Ignition timing with Pertronix Ignitor and strobe light

[Bob_Spidell]

Side question: At what RPM is the full advance of 35-36deg achieved?

 

[Lutz Kramer]

Side question: At what RPM is the full advance of 35-36deg achieved?

Bob, since timing is set to 45° BTDC at idle, 35° cannot be achieved at all.

 

[Jim 58 BN6]

Lutz, I think he meant 35 degrees "full advance" *In addition to the idle advance setting. I think you mentioned you measured a total advance of 65 degrees @ 4500RPM, so that would indicate to me an additional advance (due to the distributor's internal advance), of 20 degrees. Jim

*Sorry I screwed this up! Please ignore this part of the post.

 

[Lutz Kramer]

Hi Lutz,
I'm curious how you marked your crank pulley for the 15 and 45 degrees. 15 degrees should be 51/64" (about .8") away from the TDC mark, or 20.24mm.

Here is my timing table and a Foto of the pulley with the timing marks. The pulley has a circumference of 596 mm that equals 23,5".

Timing ​ circumference pulley mm inch ° BTDC 596 23.5 1 2 0.1 5 8 0.3 10 17 0.7 15 25 1.0 20 33 1.3 25 41 1.6 30 50 2.0 35 58 2.3 38 63 2.5

As you can see on the foto I put a yellow measuring tape behind the pulley that proves that the marks have been made in accordance with the table above. Unless the calculations in the table are not wrong the marks should be OK?!

So there is a difference to your calculation that says 15 degrees should be 51/64" (about .8") away from the TDC mark, or 20.24mm while the table shows 1.6" and 25mm. May be your pulley or the one you refer to has a differant circumfererence?

Lutz

 

[Roger]

I think it is quite obvious that it is not igniting at 45deg btdc. It would be very hard to start, and knock like you can't believe.
Drifting off into esoteric wondering about cam timings etc. won't help.

Lutz, please tell us exactly how you measure the timing. You've said it's a strobe light, but is it the kind that flashes a light which you focus on a mark on the pulley or block, or is it the kind which you focus on TDC and it shows the advance/retard itself? Somehow what you write doesn't make sense, sorry.

 

[Roger]

I wrote my last post before I saw yours.

Are you saying you get a strobe flash at 75mm on the circumference?

 

[Lutz Kramer]

Hi Bob,
hi Jim,
I think there is a misunderstanding. The advance I measured at idle was 45° BTDC and 65° at 4500 rpm while the standard timing is supposed to be 15° at idle and about 35° at 4500 rpm. So in both cases the difference beween idle an maximum advance is 20°. I never reached more than 65° even when I took the engine obove 4500 rpm.

 

[Lutz Kramer]

I wrote my last post before I saw yours.

Are you saying you get a strobe flash at 75mm on the circumference?

That's right, Roger! The flash hits the pulley short before the small red marking (38° mark on my Foto)! I use a simple strobe light that cannot be set to a certain advance. But as I mentioned before, I did a static timing before with the Pertronix as well as with my old Mallory dual point distributor. And even then 45° BTDC was the result.

 

[Jim 58 BN6]

Lutz, I think he meant 35 degrees "full advance" in addition to the idle advance setting. I think you mentioned you measured a total advance of 65 degrees @ 4500RPM, so that would indicate to me an additional advance (due to the distributor's internal advance), of 20 degrees. Jim

Sorry, I confused myself. After re-reading my post, I'm sure he meant total advance of 35-36 degrees, including initial setting, indicating distributor internal advance of 20 degrees. Not enough coffee, or yet another senior moment!!

 

[steveg]

In computer troubleshooting the rule was always: something's broken or something's changed. Applies to cars too. The Mallory is what's changed. It requires drilling its shaft to pin the Healey drive gear. I wonder if there's a way for it to function correctly with the strobe timing seemingly in the wrong place on the pulley.
I'd want to go back to basics and make sure the Mallory was properly located on the shaft and check the setup for an Austin Healey.
Is the pulley in the picture a stock later BJ8 pulley?

