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pace
06-16-2005, 05:59 PM
I am having difficulty timint the TR. The instructions state that you should turn the distributor counterclockwise until the light comes on. I have to turn mine clockwise to get the light to come on. I have the timing hole 3/8" left of the pointer (as you set in the car). When I set it like this I get a ping and some disaling (sp) when I shut if off plus it heats up. Same thing when set right on the hole. When timing, I have the #1 piston on compression stroke and the rotor pointing in the vicinity of #1 plug. Am I doing something wrong or is this dist shot? HELP!

Geo Hahn
06-16-2005, 06:20 PM
The book works fine for my TR3A but for my TR4 (same engine as yours) I get ping and dieseling with the stock set-up... even with premium gas (91 octane).

I set it where it runs best.

I do not use a test light and do not have the manual handy but wouldn't the light going OUT indicate the moment the points open?

Instead of a light I prefer an audible continuity tester and turn the engine until the beep stops. Handy because you can keep your eye on the timing mark. I tend to use engine (forward) movement to see where the mark is then adjust the dizzy a bit using the vernier for final tweaking.

Adrio
06-18-2005, 10:29 AM
I have had good luck with this static timing method. If you are getting your light to turn on by turning your dizzy the wrong way you are setting the timing wrong. The light turns on when the point open (this is the point in time when the magnetic field in your coil collapses and generates the high voltage to fire the plug). Remember the points will change from "open" to "close" twice as it were per cylinder. So if you are turning your dizzy the wrong way your timing is set off by one dwell open time period as you have set the wrong side of the open period to the TDC. Hord to type this out but I hope you see what I am saying.

If you follow the instructions to a "Tee" you will have perfect timing. Do you have the adjuster on your dizzy? I assume so.

Geo Hahn
06-18-2005, 12:32 PM
[ QUOTE ]
...The light turns on when the point open...

[/ QUOTE ]

I have not used a light so maybe you can 'splain it to me.

If I were to use a light I think I would connect one lead to a hot connection (e.g. the battery) and the other to the white/black wire disconnected from the CB or distributor side of the coil. This wire is grounded when the points are closed... thus the light would be on. Turning the dizzy (or the engine) until the points open would make the light go OUT.

Is there another way to connect the light that makes it come ON when the points open?

BTW -- when setting static timing by first positioning the timing mark then turning the dizzy I think you want to get the timing mark in place by turning the engine/pushing the car forward only... if you miss it go around again. If you overshoot the mark and then back up the car or engine to get is positioned I think any slack in the timing chain, dizzy drive gear, etc. may give you an innaccurate result.

Dave Russell
06-18-2005, 05:00 PM
[ QUOTE ]
[ QUOTE ]
...The light turns on when the point open...

[/ QUOTE ]
Is there another way to connect the light that makes it come ON when the points open?


[/ QUOTE ]
I guess if you connected the light between ground & the coil/points junction the light would come on when the points open.
D

Adrio
06-18-2005, 11:06 PM
I guess I should explain my statement "The light turns on when the point open" This is taken right out of the manual which states "to determine exactly when the contact breaker points open can be ascertained most accurately by connecting a 12 volt bulb in parallel with the contact breaker points (one lead to earth and the other from the distributor low tention terminal)."

In this configuration when the points are closed there is zero volts between the points (of course sonce they are closed) but when the points are open then you get most of the voltage across the points and the lights turns on (in fact you have a voltage divider at this point with the bulb and the coil forming the resistor stack, but for this purpose the resistance ratio is so high that most of the voltage is across the bulb).

one day I intend to collect up as much of the specifications as I can on the distributor springs and the rest of the timing circuit. From this and the size of the pulley, I want to come up with a dynamic timing method. When I do that I will post the results here so that we can use a stobe light to time the engine. For as far as I have found there is no dynamic timing specification available for the TR2/3/4 engine. If someone has that info already I would love to hear it.

Adrio

Dave Russell
06-19-2005, 01:00 AM
[ QUOTE ]
one day I intend to collect up as much of the specifications as I can on the distributor springs and the rest of the timing circuit. From this and the size of the pulley, I want to come up with a dynamic timing method. When I do that I will post the results here so that we can use a stobe light to time the engine. For as far as I have found there is no dynamic timing specification available for the TR2/3/4 engine. If someone has that info already I would love to hear it. Adrio

[/ QUOTE ]

It shouldn't be too hard to do. All TR2,3,4 are speced at 4 degrees static or initial.

