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304 v8 timing chain / tension ??

GRPAVL

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Finally got my stuborn crank bolt out last night and got the timing cover off.

Q1) I notice there is no tensioner on the vn 304 ... is this correct?

Q2) How much slop should there be on the chain?

Q3) does anyone know the specs or how to check if it needs to be replaced?


I have pics if it will help. will upload later today.

Q
 

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1. no tensioner.

2. not a lot

3. If there is enough slop to be concerned about it, change it.


If your just changing the timing chain, wind the engine over until the timing marks line up, cyl 1 is TDC and the dizzy rotor is pointing to the number 1 cylinder post on the cap, that way your 100% certain everything is where it should be before removing the old timing chain.
 

VR38

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Agree with above, there should be no noticeable slop (stretch) in the chain.
Lock the crank and wind the cam in the direction of rotation, there should be a little pick up off the slack from the trailing side but no actual movement in the chain links themselves on the leading (driving) side.
 

GRPAVL

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no tension


tension


from what you said above im thinking i might change it.

when I turn my crank however the dot on the crank never seems to line up with the dot on the cam gear ?? In the above images the #1 piston is tdc (i dont have dizzy in at the mo)

help
 

VR38

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The Holden timing chains are fitted with the dots on crank sprocket and the cam sprocket set at 3 O'clock.
The timing chain is fitted so that the light links on the chain line up with each dot.
There will be 9 links between the dots (including the dots), usually the shiny links on the chain will align with the dots every 4th revolution, being a 4 stroke motor.
 

GRPAVL

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what you say makes sence to me.

I have added some markings to my original pics above.

I was 180 degrees out. so I gave it another crank and here is what i ended up with. The cam spot is about 3pm but the crank is down about 4.30pm. There is 9 links between the two (but not the silvers no matter how many cranks I give it.)

Q
 

shifty6

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The Holden timing chains are fitted with the dots on crank sprocket and the cam sprocket set at 3 O'clock.
The timing chain is fitted so that the light links on the chain line up with each dot.
There will be 9 links between the dots (including the dots), usually the shiny links on the chain will align with the dots every 4th revolution, being a 4 stroke motor.
actually, a 4 stroke motor takes only two revolutions to complete the 4 stroke cycle, so the links and dots will align every two turns, provided you begin at TDC #1 firing.
 

VR38

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actually, a 4 stroke motor takes only two revolutions to complete the 4 stroke cycle, so the links and dots will align every two turns, provided you begin at TDC #1 firing.
Sorry, blond moment, racking my brains over the timing marks. Yes 2 complete revolutions completes the 4 stroke.


To the OP, I would not worry too much about the shiny links re aligning, so long as the valve timing is correct, meaning the valves move at the corresponding time to the crank.
This is what "degree the cam" is.



Forget the tensioner, it was deleted, it is on the wrong side anyway.
 

GRPAVL

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vr38 - any chance of a bigger image, cant really see much on that one.

for the silver links - I fugure who ever installed that chain just didnt line it up with the marks so wasnt too concerned. It was a going engine before i stripped it down so i guess it has to be right. New chain arrives this afternoon so will try get into it tomorrow before work.

Q
 

VR38

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tension


from what you said above im thinking i might change it.
This is not checking stretch, maybe I can try explain it again, lock the crank so it can NOT move and then using a socket rotate the cam in the direction of rotation, the slack you have pictured here will take up but there should be NO NOTICEABLE TAKE UP BETWEEN THE LINKS THEMSELVES. ( caps for clarity, not yelling).

The slack you have pictured maybe due to a stretched chain, as well as putting the bottom mark past 4:30 but without testing the chain as above it could be due to several other reasons too.

1, incorrectly indexed cam (the pin at the front that locates the cam sprocket indexed incorrectly from manufacture) Degree cam to check.
2, line bored block (moving the crank closer to the cam, needing an aftermarket sprocket set to correct)..

What you have pictured above does not look excessive to me, just check for stretch and if possible, degree the cam.
 
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