Rotor Arm 45 degrees out

PostPost by: mbell » Sun Jan 01, 2017 2:54 am

Hi,

Attempting to re start the car after engine and gear box out, inc distributor removal, strip + clean. I using a standard lucus dizzy and pertronix igniter. I static timed the engine it at 12 btc using a test lamp method while on the engine stand.

On attempting to start the engine it wouldn't. Timing light picked up something but was very weak and not the right frequency. On investigating I found that the engine was timed at 12 degree btc, but the rotor arm was half way between the posts on the cap when triggered (~12, 9, 6 , 3 o'clock).

I'll pull the dizzy tomorrow and have a look but I can't figure what I might have cocked up. If I rotate the dizzy to correct the rotor position I'll mess the timing up. Only thing that makes any sense is position of the Pertronix unit being wrong but I believe that only fits one way. Currently in the ~6 o clock position.

Any one got ideas for things to check?

Thanks,

Mark
'73 +2 130/5 RHD, now on the road and very slowly rolling though a "restoration"
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PostPost by: seniorchristo » Sun Jan 01, 2017 3:16 am

Mark
Could you have reinserted the distributor a couple teeth out and timed it on the wrong lobe? I position the engine at TDC when removing the distributor as a reference. :)
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PostPost by: mbell » Sun Jan 01, 2017 3:45 am

seniorchristo wrote:Mark
Could you have reinserted the distributor a couple teeth out and timed it on the wrong lobe? I position the engine at TDC when removing the distributor as a reference. :)


I don't think so, I'd think I'd just have to cancel that out by rotating the dizzy and get right timing.

I have right timing but wrong rotor position. More I think the more I think I must have some how the back plate or pertronix unit incorrectly positioned.

Thanks.
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PostPost by: mbell » Sun Jan 01, 2017 4:52 am

Here is a picture. Engine at 12 degrees btc on cylinder 1. Rotor at ~12.00, lead for cylinder 1 is at ~1.30 on the cap. (Think my leads aren't in the standard positions as per lotus workshop manual, but are correct order.)

So rotor is ~45 degrees advanced to the dizzy cap contact when triggering the electronic ignition.
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PostPost by: Craven » Sun Jan 01, 2017 11:49 am

Hi,
Not sure if it applies to the pertronix ignite but method used by Accuspart etc is, TDC firing stroke on No 1 cylinder rotate disturber as to align rotor are to face No 1 lead in cap. This initial setting should be close enough to start. As I understand things static timing is not possible with these units.
With engine running then adjust with timing light.
FWIW.
Ron
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PostPost by: webbslinger » Sun Jan 01, 2017 5:23 pm

Mark, roll the engine over to tdc and look at where your rotor is now and mark the position. Also mark about where you want it to be to align with the #1 contact. Then pull out the distributor enough to disengage the gears. As you pull it out the rotor will turn some as the gears unmesh. Notice how much it clocks around. Rotate the shaft so the rotor points to the #1 contact plus the amount extra it will clock as the gears remesh when it is reinserted. This will get you pretty close.
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PostPost by: Hawksfield » Sun Jan 01, 2017 6:04 pm

Mark

Make sure you have the correct fitting kit for the dizzy.
You appear to have a 23D, pertronix quote two kits for that type.
John

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PostPost by: el-saturn » Sun Jan 01, 2017 6:24 pm

as nobody complained or asked; all i can say is that my distributor is turned by 90? clockwise and nr 1 is about 120? to the right: the choice of where your cap has cyl. 1 determines the location! - is yours as the picture shows?? cheers sandy
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PostPost by: mbell » Sun Jan 01, 2017 10:44 pm

Sorted it, car now running again :-).

It was a user error, I'd timed it for when the earth connection was made by the pertronix unit not when the was broken. A little corrective education on how the ignition works, adjusted the timing static timing. Started it then adjusted the timing south timing light.

Thanks for all the suggestions, next time I'll check my understanding of how things work is right first....
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PostPost by: tedtaylor » Wed Apr 04, 2018 4:03 pm

I realize this is an old thread, but one I found closest to my problem.
I'm resurrecting an old "barn find" Elan Plus2 and found the spark plug wires disconnected AND not labeled 1,2,3,4, so i'm checking everything and find timing mark at 10 degrees, but my rotor is pointing at 6 o'clock!?!?! So before I take everything apart, I figure the easiest thing to do is make the wires go to 1,3,4,2 (correct firing order) starting with that 6 o'clock at #1 plug. Of course it won't start, so before I take the distributor out and turn 180 degrees and rewire the cap, I was wondering this stupid or simple question and that is.....will the engine fire and run normally with the rotor in "any" position SO LONG AS THE cap wires go to the correct firing order
OR is it critically important that the distributor be in that 12 o'clock position for plug #1 and the wires set sequentially in the correct firing order???
I just can't understand how the car ran years ago with the dizzy in a different orientation that what the service manual lays out.
I think this is NOT the first twin cam engine I've found in a similar disarray.
TED
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PostPost by: ericbushby » Wed Apr 04, 2018 4:38 pm

Hi Ted,
Thinking about that. The distributor runs at half engine speed, so produces four sparks per revolution.
If you fitted the distributor exactly 90 degrees out then the sparks would occur at the right time but on the wrong cylinder. If you then swapped the HT leads round by 90 degrees to follow the error then the engine would run correctly. The remaining problem may be that the leads are pressed up against the block or it is difficult to get to the spring clips on the cap.
So, yes, I believe you can run the engine with the distributor in several positions.
I suggest that you start from first principles and fit it as the book says, for clarity in the future for yourself and maybe others.
Does that make sense?
Eric in Burnley
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PostPost by: alan.barker » Wed Apr 04, 2018 5:02 pm

Eric,
the dissy runs at half crank speed so 2 sparks for each turn of crank :wink:
You can orientate the dissy as you like as long as the rotor arm lines up with dissy contact n?1 at the correct moment.
Alan
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PostPost by: ericbushby » Wed Apr 04, 2018 5:10 pm

Yes Alan, that is what I was trying to explain but just giving one example. Thanks
Cheers
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PostPost by: alan.barker » Wed Apr 04, 2018 5:43 pm

100% Eric.
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PostPost by: tedtaylor » Wed Apr 04, 2018 5:47 pm

i should clarify, that the distributor is pretty close to being in correct position, however it is the rotor that was positioned incorrectly (6 o'clock), so I guess i'll pull the distributor out far enough to turn the rotor to point more at 12 o'clock #1 plug and rewire the cap to the correct plugs via the firing order.

you said 1/2 speed? all I know is every time the crank turns a complete revolution, the pistons travel twice (once for firing and once for expelling), is that correct?
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