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Finding TDC cylinder 1 (easiest way)

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Old 07-27-2006, 01:44 AM
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Default Finding TDC cylinder 1 (easiest way)

I know some of the tools you can use but idk what I should use....whats the best tool/easiest way?

I know what a piston stop does, but how do you know that the piston is at TDC? Does the stop make a noise or move or what? I heard putting a pencil in there but the seems risky...and also putting your finger over the plug hole until you feel vaccum, then compression (which would be the compression stroke) which seems like it can be misread..unless your feeling compression and the rotor is pointing to terminal 1 then it would be right.

Correct me if im wrong on anything I said...so whats the best way?....without taking the heads off.
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Old 07-27-2006, 08:28 AM
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I usually stick a tiny screwdriver in the spark plug hole and feel it out as I turn the motor over with a breaker bar. Don't leave it shoved in the hole or you risk smashing the screwdriver between the piston and the cylinder head obviously, just use it to "feel" the piston's position. May or may not be the "best" way, but its quick and easy for me.
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Old 07-27-2006, 10:58 AM
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Default Finding TDC

Are you trying to find TDC or are you looking for TDC in the compression stroke as in when #1 spark should fire? As you probably know, Top Dead Center occurs twice during a 4 stroke engines rotation.

You can find TDC by pushing about 2 feet of clothesline rope into the cylinder (leave a few inches sticking out) and rotate the crank, only by hand or breaker bar, clockwise until it stops. The rope is used instead of a piston stop, but the procedure is the same. Mark the timing cover with a reference mark, and place a mark on the balancer aligned with it. Then rotate the crank counter clockwise until it stops and again mark the balancer where it lines up with the reference mark on the cover. Exactly 1/2 way between the two balancer marks will be TDC. Make a new mark at the 1/2 way point and erase the previous marks on the balancer. The reference point on the cover and the new mark on the balancer give you TDC.

After you find TDC, you can determine the compression stroke by having someone push their thumb over #1 spark plug hole while you "tap" the key to crank the engine a little at a time. When their thumb is blown off the spark plug seat, and the TDC marks line up, you have found the top of the compression stroke.

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Old 07-27-2006, 11:53 AM
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Originally Posted by Brains
I usually stick a tiny screwdriver in the spark plug hole and feel it out as I turn the motor over with a breaker bar. Don't leave it shoved in the hole or you risk smashing the screwdriver between the piston and the cylinder head obviously, just use it to "feel" the piston's position. May or may not be the "best" way, but its quick and easy for me.
I use the same method with no problem.
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Old 07-27-2006, 12:16 PM
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ive used the screwdriver method too, and it worked great. this was on a small honda engine, but should work the same.
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Old 07-27-2006, 12:48 PM
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FWIW, to know if you're on the compression stroke or the exhaust stroke is easy -- if you're coming up on TDC and both valves on that cylinder are closed, its the comp. stroke. If the exh. valve is open, its the exh. stroke.
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Old 07-27-2006, 12:51 PM
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well im going to changing the distributor in my car soon...so the eaisest way would be if I am feeling the piston with a screwdriver in #1 cyl....and the rotor is pointing to the #1 spark plug terminal on the distributor?
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Old 07-27-2006, 03:14 PM
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... and both valves are closed...
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Old 07-27-2006, 05:46 PM
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if ouy dont have the valve covers off do the thumb trick. you'll fell te presure trying to escape. dont let the "thumb blowing off the seat" line scare you. its nothing violent you can just fell the air tring to come out. if you use the screwdriver and your rotor is pointing at #1 you can still be 180 degrees off because you could be firing on the exhaust stroke. thats why you gotta use your thumb.
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Old 07-28-2006, 12:23 PM
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Originally Posted by leonpiper69
if ouy dont have the valve covers off do the thumb trick. you'll fell te presure trying to escape. dont let the "thumb blowing off the seat" line scare you. its nothing violent you can just fell the air tring to come out. if you use the screwdriver and your rotor is pointing at #1 you can still be 180 degrees off because you could be firing on the exhaust stroke. thats why you gotta use your thumb.
I do the same thing right there. It'll let out a "whoosh" of air and it'll be at top dead center.
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Old 07-28-2006, 01:46 PM
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I use a 1/4" ratchet extension. I had a screwdriver break off one time because my friend turning the crank didn't get stopped fast enough. The screwdriver works but I'd rather be safe than sorry.
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Old 07-29-2006, 05:46 AM
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If you are just changing your distribitor, just remove the # 1 plug and turn the motor over by hand till you dont feel any more air blowing out. this will be cloce enough to change out the dist. but if you are degreeing a cam, use the rope meathod or better yet, use a piston stop and find tdc the same way the rope meathod is decribed..
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Old 08-19-2011, 07:53 PM
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Unhappy what's the easiest way to find top dead center

Hi folks!
However I've been participated into many other BMW forums, but this is my
1st time here in this forum, after reading a few thoughts of you here...
I found that most of you are pretty much acknowledge of the engine.

