Im in the middle of doing a head gasket, i sent the head out for a valve job.. Now i read that the marking on the head and the marking on the timing chain sprocket should line up to become TDC,,,, But on the first cylinder the exhaust valve is down about half way..

Also,, how do i know when the engine is TDC?? i would imagine even half a tooth off on the timing chain will cause it to run very poorly or even damage my head.....

Also can the head and engine be adjusted with the head bolted on to the block??

Is there any prinouts someone can send me to properly time both the head and the engine.. i really only have one shot

ANYTHING WILL HELP

It'll be obvious that the #1 cylinder is TDC, by looking at the piston, then also look at the pointer for the harmonic balancer and ensure that it's pointed at the "O|T" mark.
On the cam, if you look at the ring behind the sprocket, and the front of the #1 rocker arm bridge, you should see a small indented dot on the ring, and that'll line up with the small pointer on the #1 bridge. Also the cam lobes will both be pointing up (at an angle).
To make sure aeverything is correct, after you install the chain tensioner run the engine through twice by hand and make sure these marks once again are aligned. You CAN'T be off by half a tooth, it will only be off by WHOLE numbers

Gilly

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Yes, but if the cylinder is all the way up, then it will hit the valve.. when i turned the head to TDC by using the mark on the head and the mark on the shaft for the cam the exhaust valve was half way out.. what are your thoughts?

Is the head already bolted down? The best approach, or at least the one that I used was to put number one to TDC as indicated on the Harmonic Balancer, then put the head in place without the cam. Place the cam in place with the TDC mark aligned against the mark on the front cam tower. Then gradually start the cam bearing stand bolts, a little on each bolt at a time. Don't tighten one or a pair of bolts down all the way, you could break the cam or strip the boltholes. Turn each bolt a turn or so, then the next bolt and so on, then start over again adding a turn at a time.

If you have a valve touching a piston it is not timed correctly.

Good luck,

Ok this is my situation,,

I was going to take the head off for a valve job and replace allt he gaskets,,, while removing the head i skipped the step of taking out the pin from the guide rail,, so i snapped the guide rail,,, im now awaiting shipment of the guide rail..

I have replaced the head and only tighten the head bolts hand tight to stop any debris from getting in the freshly cleaned holes,, also i have replaced the intake manifold onto the head

So i still have the front of the engine off to do the guide rail when it comes in,,, I want to make sure the Head and the engine is TDC before i torque the head down.. However i was told that even with the head tightened on i can still effectively time the engine.

What are your thoughts,, i would rather not take the cam shaft out of the head because it was just redone and lubricated and refurbished to factory spec.. any information helps me at this point

Yeah your right, the lobes shouldn't be facing "up" at TDC on a 103. Can you see the small drilled mark on the ring I was talking about, on the cam just behind the sprocket, or not? On the #1 rocker arm bridge, on the front of the casting is a small index which should point at this drilled in mark when you're at TDC, that should time it close enough. Another reference I can think of is on the front of the cam there is a pin which indexes with the sprocket. That pin should be on the right (passengers side) of the engine.

Gilly

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I lined up the mark that is in front of the rocker arm to an upraised ridge on the back of the sprocket "pulley",,, so i need to watch for a small drilled hole?

in the manual i had printed up of this forum it shows the tab to the tab

I posted a reply a few minutes ago and it seems to have disappeared, I'll try again....

Rotate the cam so the #1 lobes both face down like an upside-down "V". On the ridge on the front of the cam itself that the sprocket bolts thread into, you should see either a small dot or a definite line punched into that ridge, this is what lines up with the pointer on the #1 rocker arm bridge. It's a very definite mark, not cast into the cam but purposely put into the cam after being cast.

Gilly

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just to clarify one more thing, when you say #1 Lobe, what are you referring to exactly, thats the only part i dont quite understand...

I mean the front 2 lobes on the camshaft, these are the lobes for cylinder #1, it's all timed off of the #1 (front) cylinder.

Gilly

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I just got it!!! Awesome thanks.. I couldnt see the small drilled hole, the guy at the head shop lubricated the cam with a white grease.. but i saw a slight indent in the grease and cleared that one spot to see that VERY tiny hole, i was looking for something larger....

Now that i have the head set to TDC the only thing left is to set the engine to TDC... However i have the head on it,, someone told me that i could tell when cylinder #1 is at TDC by using a wooden dowel into the spark plug hole and observing the up and down movement, he said to wait for it to "apex" and i will know when its TDC,, does this sound like a reliable bit of information, could the timing still be off if im even slightly off? Or will the chain match up to the sprocket on the crankshaft enough to correct this?!?

You can be a little more exact by using the small pointer on the front timing cover (near the TDC sensor) and the mark on the harmonic balancer marked "O|T" The pointer should point at the line between the O and T, that's when you are exactly at TDC on #1 cylinder.
Like I said though, you want to run the engine through twice by hand after installing the chain tensioner and recheck the camshaft mark and crankshaft index to make sure you are still in time.


Gilly

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The bracket that holds the Sensor onto the block looks like it can slilde on the bolts slightly each way,, the holes in the bracket arent perfectly circular they are a little longer which would allow the bracket and sensor for that matter to not be at exactly TDC if its not in the right spot i would imagine...

also just for educational purposes only what is the purpose of the sensor mounted on that little bracket,, how does it work, what does it affect?

When you turn the crank to TDC (as observed with the markings on the harmonic balancer) you'll note that there is a small cylindrical object inserted into the balancer which is directly under the sensor. It's a small magnet. The sensor senses this magnet at each crank rotation as it passes by. The sensor passes this timing signal information to the ignition control unit, which uses it to operate the sparkplugs at the correct time. Other units use this information also, such as the tachometer and the fuel pump relay.

Gilly

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Wow thats impressive,, while i have everything off,, should i replace this sensor, whats the likelyhood that it isnt strong anymore or isnt wokring properly??