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timing marks


dwd

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Hello all, I am trying to work out which ignition timing mark is which. On the bottom dia it says ATDC is the leftmost mark & BTDC is the rightmost mark. On the dia with the single pointer (LR777) which is the one I have on my series, there is no indication where ATDC/BTDC is. Can anyone tell me where BTDC is on this pulley??hash=d0d7bbfcebb0b0016605093871a57f4e

timing you need to know copression ratio.jpg

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Hi

With your set up the right hand most pointer (should be slightly larger ) on the plate is TDC , as is the notch on the crank pulley . The 6 degree BTDC is the left point on the plate .

What Series do you have ? out of interest :) some pic's are always good too

cheers

Steve b

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  • 3 weeks later...

Sorry for delay in replying, mine is series 111 petrol, hard top. I am still confused as when I enlarge the pic of timing marks it seems that 6 deg' BTDC is to the right of the pointer ie it is the furthest to right of the marks shown

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On diagram 0878 and IRA55A, 6 degrees BTDC is the left most peak,  align the crank pulley notch with that. 3 degrees before is middle peak and TDC is right peak.  6 degrees BTDC should be fine for 7 or 8.1 compression engines, on unleaded (UK RON 95).

If setting dynamically, i.e with engine running and a strobe light, remove vacuum pipe from dizzy and block the end with a small bolt. Make sure rpm is under 650. Before you do anything with the timing, make sure the contact set gap is correct, if you have a dwell meter, check dynamically - should be 52-57 degrees dwell for a Lucas 45D4 type dizzy.

Ignore diagram 0693 which is the 6 cylinder.

Edited by simonb
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  • 1 month later...
  • 2 weeks later...
On 1/15/2020 at 5:57 PM, simonb said:

The pointer in the last photo is at 4.5 degrees ATDC, try setting the timing dynamically so that the pointer aligns with the top line, with the vacuuum pipe removed from the dizzy and and its end blocked off.

Again sorry for delay, will try what you say with vacuum disconnected. So the pointer on the top line would make it the furthest BTDC mark, is that correct. Rgds DW.

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There do seem to be more timing marks than normal on the pulley, but I suspect they are like this:

lqXSV0.jpg

Providing you are 3 or 6 degrees BTDC, you will be fine, best to set with the engine running (vac pipe plugged) as this will even out the backlash and wear in the distributor and its drive. When you have it about right, the idle speed will sound more even, and may speed up a bit. Too far either way and it will slow down, too much ATDC and it probably won't even start.

Edited by simonb
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14 hours ago, simonb said:

There do seem to be more timing marks than normal on the pulley, but I suspect they are like this:

lqXSV0.jpg

Providing you are 3 or 6 degrees BTDC, you will be fine, best to set with the engine running (vac pipe plugged) as this will even out the backlash and wear in the distributor and its drive. When you have it about right, the idle speed will sound more even, and may speed up a bit. Too far either way and it will slow down, too much ATDC and it probably won't even start.

many thanks, a picture tells a thousand stories, now I can see what I am aiming for, Rgds DW.

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The pulley turns clockwise when viewed from the front of the vehicle. This means the timing marks in your picture (from the top) are 6 degrees AFTER  top dead, 3 degrees AFTER  top dead centre, Top dead centre (TDC), 3 degrees BEFORE top dead centre, 6 degrees BEFORE top dead centre. On modern unleaded these engines run well at 6 to 10 degrees BTDC. Hope this helps. Regards, Diff.

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