As I'm ready to perform a "Timing Belt" job on my (2000 Mitsubishi Galant ES 4cyl. that recently had the head rebuilt due to timing belt failure while driving.
I'd love if you guys could help me with some good ideas on how to set the
top dead center position before I can even install the cylinder head.

My concern is: wouldn't it be easy, before installing cylinder head to just
1-turn the crankshaft engine so, #1 piston could go all the way up

2-And turn camshaft cylinder head to his timing mark, by the way top
dead center is reached or not? So I can begin installing new timing belt...
Any help would be greatly appreciated!!!
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Old 08-21-2011, 09:09 AM
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The "feel w/ a screwdriver" method is not accurate. The dwell time of the piston @ TDC is a source of a possible error. The positive stop method is much more precise....
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Old 08-21-2011, 05:41 PM
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Unhappy confused about set-up top dead center!

Now, I king of confused about this method using a *Screw driver
to set the engine/cylinder head on top dead center. I just installed
my cylinder head today that was rebuilt due to timing belt failure while driving.

But tomorrow will be the timing belt job and this is the biggest challenge
for me because things can go wrong if not set-up properly.
This is my biggest fear because after paying nearly: $500 dollars
to have the entire cylinder head rebuilt, I really don't want
to go over this issue again.. By the way, the head is installed now,
so I will need further help on set-up the dam timing belt hopefully
to have my car started once again, after not running for the last 3months.

(2000 Galant ES 4cyl.)
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Old 08-27-2011, 05:25 AM
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I always just stuff a paper towel in the spark plug hole. Dont cram it in there just enough to hold it. Turn the engine over until that baby pops out. This is when you know youre on the compression stroke. Line up the timing mark and drop in the distributor. This may not work if you turn the engine over like an old man. You need to get on that breaker bar and turn it over enough to give the cylinder a little pressure to pop the towel out. If you baby it it may not be enough to pop it out.
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Old 08-27-2011, 01:58 PM
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Unhappy timing belt help

wonder why alot of us can't figure out how to properly set-up
a simple timing belt on our cars. That procedure may look easy after all,
but it's the tricky method about it: put it on top dead center, set-up
timing belt, compression stroke...bla, bla, bla... that makes the job even
more difficult and confusing as it appears to be.

Starting on me 1st, I unplugged everything, removed the entire cylinder
head and sent it to machinery so, it could get rebuilt after timing belt failure while driving. 3 days later, I hooked up everything together and installed the
entire cylinder head all by myself again...But unfortunately the one's that
appears to be easy to set-up, which is the timing belt becomes one of
the most fear for me now. I cannot see myself coming this far...and now
paying mechanic for just a timing belt. This is why I'm seeking as mush help
as I could from you guys.

(2000 Galant ES 4cyl.)
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Old 08-28-2011, 10:43 AM
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Mysweetx5 just set your crank to the crank mark on the motor line up your cam mark (s) to where they need to be with int/ex valves closed on number 1 cyl . Your crank will not be 180 out the only think that can be 180 out is your cam but if u line up your cam marks are lined up and valves closed u should be good to go once u get the belt on spin it over by hand 5-6 revolutions makes sure all your marks as far as cam crank line up and u should be good to go. If your belt has timing marks on it those will not line up again after spinning it those are just for initial set up there is a formula to figure out how many turns it takes to line up belt marks but its not needed
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Old 08-28-2011, 03:22 PM
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Wink

Thanks alot spaulding!
Your guidelines are much understanding for me to catch-up!
I will go with your description instead, because I'm so desperate to have
this vehicle running so bad, after broken down while driving on the hwy 3months ago.

I had to pay:$425 dollars to get the cylinder head rebuilt, and now
everything is back on track, I managed to install the cylinder all by myself.
However, my biggest fear was: set-up the timing, if it wasn't for the timing belt,
my car would have been running by now.

Once again Thanks for your help, I'll try it by tomorrow...
Appreciated your inputs.
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Old 08-28-2011, 06:51 PM
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Originally Posted by spaulding View Post
Mysweetx5 just set your crank to the crank mark on the motor line up your cam mark (s) to where they need to be with int/ex valves closed on number 1 cyl . Your crank will not be 180 out the only think that can be 180 out is your cam but if u line up your cam marks are lined up and valves closed u should be good to go once u get the belt on spin it over by hand 5-6 revolutions makes sure all your marks as far as cam crank line up and u should be good to go. If your belt has timing marks on it those will not line up again after spinning it those are just for initial set up there is a formula to figure out how many turns it takes to line up belt marks but its not needed
Hi spaulding!
just a quick question I wanna ask you before proceed ahead on the timing job.
should I line-up each section to their mark 1st before I put the new belt?
Or how is it going to be possible to line-up each section to their mark while
the timing belt is on? How will I know when all valves are closed inside?

(2000 Galant ES 4cyl)
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