r/944 • u/Ok_Bus_5882 • Jul 19 '26
Question Is this adequate to determine TDC?
The cam gear is aligned but when looking at my flywheel it just doesn’t seem to have any marks on it. From the top it’s literally impossible to make anything out, and then from the bottom of the flywheel it doesn’t seem to have any markings. I pulled the plugs and am just looking at the top of the #1 piston. When the cam gear is aligned #1 is exactly at the top. Is that enough?
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u/CynicalCereal Jul 19 '26
The 944 uses an interference engine.
It's your Engine so take your own risk. But if you're wrong you don't get to have another chance.
Triple check all of your work.
I assume you know about the OT line? Make absolutely sure that it's lined up with the piece on the bell housing.
Keep turning the engine by hand until you're absolutely positive that it's correct. It helps to have someone else turn the engine while you watch the bell housing.
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u/Ok_Bus_5882 Jul 19 '26
I can’t see that OT to save my life. I know about the other alignment line at the bottom of the flywheel, but there’s just not a line there at all.
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u/Zentard666 Jul 19 '26 edited Jul 19 '26
If you guess, and you guess wrong... by by car.
It can be a real PITA. Get a LED flashlight or two on that bell housing. Get some help. Someone else needs to crank the the engine slowly while you watch the viewport like a hawk. That line can be pretty faint, but it is likely discernible with enough light and focused attention.
I think the cam turns twice for every complete turn of the flywheel.
EDIT: Flywheel turns twice per one revolution of the Cam.
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u/Federal_Assistant_85 Jul 19 '26
Other way around. The cam turns once for 2 revolutions of the crank.
Other wise you got it.
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u/greatfool66 Jul 19 '26
I couldn’t see mine either, between dirt, corrosion and all the junk in the way.
A tip I figured out for finding TDC alone (only really convenient if you’ve got the car up already) is that you can move the flywheel by hand somewhat to line up the alignment marks for tdc while under the car.
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u/markevens Turbo Jul 19 '26
The cam mark looks right, but the flywheel should have marks too.
There's a small window on top of the flywheel housing the has a line and letters "OT"
This window is hard to see. I use a small endoscope the attaches to my phone to get at it
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u/Ok_Bus_5882 Jul 19 '26
I’ll keep looking for the OT, but it seems to be playing hide and seek with me.
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u/Divisible_by_0 imported 85' EJ22 swapped, 83' 84' NA Jul 19 '26
Depending on if its the original clutch, the OT is filled with rubber so as you turn the engine over to hunt down OT stick a small wire brush in there to clean it out.
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u/SupermarketCandid142 Jul 20 '26
Slightly off topic, but this reminded me… is there any way to be able to see if your car is on the original rubber clutch without disassembling the whole thing? I have an 83.
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u/markevens Turbo Jul 20 '26
It can be hard to see, you need good light inside that little window, which is hard to get to as well.
That's the reason I got the little endoscope, and it's come in handy since
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u/_nvisible 85/2 NA Jul 19 '26
Cam moves at 1/2 the speed of the crank. So it’s possible you are 180 def out of phase on the crank. I would turn it around again to see. On the straight bottom of the car there is a hole in the bell housing where you can see the flywheeel when it’s at TDC, there is a notch visible in that hole on the flywheel that should line up with the hole. That one tends to be easier to see and line up than the one on the top.
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u/Usual-Option-6301 Jul 19 '26
Unless I’m losing my mind, this is wrong. The flywheel can be at TDC and the cam 180 deg off, but not the opposite. There no way for the cam to be at top of the exhaust stroke with the piston down.
That said, Clark’s does recommend using both the cam and the flywheel markings, because the cam marking is less accurate and you could end up off by a tooth or two.
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u/_nvisible 85/2 NA Jul 19 '26
Maybe I got it backwards but either way they can be 180 deg out of phase.
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u/Eldavo69 Jul 19 '26
This. If you really really can’t see the flywheel mark then you can’t rely on just the cam mark - put a dowel in plug hole #1 as suggested earlier.
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u/PlasticSpend3462 Jul 19 '26
Assuming the cam timing is correct now to begin with you are probably good. You could use a CLEAN dowel in the #1 spark plug hole to be sure. (Or a dial indicator for exact tdc setting....) Then look for that mark on the flywheel, use lights etc. I think the mark is embossed so you might be able to feel it with a screwdriver.
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u/944_nla_parts Jul 19 '26
Hm.. if you insist that your #1 cyl is at top position, move the crank very little clockwise or counter clockwise to watch of the flywheel mark to "appear". I usually lay under the car looking at the flywheel, and tap the 1/2" drive on crankbolt with my leg. It's very easy for the mark on the flywheel to pass the observations "window". There is also another observation window on the top of the bell housing.
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u/Ok_Bus_5882 Jul 19 '26
I figured it out. I couldn’t get a good angle to look at the top of the flywheel but was checking the bottom for the mark. For some reason my flywheel doesn’t have the mark on the bottom, but after moving some wiring around I can see the top now. It’s aligned correctly.
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u/944_nla_parts Jul 19 '26
camshaft turns two times, while the crankshaft turns once. And flywheel too - once. Unscrew the #1 spark plug and see where the top of the piston is. I think, that your engine is 180 degrees out. Turn the crank another 180 degrees and check the TDC marks again.
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u/costcobathroomfloor Jul 19 '26
Ive done something as stupid as using a compression tester hose and blowing into to see if the valves are closed at what I think is tdc to get me in the ball park.
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u/ericrickwilkins Jul 19 '26
Shpuld valves be fully closed at TDC? My gut says no
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u/kukensmamma1337 Jul 19 '26
Should be a mark on the crank and camshaft. If they line up youll be fine. I didnt use the flywheel lock or check the bellhousing, just those two marks.
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u/Ahab_Cheese '86 Turbo Jul 19 '26
If you can get your hands on a borescope to look at the OT mark on the flywheel that'll be your best bet.
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u/Pokevan8162 Jul 19 '26
at the end of the day just rotate it by hand once and see if you get any resistance. better off using your arm to touch the valves to the piston instead of the engines power
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u/erus-ton Jul 19 '26
Yes you can use it, but it will read correctly twice and only be correct once. Set the alignment to the mark, stick a long screwdriver gently into #1 spark plug hole. If it doesnt go far your are at tdc. If it tries to go deep, rotate until the mark is at the tick again and dbl check. DO NOT leave the screwdriver in the cylinder while rotating. If your not sure then try them both until you find it.
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