TDC and cam timing marks

[ilikespeeding]

So, when my cam timing marks align, that means Im at TDC on #1 right?

...pretty stupid question, I know.

 

[Hollywood77]

Kinda. When ALL the timing marks align, you'll be good. Don't forget to referench the indexing mark on the oil pump sprocket also.

I'm pretty sure I'm correct there. I'm two weeks from changing my timing belt and installing my balance-shaft eliminator kit, otherwise I'd totally be able to set you straight, with 100% certainty.

 

[VTEC_THIS]

Assuming your pistons are in time with them, then yes.

 

[vanilla gorilla]

This is what I do to make sure I'm at TDC,
I pull the spark plugs so I can turn the motor over by hand.
Then I put a long screwdriver and stick it down into the #1 cylinder spark plug hole.
Then I turn the motor over by hand at the crank until the screw driver rises and peaks.

 

[DSM1G90]

Don't forget to refresh the indexing mark on the oil pump sprocket also

..and if you're gonna keep the balancers in the block, the oil pump sprocket has to be a certain way with the mark. For if you get the sprocket off 180*, you've got some serious vibration there as the results.

You notice that the mark is at the 10:00 o-clock position on the block. Rotate the sprocket so the pointer on the sprocket is at the "noon" position. If the sprocket rolls clockwise, the balancer is 180* off mark. Rotate the sprocket again to the "noon" position and the sprocket should roll anti-clockwise. This will get the balancer in phase with the crank when you align up the two marks - the block and on the sprocket.

until the screw driver rises and peaks.

I've used a long soda straw so I don't ding up the sparkplug hole in case the screwdriver wants to tweak on you when it comes up to peak.

 

[dave99gst]

This is what I do to make sure I'm at TDC,
I pull the spark plugs so I can turn the motor over by hand.
Then I put a long screwdriver and stick it down into the #1 cylinder spark plug hole.
Then I turn the motor over by hand at the crank until the screw driver rises and peaks.

Thats what I would do also. Its the easyest way to explain and reproduce it.

 

[bmoha2]

of the four which is number one?

 

[Black99gst]

driverside of the car... far left (right hand side if your looking at the motor from the front of you car... opposit if the intake filter... opposit of the trans, same side as the belts

no mistakes

 

[bmoha2]

I'm trying to get over my fear and do the timing belt and balance shaft removal. I've done everything else on the car myself. Might as well.

 

[vanilla gorilla]

Its not hard. Its overwhelming at first if you've never done it before, but once you do it once, its cake.

 

[Hollywood77]

I'm trying to get over my fear and do the timing belt and balance shaft removal. I've done everything else on the car myself. Might as well.

No doubt!! I just HATE messing with timing belts and cam gears. I've done everything else myself too, but I'm kinda sweatin' bullets about this whole timing belt/balance shaft job that I've got coming up.

I'm glad I'm not the only one.

 

[Laysher91]

WHOA! Slow down...the number 1 cylinder comes up to TDC twice per engine cycle; on the compression and exhaust stroke. You want it to be at TDC of the compression stroke which means the timing marks will line up and the rocker arms will be loose. You can do the screwdriver trick but make sure by taking off the valve cover and confirm that the rocker arms are loose. If you have it at TDC of the exhaust stroke on clyinder 1, cylinder 4 will be at TDC of the compression stroke.

 

[vanilla gorilla]

Your making it more complicated than it has to be.

When you put the crank at TDC, the cams will either line up where they should or be 180 degrees off.

 

[chris90gsx]

I always wondered the significance of setting TDC for #1 on the compression stroke. I was reading through a manual for another vehicle yesterday as I'm helping a friend out with her car, and it showed how to actually set TDC for #1 on the compression stroke. Is it really that critical to have #1 at TDC on the compression stroke opposed to the exhaust stroke?

That said, I've always just set #1 at TDC regardless of whether it was on the compression or exhaust stroke whenever doing any sort of relevant work requiring this (i.e. timing belts, valve adjustments, etc.), and I've followed this practice for a host of different vehicles, of course DSM's being the mainstay, without any issues.

 

[DSM1G90]

I'm sure that when the first internal combustion motor was invented, that valve timing began with No.1 on compression - as mentioned with the crank in this position, all valves are closed.

Course, I remember when I did my first "chain" (doing V8's at the time) - take out the radiator, water pump, crank pulley, timing cover and slide tensioner, new sprockets and chain, align the crank and cam to where the marks faced each other (no.1 at compression) and do the sprockets and chain.

Doing belts, esp the SOHC's were a snap to do. DOHC's - everything has to be presice.. esp with a 4G63 motor being the interference motor. I did my DSM right after I bought it - took half the afternoon replacing everything, belt related, on the front of the motor and got it great the first time.

 

[chris90gsx]

But what does it matter if you set TDC on exhaust versus compression stroke? As long as everything aligns properly I do not see any issues. As I stated earlier, I've never checked to see if #1 was at TDC on the compression stroke. I simply just set #1 at TDC, whatever stroke it happened to be on. I've done this countless times for timing belts on DSM's and other vehicles.

Anyone have any input as to the significance of #1 set to TDC on the compression stroke versus the exhaust stroke?