Timing Anomaly

[SpacerM]

Trying to tune up my BJ8- it runs fine but I have never checked the timing. Under the strobe, the timing mark looks about 1” BTDC and holds steady. As soon as I dial in advance to the strobe gun, the timing mark jumps wildly (at least 3 inches, including to the other side of the mark). 600 RPM. Vacuum advance disconnected. Positive ground. Petronix Ignitor in an otherwise standard dizzy. Original style Lucas side entry cap. Can’t tell if my wires are solid core or not, but they are not original.

Tried with induction clip at both ends of the #1 wire (facing towards plug), gun hooked direct to the Healey battery, to an external battery and to the Healey generator with the same result. Tried this with two induction guns, one digital and one dialback-same result.

I don’t think it’s the mechanical advance, as the mark holds steady with 0 degrees advance in the gun. I’m questioning the wires, which are clearly old but I don’t want to be chasing my tail replacing the wrong parts. Any ideas on what may be causing this? Would buying a top entry cap and carbon wires be a smart next step? Thanks for any insights.

 

[AH100M]

It's not clear to me how you're using the timing light.

At idle, adjust the advance knob on the timing light until the TDC mark on the pulley aligns with the reference mark on the engine. (Easier to see if they're both painted white). Read the idle advance setting off of the dial on the gun. Then increase the idle to the RPM at which you want to measure the advance. Again, adjust the advance knob on the gun to re-align the TDC mark with the pointer. Read the advance off of the dial of the gun.

Works for my positive ground 100 using an external battery.

 

[SpacerM]

Thanks, Bill. First, I'm using the timing light as a good old fashioned, no advance feature light with the advance feature set to 0 degrees. This is when the mark is about 1" BTDC. Now dial in any advance (10 degrees, 35 degrees, doesn't matter) on the timing light and the mark starts to jump- no change in RPM necessary- jumps as soon as I move the dial and I can never align the mark with the pointer. This has me thinking the gun is getting confused by the spark coming down the #1 plug wire and is strobing at the wrong time, but before I start replacing parts that are otherwise working (as the car runs smoothly) I'm wondering if anyone has any other ideas or thinks I am chasing the wrong "solution."

 

[AH100M]

The mark IS supposed to jump! Try what I said - increase your RPM to 2000 or so and re-zero the timing marks using the knob on the gun. Does that work or are you saying any rotation of the advance knob on the gun causes an unstable (i.e., the marks jump around) flash? The pulses going down the plug cable are what is triggering the light so they can't cause the light to flash at the "wrong" time unless something is wrong with the advance circuitry in the gun.

 

[SpacerM]

Bill, appreciate you helping with this. I set the RPM to 2000 using the fast idle screws and confirmed it with an external tach. Zeroed out the timing light and the mark appears about 2" BTDC. When I now slowly rotate the advance dial on the gun, I get two marks, about an eighth of an inch apart, alternating quickly back and forth. The mid-point between these marks remains about 2" BTDC and no matter how much advance I dial into the gun, the marks remain several inches before the pointer- the gap between them widens as I increase the advance on the dial, but they never get "up" to the area of the pointer, so I never get close to being able to "put the mark on the pointer"

I know blaming the plug wires is a long shot, but I'm operating under the assumption the strobe is not in sync with the spark on #1, and I don't have any other ideas.

 

[Legal Bill]

It is always a good idea to be sure you have good wires. Is there any play in the distributor shaft?

 

[SpacerM]

It is always a good idea to be sure you have good wires. Is there any play in the distributor shaft?

Thanks, Bill. Shaft seems firm in the brushing and with the timing gun on zero the mark holds steady, so I believe the dizzy and the advance springs are in good order- also, the car runs evenly.

Doing some searches here and Bosch wires seem well recommended (and black!) but I can't seem to find them locally so am trying to figure out a part number that will fit the BJ8 so I can order online.

Will report back back once I try new carbon wires.

 

[GregW]

If you have the original cap that screws the plug wires in, you don't want to use carbon wires.

You don't mention what type of Pertronix you are using. If you have a Second Strike unit, that may be your issue. My multi spark ignition completely confuses all but the most basic timing lights.

 

[AH100M]

I think Greg may have nailed it. The timing light is not compatible with the ignition system in your car.

