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tr6 ignition timing


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#1 ashuici

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Posted 21 July 2010 - 07:09 PM

I need some help about the ignition timing. My car is a 1973 TR6 PI frame number 1.CR.316.L with original Lucas fuel injection and Lucas 41501A distributor. According with the Haynes manual the settings wold be: static 11º BTDC, and at 4.000 rpm 6 to 8 degrees on distributor equivalent to 12 to 16 degrees in crankshaft, so maximal advance would be 23 to 27 (12+11 to 16+11) degrees on the crank. However, the arm located in the distributor is marked 14º, that means 28º in the crank and 39º (28+11) total advance. This last is more or less that I can read using my strobe ligth. Wich is wrong? What is the correct timing using stroboscopic gun? Thank you in advance and sorry for my english. Alfonso. Spain.
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#2 foster461

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Posted 22 July 2010 - 01:02 AM

I need some help about the ignition timing. My car is a 1973 TR6 PI frame number 1.CR.316.L with original Lucas fuel injection and Lucas 41501A distributor. According with the Haynes manual the settings wold be: static 11º BTDC, and at 4.000 rpm 6 to 8 degrees on distributor equivalent to 12 to 16 degrees in crankshaft, so maximal advance would be 23 to 27 (12+11 to 16+11) degrees on the crank. However, the arm located in the distributor is marked 14º, that means 28º in the crank and 39º (28+11) total advance. This last is more or less that I can read using my strobe ligth. Wich is wrong? What is the correct timing using stroboscopic gun? Thank you in advance and sorry for my english. Alfonso. Spain.


Hi Alfonso and welcome to the forum.

When you say that the arm located in the distributor is marked 14 degrees what are you referring to ?. I could be wrong and I'm sure someone will soon correct me if I am but the rotor arm doesnt really play a role in the advance and I have only ever seen them stamped with a 4 or a 6 to designate the 4 or 6 cyl engines or with a simple arrow to indicate the direction of rotation. The base plate rotation governed by the centrifugal weights and springs define the mechanical advance characteristics together with whatever static advance you configured plus any vacuum advance. Total advance of 28 degrees at 4000 rpm doesnt sound way off to me but 39 degrees of advance seems like a lot.. Is that what you are seeing with the strobe at 4k rpm ?

Stan
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#3 Mike Collins

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Posted 22 July 2010 - 09:45 AM

Hi Alfonso,

I believe you are referring to the cam under the contact plate, this is taken from a Lucas distributor document by TDC which I hope is attached.




This is the area of focus for this document. After removing the breaker plate you will
see:
· The cam with a stamped maximum mechanical advance figure
· Two small springs, the primary spring being the smaller, or weaker of the two.

My CP series has a 7 degree cam, not sure what the figure is for CR but it should be published somewhere.

Mike.
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#4 ashuici

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Posted 22 July 2010 - 05:23 PM

Mike, you are rigth, this is the arm wich limit the máximun advance. In my case is stamped 14, so I understand it is the total centrifugal advance in the distributor. This means that the advance in the crankshaft is 28 degrees (just the double). If I set the static advance at 11º, the result will be 28+11=39, more or less the same reading I can see with my strobe ligth. This means to be too much advance for this engine and, in any case is a lot different to the data in the Haynes manual. I have dismantled the distributor and everything is OK, without any wear. I am the second owner, so I´m not sure about the possibility of changes in the past, however, all seems to be original, there is not any vacuum in the distributor but the vernier advance adjustement is present working OK. In my search trough internet I only have found a lot of confussion about this theme.

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#5 poolboy

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Posted 22 July 2010 - 06:35 PM

Once an engine has gotten as old as most of ours, I just don't trust the timing marks on the damper to reflect the true ignition timing. The timing chain has stetched, the chain sprockets have worn along with the distributor drive gear set. And even the rubber bond in the damper can give.
Whereas the manifold vacuum will indicate the efficiency of combustion.
This seems to be a better way of finding the sweet spot followed by a few test drives.
http://automotivemil...arage/v2n8.html
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#6 ashuici

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Posted 23 July 2010 - 12:34 PM

Once an engine has gotten as old as most of ours, I just don't trust the timing marks on the damper to reflect the true ignition timing. The timing chain has stetched, the chain sprockets have worn along with the distributor drive gear set. And even the rubber bond in the damper can give.
Whereas the manifold vacuum will indicate the efficiency of combustion.
This seems to be a better way of finding the sweet spot followed by a few test drives.
http://automotivemil...arage/v2n8.html


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#7 ashuici

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Posted 23 July 2010 - 12:50 PM

Poolboy, thank you for your information, in any case this procedure don´t resolve the advance curve problem, also this is for carburetors models, mine is the Lucas injection one. I think would be better stablish the original settings as a start point and after this, make the adecuate corrections according with the age, wear and other factors, like fuel, tuning, etc. This is the reason I´m very interested in knowing the static advance setting (I suppose 11º), and the differents advance readings I have to obtain at 1000, 2000, 3000, 4000 rpm with the srobe gun, at last, the exact advance curve for this model.
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#8 poolboy

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Posted 23 July 2010 - 03:32 PM

If you have vacuum for a brake servo, you can use the Vacuum Gauge.
Using a strobe assumes that the timing marks are still accurate.
I can understand your wanting to know how much the timing advances at the speeds you indicated, but there is no way for you to make adjustments at those intervals. All that is accomplished with centrifugal advance weights and possibly a Vacuum advane, if so equiped, while the engine is running and changing speed.
Once the weights and the spring tension on the weights are set, it's out of your control as far as making continuous adjustments.
Your best bet is to have the distributor "recurved" according to your engine modifications and driving habits, then set the initial timing with a Vacuum gauge with the engine running at idle speed.

