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I Need Help making Wood block for adjusting timing chain stretch!


Larry 73Z

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Larry, I believe the wood block you are talking about is intended to keep the timing chain secured (by wedging it in place) and properly indexed to the crank drive sprocket during partial disassembly. There is an automatic chain tensioner that addresses timing chain stretch, located on the non drive side of the timing chain, in the front aluminum casting. Some of the after market repair manuals provide details on its fabrication. Is this help at all?

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Larry, I believe the wood block you are talking about is intended to keep the timing chain secured (by wedging it in place) and properly indexed to the crank drive sprocket during partial disassembly. There is an automatic chain tensioner that addresses timing chain stretch, located on the non drive side of the timing chain, in the front aluminum casting. Some of the after market repair manuals provide details on its fabrication. Is this help at all?

It's true that the tensioner addresses timing chain stretch but when it has stretched too much you have to move the timing chain sprocket to the next of the three possible positions. The main reason that the block is needed is to keep the tensioner from coming out. Keeping the chain properly indexed on the crank sprocket is also accomplished with the block.

For the original poster: if you're planning on doing this job yourself you presumably what either a factory service manual or one of the aftermarket manuals to step you through the process. These manuals should cover this very issue and even give instructions on how to make the block. I don't recall but the FSM may only direct you to acquiring the "special tool" from Nissan.

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The shape is simular to that of a door stop, attach a cable to it so you have something to grab when you want to remove it. I have used a section of wooden broom handle and it worked well for me. I have also seen the datsun tool on ebay quite often for around $7.00.

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Thanks guys, but I was hoping someone would have the actual picture so as not to have to buy one if possible. I have a picture of one but it is not clear as to if both bottom sides are tapered or not. I think I saw somewhere that the wedge is suppose to be 1 inch wide by 7 inches long and 1/2 inch thick and tapered at the end where your drive it in against the timing chain tensioner? I am not sure if that is correct and hope some can clairfy it for me.

Thanks again!---Larry

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We always used a 16" length of 1" hose to stuff between the chains. I found a plastic-handled screw driver in an engine I purchased. It had run so long that the handle had warped from the heat but the driver part did not hit anything. I guess they were just lucky and I was lucky to find it.

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Sorry if the dimensions are hard to read, I had to shrink the image to get the website to accept it.

If you copy the image to your computer, you can then enlarge the pic in MS Paint or another program to see them better

This diagram is from the bible. "How to Modify Datsun Engines and Chassis" book published by H.P. Books in 1973

EDIT: I see someone else posted while I was creating this. Oh, well.

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It's funny how the so called tools are all so different. The fact is you just need something that will wedge in tight enough to keep the tensioner from popping out. I'm a little skeptical of the hose idea but I've even seen a big screwdriver used - on the ZTherapy video. I really don't think the dimensions and/or angles are critical; just jam it in good.

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It's funny how the so called tools are all so different. The fact is you just need something that will wedge in tight enough to keep the tensioner from popping out. I'm a little skeptical of the hose idea but I've even seen a big screwdriver used - on the ZTherapy video. I really don't think the dimensions and/or angles are critical; just jam it in good.

I agee. One thing that I think is beneficial is that there be a slight taper so that it's slightly narrower at the bottom and widens out higher up so that it "wedges" the tensioner tightly.

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Doesnt even need to jam the tensioner (ie touch it), as long as it traps the chain on either side of the guides the tensioner will not pop out as the chain cannot move

Well of course it doesn't touch the tensioner. It presses on the chain which in turn touches the tensioner. The fact remains that the purpose of the tool is to retain the tensioner.

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Quick Adivce:

On the Z-therapy video, he uses a screw driver placed in there upside down, using the handle to hold tension.

Speaking from experience, I do not recommend this, in the event that you decide to remove the screwdriver after placing the cam sproket back on and the handle stays wedged and the rest of the screwdriver comes out, this IS a HORRIBLE EXPERIENCE.

Trust me on this.

:) Bri

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Well of course it doesn't touch the tensioner.

Considering there is considerable confusion around this area (someone thought the tool was for re tensioning the chain) I thought it worthwhile pointing out, because so far, non of the posts (including yours) had.

But if we are all so educated as to how to do this why is the thread 2 pages long and several differant drawings shown.

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Some folks tried to clear up if the origninal poster really understood what he was talking about. He may have just said it funny, but you do use the block to secure the tensioner, if you are going to remove the cam sprocket to move from one index hole to another to in order to adjust for chain stretch (or advance cam timing for another reason).

Some things become obvious when a person delves into actually doing the job. We're answering a question about the tool, not giving a step by step How To lesson. He didin't ask for that

One drawing from a Nissan publication, one from a Racers book, one from an Internet Parts seller. The fact that there are several different designed tools that will work shouldn't be a surprise to anyone. It's a common tool for working on OHC engines, some are more elaborate than others.

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I kept it simple, cut a piece of wood, sanded it a bit so nothing would come off the wood getting into the oil, drilled a hole about an inch or so down from the top of "tool" and looped some wire so I could remove the tool after the sporket was back on.

Not to attractive, but has always done the job and was REAL cheap...

So this would qualify and the not-so-elaborate, but oh-so-effective.

If you want the measurements lemme know.

b

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To all of those who answered,

Thanks guys for all of your thoughts and replys and pics! It is kind of funny though how there are several ways people have made those wedges different to do the same job. I guess from what I have seen here, is that the point is to make sure that the chain tensioner does not move or then the so called "fun" will begin. I just hope that I get it in there tight enough that it doesn't. Thanks again!

Larry

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