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Dazman1360

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I know there is a description in the WSM on how to set cam timing without any timing mark, but wanted any recommendations on setting it more accurately using a 360 degree timing wheel & dial test indicator.

Given there is potential the timing marks on the engine are not accurate, there is around 10DEG of dwell on the piston when raised, some dwell also with valves at full lift and I have a duplex timing chain kit so no timing marks, I want to re-check my cam timing for my own piece of mind (and sanity).

There's plenty of info out there I know, but to hear from someone that has used this method on one of our engine just adds reassurance.

Many thanks

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The "equal lift at TDC" method you mention in your other post should work just fine for a symmetrically ground cam (which I think that is) and that would count as the generic method.  Most important point is to check that TDC is in fact TDC!  Best way to do that is with a "piston stop" and a degree wheel.  The piston stop can be a modified spark plug body with a bolt in it which allows the engine to come nearly but not quite to TDC by stopping the piston coming any higher.  You note the degree wheel position then turn the engine the other way until reaching that stop again.  TDC is exactly 1/2 way between the marks (the short distance, 1/2 way the long way will be BDC).  You could even just scrape the marks on your pulley and measure between those.  Small crank 1300 is a pretty much 1mm/degree of circumference IIRC.

Nick

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Here's a pic of my piston stop, and of it fitted before the studs are put in  - if you leave them in, then just drop the stop over them and make up a spacer, or a washer state  so that the stud nuts can hold it down.

Used exactly as Nick says.

John

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Nick_Jones wrote:
The "equal lift at TDC" method you mention in your other post should work just fine for a symmetrically ground cam (which I think that is) and that would count as the generic method.  Most important point is to check that TDC is in fact TDC!  Best way to do that is with a "piston stop" and a degree wheel.  The piston stop can be a modified spark plug body with a bolt in it which allows the engine to come nearly but not quite to TDC by stopping the piston coming any higher.  You note the degree wheel position then turn the engine the other way until reaching that stop again.  TDC is exactly 1/2 way between the marks (the short distance, 1/2 way the long way will be BDC).  You could even just scrape the marks on your pulley and measure between those.  Small crank 1300 is a pretty much 1mm/degree of circumference IIRC.

Nick

I now have the specific instructions for the camshaft, so will now at least be able to check with some confidence I know what I'm looking for.

Thanks for the Piston Stop idea with the spark plug, I will use that.

JohnD wrote:
Here's a pic of my piston stop, and of it fitted before the studs are put in  - if you leave them in, then just drop the stop over them and make up a spacer, or a washer state  so that the stud nuts can hold it down.

Used exactly as Nick says.

John


John - good tool, but the head is on my engine so will use Nick's method I think.

Thanks to both.

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Best have the modified spark plug stop the piston a fair way down from the top of the stroke as with John's stopper.

If near top of the stroke there is greater rotation of the crank per unit of piston rise and this, combined with the greater mechanical advantage available nearer the top (making rotational force applied to the crank more critical), can cause less accuracy.

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7017 wrote:

John - good tool, but the head is on my engine so will use Nick's method I think.


The head is on?   Is it just that you have changed the chain, and lost the timing?
Because if you have a new cam, you MUST fit new followers and the head MUST come off.

JOhn

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JohnD wrote:


The head is on?   Is it just that you have changed the chain, and lost the timing?
Because if you have a new cam, you MUST fit new followers and the head MUST come off.

JOhn


The engine is completely rebuilt, new cam, followers etc. etc. I have fitted a duplex timing chain kit, so no timing marks at all.

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If - IF - you haven't moved the crank or cam shafts since removing the singlex chain and sprockets, you need merely fit the duplex.    Big 'if' though!   Argument for doing this sort of thing in one session.

Good luck!
John

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