transmission codes.

Indeed. . .wish I was so lucky. My kids don't give two craps about wrenching, but if my dad had a race car when I was growing up I would have been in hog heaven.

Go around one more time, it'll be there.

Thanks for all the replies.

We were back at it this morning. Made sure I was building compression on #1 as the mark on the cam was approaching. So I know for sure I'm on TDC. Put the cam on the mark and checked the window again. Couldn't see anything. Scratched the edge of the flywheel with a screwdriver a couple of times and barely saw a line. Thought I would have seen a notch.

Looks like I'm good, sorry for the false alarm.

Glad I took it apart. Balance shaft sprocket was finger tight!

I ordered pulleys and tensioners from Pelican and they don't match what's on the car, on the car the timing belt and balance belt both have two adjusters each. I ordered per Pelican and received one tensioner and one idler/roller each.

Off to do some research.

Thank you again.

+1

http://forums.pelicanparts.com/uploa...1526214749.jpg

Mark on wheel and block.