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Old 06-19-2018, 03:52 PM   #1
zblad
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Default Can the timing be off if all marks are lined up

Alright so I got a jdm motor and had everything centered and lined up with the timing marks. When I loosened the belt pulley to replace the timing kit the two cams on the right side (drivers side) spun. I have a friend telling me that if the crank spun that it could be a 180 degrees off. Is this true? Or if I realign all the timing marks and spin the two cam shafts the correct direction will the timing be on even if the crank did spin an extra rotation? How do people rebuild a motor and do the timing? I assumed as long as all the timing marks are on that it would be fine? Please HELP
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Old 06-19-2018, 03:56 PM   #2
gabo_s13
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Just re-align the timing marks and you should be good. Hopefully there wasn't any v2v contact when they spun.
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Old 06-19-2018, 04:49 PM   #3
Bansheeboy11
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If the two driver side cams spin they can hit the valves and bend/chip them. You should put the belt back on, align everything and leak test those two cylinders to be sure nothing was damaged. If you drive with damaged or bent valves it'll destroy the seats which can either drop into the cylinder or crack/break a valve, both lead to catastrophic failure.
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Old 06-19-2018, 06:24 PM   #4
jamal
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When they spin, after you take the belt off, that is all the valves closing. They are not going to hit each other.

The thing you do need to do is make sure to turn the cams the right way in the right order, because you can have the valves contact each other turning both cams back to the correct place. Upper gear clockwise, lower gear counter clockwise.



Key thing is rotating the 2nd gear the right direction and only the specified amount. With the crank in the "set timing" position you can individually spin any of the cams all the way around without anything hitting anything else because the pistons are halfway down the bores and all the other valves are closed.
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Old 06-20-2018, 03:58 PM   #5
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Jamal is spot on. If you turn the cams the wrong way on that side of the engine you will bend valves, even so slightly it is not visible to the naked eye. It can be picked up on when valves are refaced. If you did that and run the engine it will slowly "burn out" the bent valves.

Another trap for young players is using the triangle mark on the crank to align the timing. That is the TDC mark, not the timing belt mark.
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Old 06-23-2018, 09:59 PM   #6
zblad
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Default so...

So if the timing marks are all aligned there is no way for it to be on the wrong stroke? My friend is saying that the motor could spark when the exhaust valve is open.
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Old 06-24-2018, 05:48 AM   #7
Bram
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Quote:
Originally Posted by zblad View Post
So if the timing marks are all aligned there is no way for it to be on the wrong stroke? My friend is saying that the motor could spark when the exhaust valve is open.
Id say your frind has a mild case of retardation.


The crank does 720 for 360 of cam rotation.
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Old 06-24-2018, 03:41 PM   #8
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Quote:
Originally Posted by zblad View Post
So if the timing marks are all aligned there is no way for it to be on the wrong stroke? My friend is saying that the motor could spark when the exhaust valve is open.
If you use the correct alignment mark on the crankshaft and all of the other marks line up it will be on the correct stroke. The cams on the bank that spun when you had the marks lined up are slightly open when they are on the marks. That is why they spun, and they will be trying to jump off again when you do the new belt, which is the only tricky part of this activity. You can spin that crankshaft around 100 times and put it back on the alignment mark and it will be on the right stroke.
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Old 06-24-2018, 05:53 PM   #9
00_imprezaoutback
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Quote:
Originally Posted by ripman View Post
Another trap for young players is using the triangle mark on the crank to align the timing. That is the TDC mark, not the timing belt mark.
So now when I took the timing belt off my ej251 I had the crank on the square not the triangle/arrow. When I go to put the motor back together I leave the crank on the square and line up the cams? Or have the crank on the triangle/arrow and line up the cams?
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Old 06-24-2018, 10:14 PM   #10
jamal
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The triangle is for top dead center of cylinder 1 (and 2). DO NOT USE THAT MARK TO SET TIMING. The rectangle/hash is the one to use.

Quote:
Originally Posted by zblad View Post
So if the timing marks are all aligned there is no way for it to be on the wrong stroke? My friend is saying that the motor could spark when the exhaust valve is open.
I don't know what that even means.
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Old 06-25-2018, 09:09 AM   #11
zblad
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Thank You ripman and everyone else... Just don't want to put the timing kit on and get everything back in the car and it not start.
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Old 06-27-2018, 04:51 PM   #12
Charlie-III
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Quote:
Originally Posted by jamal View Post
The triangle is for top dead center of cylinder 1 (and 2). DO NOT USE THAT MARK TO SET TIMING. The rectangle/hash is the one to use.



I don't know what that even means.
To add a little, you want the line that is stamped on the crank trigger wheel to line up with the notch on the crank sensor mount.
Do NOT use marks on the front of the crank gear for timing belt alignment.

The proper crank mark has the pistons at mid stroke, not TDC.
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