Static Ignition Timing Using Strobe

[William2]

This is more of a confirmation issue rather than a question regarding using a strobe for static timing.
Having just had my camshafts out to re-shim the valve clearances I had to redo the timing and removed the distributor and reset as per normal procedure. I have a Powerspark module fitted to the dizzy (same as Accuspark, etc) and the following timing method works well in spite of the fact I have a high torque starter motor spinning the engine so less revs than the standard Lucas one.
With all plugs removed and No. 1 plug fitted to its ht lead, a switch lashed up to operate the starter solenoid and the strobe sensor connected to No. 1 lead. With the strobe pointed at the white timing marks I spin the engine on the starter motor and the timing marks light up very well to show the 10 degree static timing setting required. It also helped having the garage lights switched off.
There has been some debate in the past as to whether this method works or not and I can certainly confirm that on my set up it works very well and it has the added bonus that the ignition timing can be set accurately without having to start the engine.

[Bits]

Hi William,

I am looking at the Powerspark electronic ignition to go into my dizzy. Has the tacho been modified to make it work properly please?

Regards,

Mark.

[nmauduit]

depending on the spark timing accuracy you are after, you may have to consider an eventual lag between the crank pulley mark at 0 and actual TDC (on my S4 there was 4?, but some of it may have been coming from the use of vernier cam sprockets)
---- edit
with a clearer mind and after a cup of coffee, I don't see how the vernier sprockets could impact the timing of the dizzy (only the chain elongation would, my guess is now my cranck pulley was stamped/marked a bit off)

[William2]

Hi Mark,
Luckily I found that the tacho worked fine with the Powerspark module without any mods. Regards, William

[69S4]

depending on the spark timing accuracy you are after, you may have to consider an eventual lag between the crank pulley mark at 0 and actual TDC (on my S4 there was 4?, but some of it may have been coming from the use of vernier cam sprockets)

I wondered about that and checked it on my engine with a dial gauge down the plug hole. The pulley timing mark was spot on and I've subsequently been happy to rely on what the strobe light tells me. As the relationship is between the piston and something (the pulley) bolted to the crank I wouldn't have thought the cams would have a dog in that fight ?

[JonB]

When I did mine I connected a light to the positive side of the coil and rotated the crank by hand. The spark seems to be generated when the light goes off, so I set it to 12 degrees BTDC using the case markings which I?d checked (they were spot on). Some turning the crank back is necessary to reset the sensor. When I started the engine and checked with the strobe light, it was only 2 degrees out.

I have a contactless Hall effect ignition module fitted like yours.

I think this is marginally safer as you aren?t turning the engine using the starter motor and a temporary switch.

[Chrispy]

When I did mine I connected a light to the positive side of the coil and rotated the crank by hand. The spark seems to be generated when the light goes off, so I set it to 12 degrees BTDC using the case markings which I?d checked (they were spot on). Some turning the crank back is necessary to reset the sensor. When I started the engine and checked with the strobe light, it was only 2 degrees out.

I have a contactless Hall effect ignition module fitted like yours.

I think this is marginally safer as you aren?t turning the engine using the starter motor and a temporary switch.

This is the way I set initial timing as well and it's always been spot on when verifying when running. Doing it with a hot engine is just going to end up with me burning myself

[William2]

Cranking the engine on the starter motor with a temporary switch is perfectly safe. Miles Wilkins confirmed to me that with Dellortos the timing is 10 degrees BTDC.

[nmauduit]

depending on the spark timing accuracy you are after, you may have to consider an eventual lag between the crank pulley mark at 0 and actual TDC (on my S4 there was 4?, but some of it may have been coming from the use of vernier cam sprockets)

I wondered about that and checked it on my engine with a dial gauge down the plug hole. The pulley timing mark was spot on and I've subsequently been happy to rely on what the strobe light tells me. As the relationship is between the piston and something (the pulley) bolted to the crank I wouldn't have thought the cams would have a dog in that fight ?

indeed! dunno what came to my mind... corrected the post above

I only use the pulley mark for quick sanity checks (quite rare on my cars), actual spark timing I do with a depth gauge on the top of piston 1 (same amount before and after TDC while rotating the crank CW, then TDC is in the middle).

[RogerFrench]

I'm having difficulty with the idea that spinning an engine with a strobe is performing static timing, which is usually performed with an engine stopped (static) at a specific point and the position of the distributor adjusted.

[JonB]

Cranking the engine on the starter motor with a temporary switch is perfectly safe. Miles Wilkins confirmed to me that with Dellortos the timing is 10 degrees BTDC.

Fair enough, but you can't wind it back to deactivate the Hall effect sensor. By the way, he said the same to me and I set it to 10 degrees but didn't like the way it ran. Put it back to 12. YMMV of course.

[JonB]

I'm having difficulty with the idea that spinning an engine with a strobe is performing static timing, which is usually performed with an engine stopped (static) at a specific point and the position of the distributor adjusted.

It's to do with the advance curve of the distributor. You don't get advance (if it is performing to spec) below 1000RPM so setting the timing to equal the static timing value at idle with a strobe is what most people do I expect.

Then increase RPM and check the advance is kicking in and correct.

[William2]

Exactly the point Jon. Static timing is the same as running the engine to at least 1500rpm which is why you can use the strobe with the starter motor.

[RogerFrench]

Aha, dynamic setting of a static value. My point was the choice of words.
I fully understand what you mean, but static still means stopped.

[William2]

I apologize for my poor use of words and I need to correct myself again, the static timing value doesn't change below 1000rpm not 1500 as I had previously stated.