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TR2/3/3A Timing with Electronic Ignition

frankfast

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I recently install a Flamethrower distributor with electronic ignition. I can time it statically with a light at TDC but since there are no other marks on the pulley other than TDC advancing the timing seems like guesswork. Has anyone marked their pulley and used a timing light or is this just a trial and error exercise?
 

Geo Hahn

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Many strobe timing lights have an advance dial on them -- you set the desired advance and when the ignition is there the TDC timing mark on the engine is at the pointer.

These are especially useful for checking advance at high RPM (when centrifugal advance is 'all in').

Alternately you can do some 6th grade arithmetic and figure out where the static timing should be relative to the TDC mark. I seem to recall that 5° BTDC was about ¼" on the pulley.
 

JFS

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I use a timing light that has dial that you turn to match the pulley mark with the pointer. The dial shows the degrees as you turn it to match the marks. You determine what advance you want at what RPM and set the distributor accordingly. I run a Mallory dual point with mechanical advance only and am basically interested in setting the total advance at 3500 RPM.
 
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frankfast

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"Alternately you can do some 6th grade arithmetic and figure out where the static timing should be relative to the TDC mark. I seem to recall that 5° BTDC was about ¼" on the pulley."

That's a good start since my timing light is from the sixties.
 

TR3driver

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One thing to watch out for: The TR2-4 have a timing curve that starts at a very low rpm. The book allows as much as 2 degrees advance even at 400 rpm! So if your idle is a bit high, and you set to 4 BTDC as the book says, you'll wind up with retarded timing.
 

6TTR3A

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I went with a Pertronix, with an original Lucas 3 ohm coil in a Lucas DM2 distributor. AT 3000 RPM advance is
"all out" at 31° BTDC. I did the math, marked 31° in the pulley, set the distributor using an old-fastened timing light.
Car runs great! I noticed at 800RPM (my comfortable idle) the light shows about 10° advance. That seems to correlate with what Randall says.
Frank
P.S. I was a little nervous running at 3000 RPM at no load, but it only took about 5 seconds to get the distributor set.
 
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frankfast

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"I did the math, marked 31° in the pulley"

If 5 degrees is about 1/4" on the pulley, does that mean that 30 degrees is about 1 1/2"?
 

Geo Hahn

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That ¼" was a guess. To calculate 31° (or whatever you want for total advance) measure the diameter of the pulley, multiply by 3.14, divide by 360 and multiply by 31.

I will then tell you what card you selected.
 

TR3driver

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According to my notes, the pulley is 5.50" in diameter, which means 31° is about 1.488" measured along the edge of the pulley (the formula Geo gave above).
Or, if you want to measure in a straight line, the formula becomes diameter times sin(angle/2), which is about 1.470"

YMMV
 
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frankfast

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3.14 = pi I haven't had to use that since high school geometry. Seems like the original guess of 1 1/2" was pretty close. Anyone confirm that full advance is 31 degrees at 3000rpm? Thanks everybody for all the help.
 

Geo Hahn

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There is a 5-digit number on the body of the distributor... possibly begins with a '40'. That will tell you distributor you have.

Here is some data, formatting is crude but hopefully you can follow. 'All-in' advance is in distributor degrees, double that to get crank degrees then add static setting to get total advance.

Pulley: Diameter = 5.5”
Circumference = 17.279”
1° = .048”
4° = .192” (13/64”)
24° = 1.15” (1 5/32”) – Paint mark added to TR4 pulley
32° = 1.54”
34° = 1.63”


Service................RPM/Adv1
Number...Model......(all/in)

40480A DM2P4 2700 15

40698A DM2P4 2700 14

40795A 25D4 1200 10


Triumph TR3 – TR4

Year Vehicle Dist # Vac Unit
Later 1956-61 40480 421953 4-11-7 Hex / spring
1960-62 TR3 40698 A/B 54411480 4-11-7 cap /screw / spring
63-64 TR3-4 86mm 40735 A 54413565 2-6-3 cap /screw / spring
1963- 65 TR4 40795 A 54413565 2-6-3 cap /screw / spring
 
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frankfast

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  • "Tailored advance curve for optimal performance and drivability."

That is the only information Pertronix gives for their Flamethrower distributor.
 

TR3driver

Great Pumpkin - R.I.P
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40480A DM2P4 2700 15

Hmm, I've got 40480 (and the previous 40403) listed as 14 degrees (± 1°) @ 2700. May I ask where you got 15?

BTW, 14@2700 means "all-in" would be total 32 degrees at 5400 crank rpm, ignoring vacuum advance. Specified advance at 3000 crank rpm would be closer to 25-26 degrees.

But it does seem that a stock engine can tolerate more advance on the fuels we have today; depending to some extent on temperature and altitude. I believe the factory numbers were deliberately conservative, to minimize problems under adverse conditions, poor fuel, etc.
 
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frankfast

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After solving a poor connection to the stater motor, the car started right up. It seems someone installed the distributor drive 180 degrees off and then compensated the distributor dogs to match in order to get the rotor pointing toward the No. 1 cylinder. That is the reason the new Pertronix Flamethrower had to be mounted with the rotor pointing away from the No.1 cylinder. I compensated by changing the wires to the plugs. The distributor and new coil work fine and now I can get down to proper timing. Thanks for all the suggestions.
 
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