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CamoKing

Cam sprocket /valve position disagreement??

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Morning, campers...I am at the point of returning the head to the block! on this '82, 720, Z22.  It has been months since I tore into this job.  I did paint the timing chain link and corresponding sprocket tooth but I did not recognize or record which sprocket hole was fit on the cam pin.   I am choosing hole 2 as the likely position.  Now,  I am wondering if that       previous position was altogether correct.                                                                                                          

Here is why:                                                                                       

The pistons (block in the truck)  are @TDC --#1 and #4 are all the way up...(chain with yellow paint on wedged block)...YrAyrsT.jpg?1.....so, in the head, the valves in #1 and #4 should be completely closed tight - right?  But when I place the 'V' notch on the sprocket just right of the casting mark on the head, the intake valve in #4 starts to open.  Is this OK?Nbtzpqn.jpg?.                      UI9cwHU.jpg                                                                                  If the notch is a little left of the casting mark, intake #4 is closed.  I am tempted to install this way.   But, my gut feeling is to go with the cam in this position ------------------notch aligned with casting line....(sorry, the casting line, mid Right, is fuzzy; you can see the notch on the sprocket far left)

If it is critical to have intake #4 fully closed, my painted sprocket tooth will be between 1 and 2 links to the left of the painted chain link.

Or, I'm guessing, the intake on #4 should be opening when #1 is @TDC.  ;  making it about 5˚ BTDC???

 

 

 

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Datzenmike should know.

spckets turn to the right when running.

 

I would put the chain on with the brite links on top Sproket and on lower sprocket and should self align. or you move the cam.crank slightly till it aligns.

But ask mike.

 

 But when I place the 'V' notch on the sprocket just right of the casting mark on the head, the intake valve in #4 starts to open.  Is this OK??.     I believe yes. If you have a Japanese chain the brite link will determine the true timming long as you set it on the dimple number on sprocket. 1 2 or 3. Most like 2 is used.

Edited by banzai510(hainz)

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Thanks, Hainz...I can't move the chain.  It is sitting on the 'wedge block'.  I have not taken the timing cover off so no access to the crank end of the chain.   I do NOT want it to drop.

I did notice that there is a bright link about 6 links down to the left of where I have my painted link.  I will try to add some images to be clear.   Probably should just put it back the way  I found it.

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yes put it back the way you found it

so when you removed the chain off the cam sprocket hopefully you painted that link where the dimple went.

 

get the spocket under the chain with the marked link on the sprocket dimple. I will assume youll put the bolt thru sprocket and try to get on cam dowel. however sometimes youll have to rotate the cam to the right to induce slack on the tight side(right side) to get the sprocket up high enuff to get the bolt to go straight in.

Edited by banzai510(hainz)

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(I can't upload to Imgur for some reason-F*!'in web ):   But anyhow,  Yes the painted link/tooth correspond to the V notch/dimple on the sprocket 2 hole.  I guess this is the placement.  All this sweating for nothing?  Still, it seems like the intake valve on 4 comes really close to 'interfering' with the piston.  Maybe that is just the way it is.  However, FYI, in re-working this head, I found all 4 intake valves slightly bent.  Bought new intake valves.  Wondering why this happened and trying to eliminate the chances of this happening again.

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Like I said wait till Datzenmike chimes in on this or other Z motor guys.

the number 4 clylinder is going to go downward as the intake valve is opening.

Z motors run a lower BTDC  timming I believe also like 5deg or so.

 

what I do is put the timming set together and use a breakerbar and rotate the motor clockwise one full turn to TDC on the crank and then look at the cam setup if looks correct.  Mike said there is no real notch to go by on Z series heads as a reference like a L motor with a small dash on the cam backing plate to line up the V notch from the cam sprocket.

If off put the wedge back in and move the sprocket again.  If correct tighten everything back to spec.

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Initially, before I pulled the head, (there was no timing mark on the main crank pulley) I arrived @TDC on #1 in compression by viewing through the spark plug holes, watching the cam lobes on #1 go to '8' and '4' , and examining the distributor rotor to verify a TDC position.  I'm pretty sure on got it spot on.  

 

So, on this engine, you should expect to see any intake valve opening before the piston is heading down.  This is why it is called Before Top Dead Center timing/ BTDC.  AM I getting this right?  The point where #4 intake starts to open is a little over 1 tooth before reaching that alignment between the notch and the casting line.  Given that there are 40 teeth on the sprocket, a tooth would be equivalent to 4.5˚- confirming that the sprocket is where it should be AND I am looking a the correct timing of about 5˚ BTDC!!  (I might have learned something)

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3 hours ago, CamoKing said:

Initially, before I pulled the head, (there was no timing mark on the main crank pulley) I arrived @TDC on #1 in compression by viewing through the spark plug holes, watching the cam lobes on #1 go to '8' and '4' , and examining the distributor rotor to verify a TDC position.  I'm pretty sure on got it spot on.  

 

 

 

This won't be good enough. Eight and 4 and the rotor pointing is very rough and only for making sure you are on or near the compression stroke. Usually the timing marks on the pulley are used. Failing that a pencil in the spark plug hole and watch the piston push it up and stop and go back down again. Find the highest position but get help with this. Put it together as best you can and then start setting the TDC more accurately. After this is perfect the cam position can be checked and if needed, adjusted.

 

#1 valves will be closed on the compression stroke but #4 is just finishing the exhaust stroke and beginning the intake. At TDC exhaust is almost closed and the intake just opening. They are both very slightly open and this is called valve overlap.

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"Put it together as best you can and then start setting the TDC more accurately. After this is perfect the cam position can be checked and if needed, adjusted."

 

Thanks, Mike.  I think I follow.  But, I need to be sure of the procedure in detail.  Is it like this:

1)   Do the 'pencil' test for TDC.

2)   Check the cam position by looking at the relative position of the sprocket notch to the casting mark on the head - right?                                                                                                         3)   If it is not in-line or just a little to the right, take the chain off, rotate cam until the optimum point is reached, wrestle the chain back on.

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