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Hi

 

Since messing about with the timing the car is running well but occasionally overruns when I switch off after a long run.

 

Does it mean that it needs retarding or advancing?

 

Thanks

 

Camilo

 

EDIT

 

I decided to check the timing in a local garage using their large professional equipment (Bosch) and ended up setting the timing at around 10º

 

I am now thinking that the problem had/has to do with my failure at setting the timing earlier* and left it in such a way that it promoted overheating, especially as it stopped and did not receive the normal air flow that you get while driving in top. My problem now is that I am not sure if I at 10º I advanced or retarded the timing. I assume that I retarded, but overheating is usually due to retarded timing. No?

 

* The car was running well in my recent 500km run. I then decided to have ago at the timing and failed miserably, ending up with setting by sight (placing the timing mark more or less where I thought it should be). The result was that the car still ran well but probably overheated when it shouldn't,

Edited by qim
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Camilo,

 

The timing on my TR3a is set at between 10 and 12 BTDC when idling. - I say between because it varies with the idling speed but at about 800 rpm it is just a shade over 10 BTDC according to the marks that I scribed on the front pulley when I rebuilt the engine. More importantly, if I advance it any further, the engine starts to 'pink', so I guess that is about right.

 

Your engine will be different depending on whether or not the compression ratio has been changed by skimming the head and/or the quality of fuel that you are using.

 

My suggestion would be to advance the timing by small amounts using the vernier if possible, until it 'pinks' and then retard it a bit so that it stops 'pinking'. You will know when it is 'pinking' - it's a high frequency rattling sound when pulling from low revs. Once you have it set in this way, check it with your timing light and make a note of the setting for future reference as you will need it when your points wear and you need to change them.

 

Yes engines overheat when retarded (due to the incomplete fuel burn I think) but in my experience they have to be quite seriously retarded for that to happen.

 

As far as running on is concerned, again my experience is that some old engines do and some don't. It isn't an issue for modern engines with EFI.

 

Rgds Ian

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With a 10 degree cam in the distributor giving 20 degrees mechanical advance setting a 32 degree maximum will result in 12 degrees at tickover. With a compression ratio around 9.5:1 pinking should not be a problem and the engine should tick over nicely around 800rpm.

The mechanical advance should be fully in by 3000rpm.

I normally use one of the premium unleaded fuels.

As for driving in London Roger....????????????

Exeter is the big city in these parts and I don't much like driving there. That's what bikes are for????????????

Edited by Drewmotty
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Easiest first thing to try to cure running-on is colder running plugs.

Heat grade numbering varies with manufacturer:

https://www.boschsparkplugs.net/learning-center/article/225/heat-range-conversion-chart

 

Higher octane fuel can also cure running-on.

 

Peter

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Hi Peter

 

The car was running well, without any problem. I did a 500km run in very hot weather (36º in the shade) and did not lose a drop of radiator water.

The next day I decided to have a go at the timing and made a mess of it. To get the car going I set the timing by placing the mark more or less where I thought it should be, by sight alone (with the help of the strobe light. Unfortunately I could not get the strobe to measure the angle). The car ran well but today after a 50km run (in about 24º) I lost nearly a litre of water and the car ran on when I turned it off.

I think that I left the timing much too retarded, which promoted overheating. Using a local garage's equipment I set the timing at 10º. For that I turned the distributor a bit anticlockwise. If that is the way to advance the timing it means that before it was much below that.

 

I only drove a couple of Km since and don't know where I am now, but I think that I know how to go from here if turning anticlockwise is the way to advance the timing.

Edited by qim
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Hi Peter

 

The car was running well, without any problem. I did a 500km run in very hot weather (36º in the shade) and did not lose a drop of radiator water.

The next day I decided to have a go at the timing and made a mess of it. To get the car going I set the timing by placing the mark more or less where I thought it should be, by sight alone (with the help of the strobe light. Unfortunately I could not get the strobe to measure the angle). The car ran well but today after a 50km run (in about 24º) I lost nearly a litre of water and the car ran on when I turned it off.

I think that I left the timing much too retarded, which promoted overheating. Using a local garage's equipment I set the timing at 10º. For that I turned the distributor a bit anticlockwise. If that is the way to advance the timing it means that before it was much below that.

 

I only drove a couple of Km since and don't know where I am now, but I think that I know how to go from here if turning anticlockwise is the way to advance the timing.

Hi Camilo,

Turning the distributor clockwise ( viewed looking down on it) advances the spark.

Personally I'd use Ian's method , post 2 to get it running right. Timing is not supercritical in road tuned engines.

Peter

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Hi Camilo,

Turning the distributor clockwise ( viewed looking down on it) advances the spark.

Personally I'd use Ian's method , post 2 to get it running right. Timing is not supercritical in road tuned engines.

Peter

 

That destroys my theory!

 

I take it that you mean looking down on it from opposite the engine, right? From the left hand of the car where the distributor is.

 

I turned a bit anti-clockwise. That means I made it even more retarded than it was already, and I expect the overheating and running.on will remain!

 

Could it be that my running.on and overheating were caused by a too advanced timing?

Edited by qim
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Looking down from directly above the distributor - regard the centre HT lead as the center of the clockface. Turnig it clockwise advcances the spark. - makes the spark earlier in relation to the crank. Because the rotor arm turns anti-clockwise.

 

Over advanced engiens make a terrible loud pinking/knocking nosie or wont even start.