 

[SpacerM]

Thanks, guys. I think I need to try new wires and fiddle some more. Right now the car has an Ignitor (presumably the "original"- the sticker jut says Ignitor) in the distributor with a replacement side entry Lucas cap. I have a top entry cap in the spares pile from a spare dizzy I bought online and intend to rebuild one of these days, so once I figure out which Bosch set will fit the BJ8, I'll swap those in and see where that leads me.

 

[Patrick67BJ8]

Thanks, guys. I think I need to try new wires and fiddle some more. Right now the car has an Ignitor (presumably the "original"- the sticker jut says Ignitor) in the distributor with a replacement side entry Lucas cap. I have a top entry cap in the spares pile from a spare dizzy I bought online and intend to rebuild one of these days, so once I figure out which Bosch set will fit the BJ8, I'll swap those in and see where that leads me.

I have a Pertronix in my BJ8 Dizzy and I purchased a top loader cap and wires from Jeff at Advanced Distributors. He had the Bosch wires ceaper than I could find them anywhere else. He may even have a few ideas about your timing issue.

 

[RAC68]

Have you ever thought the issue is in your adjustable timing light and not your ignition system? If you use yours timing light as infrequent as I do and the unit is not new as well, it is not hard to expect that corrosion may have developed in the adjuster and other parts of the unit. This corrosion could unsettle the operation of the readings from the ignition and cause the fluctuations experienced. I experienced something similar on my Sears Timing Light and corrected the issue with a few shots of tuner cleaner. The unit seems to work perfectly now, however, without a way of validating the readings (only one Timing Light), I can’t be certain.

Just a thought,
Ray (64BJ8P1)

 

[SpacerM]

Have you ever thought the issue is in your adjustable timing light

Thanks, Ray. Admittedly I'm a neophyte with timing lights, but I have tried this with two brand-new units, one cheapo dial-back, and the other a reputable fully digital model with the same results. Will try new wires, and if that doesn't work I'll pull the Petronix and replace with points to see if I can narrow down the issue.

 

[why]

Just got my first smart phone and laptop (need a "hotspot" for cabin in mtns--no highspeed) so you will understand when I say never heard of this type of timing light. Mine is based upon watching strobe stop marks on pully against fixed point on engine that matches with TDC. How do you change timing on engine by adjusting light? If someone has spare time would be interested in answer--maybe it compensates blinking so many degrees based upon signal from plug 1 so that when timing in engine 6deg BTDC light due to internal compensation will blink at TDC?
Thanks, Jay

 

[JAV]

Just got my first smart phone and laptop (need a "hotspot" for cabin in mtns--no highspeed) so you will understand when I say never heard of this type of timing light. Mine is based upon watching strobe stop marks on pully against fixed point on engine that matches with TDC. How do you change timing on engine by adjusting light? If someone has spare time would be interested in answer--maybe it compensates blinking so many degrees based upon signal from plug 1 so that when timing in engine 6deg BTDC light due to internal compensation will blink at TDC?
Thanks, Jay

they come with a chip that translates the time between sparks into degrees, allowing the dial to delay the light by the desired degrees.

 

[DerekJ]

How do you change timing on engine by adjusting light? If someone has spare time would be interested in answer--

You don't. All it does is allow you to know the advance at whatever revs you are measuring.

Do it the old fashioned way. Progressively advance your distributor until you get pinking then retard a degree. That way you are not depending on arbitrary numbers like 33% or 35%, which may not be correct anyway as these lights are not precise.

 

[SpacerM]

Update- Turns out it was an interaction of the old copper wires and the Petronix. Sourcing plug wires to fit the top entry cap from Moss locally turns out to be no easy task as all the sets are coded to a particular car, and don’t provide length or fitting information. I recalled that that the TR6 came with a top entry cap stock for its Lucas 22D dizzy, and then guessed that as it has a straight 6 with a centrally mounted distributor, it was likely to fit. My local shop showed Bosch 09287 as the correct set for the TR6, and it turned out was a perfect fit.

After the switch to the new cap and wires, the Innova and Craftsman digital lights were now readable, but still jumped around a touch every few seconds or so, while the cheapie dialback was much steadier. Turns out my timing was set at 12 degrees at 600 RPM, and 33 degrees at 4000 RPM, so it seems this week’s exercise was less about tuning up the Healey and more about educating the owner. Thanks again to all who helped me through this one.