From Georges post on "Lucas Distributors"
https://www.telusplanet.net/~chichm/tech/lucas.pdf

The specs for the various distributors are given in distributor rpm & distributor degrees which are both 1/2 the engine degrees & rpm. Vacuum advance is disconnected.

For examples:
The TR2 #40403A - DM2P4, is speced at 1 degree at 200 rpm, or 2 degrees at 400 rpm engine. 15.5 degrees engine at 1200 rpm engine. 28 degrees engine at 5400 rpm engine.
----------------
Add four degrees engine initial for 6 degrees engine at 400 rpm engine, 19.5 degrees at 1200 rpm, & 32 degrees at 5400 rpm.
==============

The TR3 #40480A - DM2P4, is speced at 1 degree at 200 rpm, or 2 degrees at 400 rpm engine. 19 degrees engine at 1500 rpm engine. 28 degrees engine at 5400 rpm engine.
-----------------
Add four degrees engine initial for 6 degrees engine at 400 rpm engine, 23 degrees at 1500 rpm, & 32 degrees at 5400 rpm.
==============

The TR4 #40698 - DM2P4, is speced at 1.5 degree at 350 rpm, or 3 degrees at 700 rpm engine. 19 degrees engine at 1500 rpm engine. 28 degrees engine at 5400 rpm engine.
-----------------
Add four degrees engine initial for 7 degrees engine at 700 rpm engine, 23 degrees at 1500 rpm, & 32 degrees at 5400 rpm.
================

Note that in the following, a pulley diameter of 7" is assumed. You will need to use your actual pulley diameter. Measure from the TDC mark in all cases.

To mark the pulley, measure the diameter, eg. for a 7" pulley, find the circumference = diameter times 3.14 = 21.98 inches. Divide the circumference by 360 degrees or 21.98" divided by 360 degrees = .061" per degree.

For the TR4 example of 3 degrees at 700 rpm plus 4 degrees initial, 7 degrees times .061" = .427" to the first mark.

For 19 degrees at 1500 rpm plus 4 degrees initial, 23 degrees times .061" = 1.403" to the second mark.

For 28 degrees at 5400 rpm plus 4 degrees initial, .061 times 32 degrees = 1.95" to the third mark.

All marks are from TDC.

As others have said, in the real world, you may have to adjust timing to suit the altitude, type of fuel, engine tune, & driving conditions. It probably would not be good to go over 36 degrees maximum timing.
D

Adrio
06-19-2005, 10:07 AM
Thank you Dave for getting me all that information. Saves me some work. That is exactly what I was going to do.

KVH
07-10-2005, 08:01 PM
Are you sure that's right? The table doesn't show the dwell angles increasing proportionately. They appear to increase along a curve. And the angle for 2700 is only 14. It doesn't appear any simple math works, and it's unclear whether anything other than static timing and point gaps area recommended on the earlier TRs. Just wondering.

Dave Russell
07-11-2005, 02:05 AM
Pretty sure. To start with, the dwell angle does not change. Dwell angle is the number of degrees that the points stay closed. The ignition timing is what changes. Remember that distributor advance specs are usually given in distributor degrees & distributor rpm, which would be twice the advance & rpm in crankshaft degrees & crankshaft rpm. The distributor & cam run at 1/2 engine speed.

The centrifugal advance "curve" is actually composed of two straight sections. The initial advance is controlled by only one of the two advance weight control springs. The other spring is slack at low rpm. This gives a fairly large amount of advance for a given rpm increase from low idle to somewhere around the curve change point of 2500 to 3000 engine rpm. Above this rpm, the second advance spring comes into action & reduces the rate of advance increase with further rpm increases. The centrifugal advance weight stops limit the maximum advance to 28 degrees.

To recap: the angle of 14 degrees at 2700 rpm is in distributor degrees & rpm, which would be 28 degrees at 5400 rpm for the crankshaft.
D

KVH
07-11-2005, 05:04 AM
OK, just a few more questions about "dwell." For a 25D Lucas on a 4A, the table says 1200 RPMs would be 10 degress, and 600 RPMs would be 6 degrees. It's apparently not directly proportional.