Over-retared is far less obvious, but the sparks have to be very late to overheat badly, and the engine will barley run at low rpm and wont take any load. It will pick up as the centrifugal advance comes all in at around 2500-3000rpm

 

Peter

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Camilo, the rotor arm turns in an anti clockwise direction so turning the distributor clockwise moves the cam of the points towards the position where they open. In other words it makes the spark happen sooner in the cycle i.e. Advances the timing.

 

Rgds Ian

 

What Peter said. I just read his post!

Edited by Ian Vincent
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Thank you Ian

 

I will play with the vernier as you suggest.

 

Incidentally: what do you use to measure the angle? A strobe? What type?

I can't measure the angle accurately. When I rebuilt my engine, before I permanently fitted the crankshaft pulley I trial fitted it with the crank at TDC and marked it on the pulley. (I was fitting a narrow belt conversion kit so the pulley was a machined one and not the standard TR pressed steel assembly). I then marked the pulley at 5 degree intervals for 30 degrees advanced and 10 degrees retarded.

 

As a result, when I run the engine I can only see approximately how advanced the timing is because my timing light is not one of the modern ones that allow you to adjust the timing of the flash and hence measure the timing accurately, it is at least 30 years old and simply flashes when number one cylinder sparks.

 

Rgds Ian

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my timing light is not one of the modern ones that allow you to adjust the timing of the flash and hence measure the timing accurately, it is at least 30 years old and simply flashes when number one cylinder sparks.

 

Rgds Ian

Mine too. Nice and simple. Like this, with a simple on-switch and no dial to confuse things. Put the sensor on #1 plug's HT lead and the light flashes the instant the lead goes live. It freezes the view of the crank pulley at that instant.

 

http://www.ebay.co.uk/itm/Ignition-Strobe-Timing-Light-Gasoline-Engie-Inductive-for-Car-Motorcycle-MA1166-/192291379668?hash=item2cc57599d4:g:1Z0AAOSwT-lZpHXE

 

Beware of the fan hitting hand.

 

Peter

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Very confused! (as usual!)

 

I took the car out, and as before it got rather hot and I feel that it is not surging forward as before. The running on when I switch off is probably due to the hot engine.

 

Now, I assume that when I messed up with the timing I left it too retarded whicvh would account for the above. As I wrote before, in a professional machine the timing was left at 10º which would probably need advancing. But today after the run I used the strobe and while when the car was running very well (3 weeks ago) showed 24º, now it came up with 44º!!!

 

So.either the strobe is useless, or the car is way too advanced. Could that account for getting hot?

 

I will try Ian's method tomorrow, but if it is too advanced why does it not pink?

 

Camilo

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Very confused! (as usual!)

 

I took the car out, and as before it got rather hot and I feel that it is not surging forward as before. The running on when I switch off is probably due to the hot engine.

 

Now, I assume that when I messed up with the timing I left it too retarded whicvh would account for the above. As I wrote before, in a professional machine the timing was left at 10º which would probably need advancing. But today after the run I used the strobe and while when the car was running very well (3 weeks ago) showed 24º, now it came up with 44º!!!

 

So.either the strobe is useless, or the car is way too advanced. Could that account for getting hot?

 

I will try Ian's method tomorrow, but if it is too advanced why does it not pink?

 

Camilo

Probably its too retarded - are you confusing 44 ATDC with BTDC ?

Use Ian's method, it eliminates misreading a strobe.

Peter

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Probably its too retarded - are you confusing 44 ATDC with BTDC ?

Use Ian's method, it eliminates misreading a strobe.

Peter

 

44º on the strobe gun (it reads btdc, I think) , while before when it ran very well was 24º. I shouldn't have touched it...

 

OK. Tomorrow, using Ian's method I will use the vernier to advance it, first by some 4º and then go from there. I understand that 1º on the vernier is 10 clicks; so I will advance it 40 clicks.

 

Does that sound reasonable?

Edited by qim
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Hi Ian,

you could 'snopake' the 5' markers. That way you will approximate better.

 

Roger

I did better than snopake Roger, I filled the grooves that I had filed with white enamel so the marks are nice and visible, I also bent the pointer attached to the timing chain cover so it was only a mm away from the pulley to remove as much parallax effect as I could but I can still only estimate the timing. It is slightly more than 10 degrees but whether it is 11 or 12 degrees is anybody's guess.

 

Rgds Ian

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Camilo,

 

I would start from TDC and move forward from there, in which case your 40 clicks is about right. Note when adjusting the vernier there are marks on the distributor indicating A & R. If you run out of 'clicks' on the vernier, you need to move the distributor slightly and reset the vernier.

 

And finally, note that you have two ways of moving the distributor body, one is to slacken the clamping nut and the other is to loosen the two bolts holding the clamping ring to the block and rotate that, (the holes in the clamping ring are slotted).

 

Rgds Ian

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44º on the strobe gun (it reads btdc, I think) , while before when it ran very well was 24º. I shouldn't have touched it...

 

OK. Tomorrow, using Ian's method I will use the vernier to advance it, first by some 4º and then go from there. I understand that 1º on the vernier is 10 clicks; so I will advance it 40 clicks.

 

Does that sound reasonable?

You have to know its reading BTDC. Its highly unlikely its is 44BTDC at tickover as the engine would have pinked really loud upon accleration !

Set the points to just open when the crank pulley is at 10BTDC. The use Ian's pinking method

 

Peter

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Hi Peter

 

Thanks but now I don't understand! From what Ian wrote I assume that I get out of bed and turn the vernier 40 clicks anti-clockwise (advance) and go for a run. If it pinks I retard it a bit, If it does not I advance it more, etc.

 

Now you are talking about setting the points, whci means that ll this vernier business should be done with the engine not running... I don't get it

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