Edited by poolboy, 23 July 2010 - 08:06 PM.

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#9 poolboy

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Posted 26 July 2010 - 03:10 AM

You may find this interesting:
http://www.teglerize...lucastuning.pdf
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#10 ashuici

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Posted 06 August 2010 - 05:58 PM

Thanks to everybody, but, the only think I want to know is the correct and original advance curve for this model (1973 Triumph TR6 PI) = grades of advance at 1000, 2000, 3000, 4000, 5000 RPM.
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#11 Tom Fremont

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Posted 06 August 2010 - 07:37 PM

Alphonso,

The Bentley Manual doesn't list your distributor number nor any other for the later P.I. engines. For the early P.I. engines they are 7 degree type, allowing maximum of 14-16 degrees of [ distributor ] advance.

Other models for carbureted cars have 10 or 13 degree weights.

In my experience ( over 100,000 miles in carbureted U.S. spec cars ) + 88,000 miles in 150+ BHP cars on Webers the tendency for the higher advance distributors is to give too much advance, particularly with vacuum assist.

You may not have the original distributor for the engine - others on this forum should know the right spec however. If I can suggest, why not back off the static setting so as to keep the maximum advance under 30 degrees and see how you like it? Your idle quality will actually improve and excess advance is unlikely.

I have found these engines will run well with less than optimum advance curves. For an optimum curve you can have a UK specialist rebuild a distributor to your requirements.
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#12 ashuici

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Posted 09 August 2010 - 11:13 AM

Tom, I will try with 30 degrees of total advance. I´ll tell you something...
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#13 OldBob

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Posted 09 August 2010 - 10:35 PM

Alphonso,

maybe the attached file is of use: it lists your dizzy number as the same unit as fitted to a TR250. I think the CR car with PI has a Lucas 41542 with 12 degrees max advance (or 24 when doubled). As to your request for the advance settings at rev intervals of 1000, the weight is fully out by 4000 so thats the limit of advance, anything faster is the setting same as 4000.
If the advance springs are worn, the weight could be fully out at much lower revs which will advance the ignition too early - maybe get a new spring set or better still get it checked by a dizzy specialist. You need to know which camshaft is fitted to do this properly, the CR & CP is different hence the different ignition timing settings - some manuals I've seen only show the CP car setting.
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#14 Phoenix-1

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Posted 12 April 2012 - 01:01 PM

ASHUICI, (Alphonso),
Pi Cr1 -2845 used 41501,- according to Rimmer Bros UK. But this is aslo mentioned as for TR250!! (carbs) OLDBOB is also correct on that,but,-

Various numbers are generic to the series engines, if 'A' or 'B' means either carb or Pi, I do not know. (It can also mean with or without a vac'.) But the degrees on the cam plate should be low for Pi.

The other dissys are 41542,- yes this is,- from Cr 2846, and 41219 ,- is upto CR1 !! CR is 1973 -75. 125 bhp camshaft, 18/58-58/18

Hope this helps. Nick,UK.
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#15 Rien

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Posted 12 April 2012 - 06:14 PM

Hello Alphonso,

The OE BL Handbook with partnumber 545078 2nd edition says 4.5 dec BTDC. And yes you have the correct distributor with 14 dec max. I do not have the curve for this, sorry

Good luck,
Rien
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#16 andymoltu

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Posted 17 April 2012 - 03:10 PM

I'd go for a maximum advance of 30-32 degrees at say 4000rpm.
If it pinks it may well be that the springs have gone a little slack and allowing it to advince too early - in which case retard a little until it stops pinking or get the dizzy rebuilt.
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#17 Rien

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Posted 19 April 2012 - 09:19 AM

Good idee to rebuild the dizzy when worn but how if you don't have the correct advance curve!
Do anyone have them for a CR with the 41501A ?
My advice? thake a 123Ignition, then you have all new and many advantage more!

Rien
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#18 stuart

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Posted 19 April 2012 - 10:51 AM

Good idee to rebuild the dizzy when worn but how if you don't have the correct advance curve!
Do anyone have them for a CR with the 41501A ?
My advice? thake a 123Ignition, then you have all new and many advantage more!

Rien

Talk to Martin http://www.distributordoctor.com/ he will give you chapter and verse on them.
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#19 ntc

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Posted 19 April 2012 - 11:49 AM

Buy a good quality timing light with advance dial in and it will tell you all you need to know.simples :lol:
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Regards
Neil

#20 Rien

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Posted 19 April 2012 - 12:27 PM

No Neil sorry but that tell you the actual curve with probably tired springs!

Rien
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