How does the JD40 cam sprocket tool work?

[Tarapoochy]

Hi all. Looking for some advice on my V12 engine.

I have it out at the moment while the gearbox is fixed and although the engine runs well there has always been a bit of a tap which sounds like it comes from the top end. While it is out I have checked the valve clearances and if anything they are a bit tight. Some are down to 10 thou. I would like to change the cam chain and set the valve clearances. Reading through the ROM it talks about fitting the JD40 tool to retain the cam sprocket. But just how does this tool fit?

There is a bracket that comes up outside the sprocket with a "U" shaped slot in it and I can see that the took fits into the groove on the shaft coming out of the sprocket centre. Does the tool engage with this bracket somehow? If not then just what does the JD40 tool do?

Any advice much appreciated.

[MarekH]

I don't think it does anything useful.

The JD40 tool is just a way of hanging up a loose chain and cam sprocket when they are not connected to the crank. A marker pen or scribe with an arrow pointing "this way up!" will do just as well.

If you start with both cam notches pointing downwards and the crank at approximately 0', undo the two most easily accessible bolts on the end of each camshaft. Now rotate the engine 360' with a spanner on the crank bolt until you have both cam notches pointing exactly upwards and the crank exactly at 0' - 1A TDC. If you don't separate the cam sprockets (i.e. don't undo the big circlip over the tiny teeth in the middle of each sprocket), then everything can only go back on one way anyway, so there is no need to worry about alignment or fixing or moving anything.

Assembly is the reverse of disassembly. With the crank at 1A TDC and the cam notches pointing upwards as per using the cam tool, do up two bolts on the ends of each camsprocket. You can then rotate the engine forwards 360' and do up the other sprocket bolts.

It's pretty hard to misalign a 5/16 size bolt and bolt hole. It has to go back on exactly how it came off and the marker pen makes sure the right holes are lined up with each other as before.

kind regards
Marek

[Tarapoochy]

Thanks MarekH. That seems to explain it then. You'd think they would have made the tool so that you could hang it on the bracket! I don't know why they didn't design it that way!

Rick

[Bob.]

Although these are homemade JD40s, this is how they are used as per the ROM. They lock the sprocket to the parking bracket.