Healey3000

TDC and the 02again crank trigger wheel

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Hi,

 

When the engine is at TDC, where does the crank wheel line up with the TDC pointer, toothwise?  Mine has the pointer lining up with the first clockwise tooth after the gap.  I set TDC by lining up the cam sprocket mark with the oil spray bar.

 

Here's the mystery - I placed a white paint mark two and a half teeth further clockwise after the first tooth.  Since the wheel has 36 teeth, each tooth is ten degrees.  My paint mark should therefore be at 25 degrees BTDC, right?  With the engine running at 1400 RPM, I simply can't find the mark.

 

Thoughts?  I have not tried to correlate with the "ball" on the flywheel as it's a real pain but since the engine runs, the timing is clearly in the correct range.  I must be missing something pretty simple.

 

Thanks!

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Funny but I think the missing tooth is tdc. I have it on my car and can’t remember. 

 

John

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If their is not a distinct timing mark on the crank pulley, mark one. Just make sure that you make a pointer or fixed mark on the front timing chain cover, that lines up with it.
I have always used the OT line and the Z ball on the flywheel for all my timing as it’s easier, for me and its fixed known mark.


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Usually the missing tooth passes the pickup before the crank comes to TDC.

 And usually there is a software entry to designate how many teeth after the missing tooth passes the pickup when the crank is at TDC.

And usually there is enough crank turn after the missing tooth passes the pickup to allow for maximum advance to not occur in the space of the missing tooth.

And final setting is with the timing light shooting at the TDC mark (and the only timing mark left to shoot is on the flywheel on the M10).  On my system this is done with the injectors disabled and the engine cranking.

 

The keyway in the hub/crank is at crank TDC when the keyway is in line with the cylinder centerline.

Edited by jimk

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Hi Jim,

 

I'm still using my carb, as I'm doing things in stages, but the VR sensor does indeed see the gap at 90 degrees BTDC.  There is no way to mess up orientation of the trigger wheel since it's keyed to the crank so I'm sure all is well there.

 

The real mystery is why I'm not seeing the timing mark at 25 BTDC.  It should line up with the pointer.  It's almost as if I have the inductive pickup on a cylinder other than #1.

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What type of ignition are you using? If your using a wasted spark set up it will be double as the coil fires on two cylinders at the same time. If you have a 2 cycle switch on your timing light, try that setting and see what happens.


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23 minutes ago, Schnellvintage said:

What type of ignition are you using? If your using a wasted spark set up it will be double as the coil fires on two cylinders at the same time. If you have a 2 cycle switch on your timing light, try that setting and see what happens.


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Hi,

 

I'm using a crane XR7000 (or is it 3000?) with my otherwise stock distributor and carbs.  No wasted spark.  I'm tempted to try the inductive pickup on the other cylinders to see if the mark shows up.

 

There are no switches on my timing light - perhaps I have a bad timing light that has a lot of delay in it.  I can't think of any other scenario that would explain what I'm seeing.

 

Thinks.

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90 degrees before TDC is correct for the 02again trigger wheel and mount.  You'll need to set your trigger offset to that.

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Remember, the important part is the missing tooth relative to the sensor that's important.  Where the missing tooth and/or sensor are with regard to the TDC pointer is entirely unimportant as far as the electronics systems are concerned.  But I think it sounds like you have it 'right' if your plans are to go to wasted spark in the future.  EDIS (what I believe the 02Again setup was designed for) should have the missing tooth positioned nine teeth (or 90 degrees) in front of the VR sensor when the engine is at TDC.  But if you're running off of your old Crane ignition, using the distributor, and then strobe the wheel, I would expect the mark to be at 90 degrees plus whatever timing you're actually running at.  So for example if you car idles at 12 degrees BTDC, then at idle the timing light would show the missing tooth on the wheel at 102 degrees in front of the VR SENSOR.  Is this how you have things running currently?  For further details on EDIS see here, and feel free to PM me if we need to dive a little deeper on the subject!

http://www.megamanual.com/ms2/EDIS.htm

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Oh, and FWIW, my missing tooth did end up approx the TDC mark when I hung the VR sensor off of one of the waterpump bolts.  Keep in mind though I homebrewed this prior to the 02Again parts being available, so yours won't be exactly the same, but I expect they'll still be pretty similar.

783096831_2012-09-2418_26_46.thumb.jpg.f9e24514cadf8ba96498da6f307102d7.jpg

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That system must certainly be limiting if the installation of the wheel needs to be in an exact spot and the software cannot accommodate a zeroing adjustment.  People build these wheel installations with less than perfect accuracy.  I would think the efi system mfr has accounted for it.

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2 minutes ago, jimk said:

I would think the efi system mfr has accounted for it.

Yep, every engine management system that I know of has a way to set/adjust the trigger offset in order to fine tune things after installation.  The one reason you would still want to have an EDIS system installed at least 'close' to the right initial position however is so that it will still function in limp home mode if communication with the engine management system is lost.  It can still run stand-alone and will default to 10 degrees BTDC as a sort of failsafe which, although I've never really used or needed it, I still think is kinda nice to have.

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While the missing tooth sits around TDC, the sensor is several teeth before that (I can't remember the number of teeth but it works out to 90 degrees.)

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2 hours ago, AustrianVespaGuy said:

The one reason you would still want to have an EDIS system installed at least 'close' to the right initial position however is so that it will still function in limp home mode if communication with the engine management system is lost

I erroneously assumed that the system being installed was a full blown efi system, fuel and ignition.  Dealing with a production EDIS limits things to what the Ford parts need.

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Hi,

 

Thanks for the thoughts but I should not have mentioned the VR sensor as it has taken us on a bit of a tangent.  I'll try and restate the issue and hopefully, I've just done something dumb and correctable.  Note that the VR sensor plays no part in this as I'm still using my Weber carb and the same distributor ignition as before.

  • I set the engine to TDC #1 by means of the cam sprocket mark
  • I noted where the pointer lined up on the crank wheel
  • I made a mark at 25 degrees BTDC on the crank (two and a half teeth)
  • With engine running, vacuum advance disconnected, 1400 RPM, inductive pickup on plug #1, I cannot see the timing mark anywhere

The attached image shows these two positions (ignore the keyway, etc. as I used a stock image).  These are the things I can think of:

  • Cam sprocket lied to me.  I know the head has been replaced at some point on this engine.
  • My timing light is misbehaving (although, I last used it several years ago on another car and it seemed fine)
  • Cylinder #1 isn't actually #1 :)

My next steps:

  • Re-verify #1 TDC but this time, also confirm the flywheel mark and check that both #1 valves are loose
  • Find the flywheel ball and compare against my 25 degree mark
  • Try another timing light
  • Shrug, and ignore the problem since the engine is running.  No, my OCD won't allow that.

Thanks!

EDIS.png

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