doing timing belt.. need to verify TDC
05-09-2009, 03:23 PM
#1
Racer
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doing timing belt.. need to verify TDC
So I followed the procedure at clark's garage for setting TDC - found the "OT" letters from the top side, lined up the groove in the middle down near the starter and then installed the flywheel lock. I now have all the belts off but I noticed there was a mark on the camshaft gear which is about 180 degrees off of the mark on the distributor housing. Am I still ok here or did I royally eff it up?
05-09-2009, 03:37 PM
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No, it sounds to me like you needed to turn the engine some more to get all the markings to align before fitting the flywheel lock. You must put the belts back on to do this, though.
I found it easier to just pull the distributor cap, like you have, and align both the cam gear markings and the balance belt sprocket markings first. When I did this, sure enough, the flywheel was at the OT marking.
I found it easier to just pull the distributor cap, like you have, and align both the cam gear markings and the balance belt sprocket markings first. When I did this, sure enough, the flywheel was at the OT marking.
05-09-2009, 04:19 PM
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The cam turns at half the speed of the crank, so you are on TDC at this point. What I would do is reinstall the belt and slowly rotate another 360 degrees on the crank. Then install the flywheel lock. This will get your cam aligned with the mark. If you are off a tooth or two, you will be fine in the rotation, then once you are back at TDC, pull the belt, you can turn the cam until it lines up.
05-09-2009, 04:42 PM
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easier to align TDC under the car at the bottom of the bellhousing- there is a notch at 6'oclock and a line on the crank that aligns with this when the OT is aligned at the top. Cam sounds 180 out though. Like porscheDoc said, rotate one more time around.
05-09-2009, 05:08 PM
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Thanks for the quick responses..
PorscheDoc - are you saying that TDC is when both the camshaft and bellhousing marks are aligned? If this is the case then that clark's garage article I printed out totally screwed me. It doesn't mention anything about having to align the camshaft sprocket.
So basically I need to:
1. install timing belt
2. remove flywheel lock
3. rotate crank 360 degrees
4. remove timing belt
5. reinstall timing belt and adjust camshaft if it moved
Does that sound about right?
PorscheDoc - are you saying that TDC is when both the camshaft and bellhousing marks are aligned? If this is the case then that clark's garage article I printed out totally screwed me. It doesn't mention anything about having to align the camshaft sprocket.
So basically I need to:
1. install timing belt
2. remove flywheel lock
3. rotate crank 360 degrees
4. remove timing belt
5. reinstall timing belt and adjust camshaft if it moved
Does that sound about right?
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05-10-2009, 01:53 AM
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From "ENG-13, Locating and Setting Engine to Top Dead Center (TDC), Cylinder 1"
Originally Posted by Clarks-Garage
NOTE
When setting the engine to TDC on the compression stroke for cylinder #1, you must realize that the crankshaft rotates twice for every single rotation of the camshaft. So, if you simply set the crankshaft to TDC without looking at the position of the camshaft, you may actually be at TDC on the exhaust stroke for cylinder #1. So, after you get the crankshaft (by flywheel indication or by checking actual piston location), check the camshaft sprocket to make sure the camshaft alignment mark is at the TDC position as well.
When setting the engine to TDC on the compression stroke for cylinder #1, you must realize that the crankshaft rotates twice for every single rotation of the camshaft. So, if you simply set the crankshaft to TDC without looking at the position of the camshaft, you may actually be at TDC on the exhaust stroke for cylinder #1. So, after you get the crankshaft (by flywheel indication or by checking actual piston location), check the camshaft sprocket to make sure the camshaft alignment mark is at the TDC position as well.
05-10-2009, 07:59 AM
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I don't see how you can fault Clark's instructions in this instance.
From "ENG-13, Locating and Setting Engine to Top Dead Center (TDC), Cylinder 1"
I can't see how you can explain it much clearer than that. Clark's Garage is not perfect, but all of the criticism I've heard of late (and, interestingly, I've only heard this of late) seems to be from people with apparent reading comprehension problems.
From "ENG-13, Locating and Setting Engine to Top Dead Center (TDC), Cylinder 1"
I can't see how you can explain it much clearer than that. Clark's Garage is not perfect, but all of the criticism I've heard of late (and, interestingly, I've only heard this of late) seems to be from people with apparent reading comprehension problems.
Specifically, the note you quoted about the camshaft sprocket is omitted from the Acrobat version. I'm guessing someone edited the html page to include that info but never updated the Acrobat document.
Also, I'm pretty confident in my reading comprehension abilities, but thanks for the check up.
-Karl