Does that mean 1200 RPMs of the crankshaft would be 10 degrees on the Dwell Meter, or is 1200 RPMs referring to the distributor?

Does a Dwell Meter, in fact, register crankshaft or distributor RPMs?

Mine has a scale for RPM's, but I have no idea which it measures.

Let's assume I use the 600 RPM figure and check for 6 degrees. Are you saying that the 4 degree BTDC spec is irrelevant unless we're measuring crankshaft degrees? And in that event you would add 4 degrees--such as 1200 crankshaft RPMs (600 distributor RPMs) equating to 10 (6 plus 4) degress on the crank hub?

Finally, if a Dwell Meter is helpful at all on these cars, why wouldn't the manual say so? Is it presumed that static timing and a feeler gauge for the points is simply the best way to go?

thx

Bill
07-11-2005, 09:29 AM
Try this. Go to Wal-mart buy a $10 timing light and some lead substitute. (CD2 comes in a 32 oz jug for about $6 and seams to work fine)
Set your points correctly with a feeler gauge and put the cap on and resist any further impulse to play with them.
Set the adjuster on the dizzy to about 3/4 the way to full advance then time the car with the timing light. Take it out on the road put it in high gear at about 2000 rpm and push the gas to the floor. It will clatter. Retard the the timing with the adjuster about 1-2 clicks and repeat untill you can live with it reminding yourself that you would not normally run 2000 rpm in top gear and expect to accelerate.
Once you get it right don't touch for about a year. Remember that most of these distributers have 40 years of wear on them so timing is never going to be perfect.
I have owned British cars for 34 years now and I remember a piece of advice given to me by a British mechinic. "When working on a British car don't let your quest for perfection get in the way of doing a good job, if you do you will never enjoy the car."

Adrio
07-11-2005, 11:05 AM
[ QUOTE ]

OK, just a few more questions about "dwell."
Does a Dwell Meter, in fact, register crankshaft or distributor RPMs?
Mine has a scale for RPM's, but I have no idea which it measures.


[/ QUOTE ]

It appears you folk are talking about two different things. The meters measure BOTH dwell and RPM. Some folks call them "dwell" meters but you have to remember they can measure both.

In to your question. When measuring RPM it is measuring engine RPM and NOT distributor RPM. All it is doing is counting the number of times the coil fires in one minute and then the multiple scale effectively divides by the number of cylinders (that is why the 4 cyl. and 8 cyl. are the same scale but you multiply by two).

Dave is correct when he says the dwell is independent of RPM (except for a bit or inertia vs. spring tention on the points). The dwell is set by the point gap and the shape of the distributor cam (both of which are fixed in realtion to RPM).

I thing the dwell meter (when used to measure dwell) was just a convienient and more accurate way of measuring point gap. Our TR3 and TR4 cars never had a dwell published so we are left with using point gap as the only way to set the dwell. This may sound like a cicular reference but in fact point gap and dwell are two ways of measuring the same thing.

Keoke
07-11-2005, 12:34 PM
Adrio. You are correct, point gap is measured with a feeler guage while the corrosponding time interval is measured with a dwell meter. However, if have your engine set up correctly you can use the dwell meter to empirically establish the dwell setting achived using the feeler guage.---Fwiw---Keoke

Adrio
07-11-2005, 01:57 PM
Koeke, That is a good idea. I just did a full tune on the TR3, so I may head out there tonight and take the reading.

Dave Russell
07-11-2005, 04:27 PM
[ QUOTE ]

Let's assume I use the 600 RPM figure and check for 6 degrees. Are you saying that the 4 degree BTDC spec is irrelevant unless we're measuring crankshaft degrees? And in that event you would add 4 degrees--such as 1200 crankshaft RPMs (600 distributor RPMs) equating to 10 (6 plus 4) degress on the crank hub?
thx

[/ QUOTE ]
It depends on whether the six degrees was a distributor spec or an engine timing spec. See if the attached graph helps. It is for a TR3 but yours would be similar. Note that when viewing the timing with a strobe, the initial advance of 4 degrees is added to twice the distributor spec degrees & the engine rpm is double that of the distributor spec rpm.
D