 

[Bob_Spidell]

Sorry, my question was regarding when does full advance come in on a car that isn't possessed by demons (i.e. 'stock')? I should have been more clear.

 

[Lutz Kramer]

In computer troubleshooting the rule was always: something's broken or something's changed. Applies to cars too. The Mallory is what's changed. It requires drilling its shaft to pin the Healey drive gear. I wonder if there's a way for it to function correctly with the strobe timing seemingly in the wrong place on the pulley.
I'd want to go back to basics and make sure the Mallory was properly located on the shaft and check the setup for an Austin Healey.
Is the pulley in the picture a stock later BJ8 pulley?

Steve, I can't tell you whether the pulley is a stock or not. But when I go to Limora which is here in Germany one of the biggest suppliers of Healey parts they offer a pulley together with a damper as one part that looks like mine and say that its for BJ8s from engine #29K-H10272 on and is especially made for 13mm = 1/2" drive belts.

 

[John Turney]

Table corrected at request of Lutz.

 

[Lutz Kramer]

Are you measuring your timing marks using inches or mm? If you are using inches, please check your math. I get 2.5 inches at 38 degrees. If you are using mm, our math agrees.

I'm measuring on the basis of mm! And you are right, the calculation for inches was not correct due to improper use of Excel! Mea culpa!

I have corected the table. Thanks for the info, John! May be you should eliminate the table from your post above, so that no faulty information is circulating in the forum.

 

[Lutz Kramer]

I just want to to let everybody know that I gonna be on vacation until 24th of October and therefore cannot reply to messages during this time. For the 25th of October I have an apointment wit BOSCH to find out if there is anything wrong with the ignition. Thereafter I will get back to you to let you know if there are any news.

I would like to thank all of you for the efforts and help that I have been received so far.

 

[Lutz Kramer]

Back from from vacation and from Bosch! Here is what they found:

To recap:

1. First of all I found with a strobe light the ignition timing to be set at 45° at idle and 65° at about 4500 rpm.
2. I then replaced the old no resistance igniton wires with new no resistance wires and measured 30° at idle, but still not 15° (may be due to electrical interferences)
3. Next thing I did was to replace #1 sparkplug wire with a resistance wire --> but no difference!

Bosch measured 23.9° BTDC! They use a computer system which a strobe light with advance control is attached to.



So, my strobe light ist about 6° off!

But what about 23.9°? They confirmed, that the enginge is running very well with this timing. When I told them, that the engine has a hot cam, they said that this might be the reason for this kind of advanced setting. A hot cam may sometimes afford an advanced setting up to 10° more than recommended by the factory. It depends on the engine. Since they do not have expreriences anymore with Healey engines, they cannot say that this definitaley applies to the BJ8 engine. But they also confirmed that it is more important to set the ignition at high rpm and therefore in accordance with the AH 3000 workshop manual it should never exceed 38°.
They also said, that the engine with its hot cam might perfom better at high rpm if they would set the timing closer to 15° but it then might run very poor at low rpm.
Since I rather prefer cross country trips at low speeds than to go for races I decided to leave the engine at 24° at idle and about 38° at 4500 rpm.

That's it!

Thank you all for your help and patience!
​

 

[HealeyRick]

Lutz,

So the problem appears to have been in your strobe light, but you said you tried the strobe light of a friend that read the same as yours. What's the difference between the Bosch light and the two that you tried?

 

[Jim 58 BN6]

Lutz,

So the problem appears to have been in your strobe light, but you said you tried the strobe light of a friend that read the same as yours. What's the difference between the Bosch light and the two that you tried?

Rick, my guess is that a professional system is much more carefully shielded from electrical noise.

Lutz, I'm glad you've apparently found out what's really going on. Enjoy! Jim

 

[Lutz Kramer]

Lutz,

So the problem appears to have been in your strobe light, but you said you tried the strobe light of a friend that read the same as yours. What's the difference between the Bosch light and the two that you tried?

Hi Rick, I believe it's the quality of the strobe light, like Jim said. The strobe I tried from a friend of mine was indeed from a different manufacuterer, but may be of the same poor quality. For instance if I unplug my strobe from the wire it continous to flash until I remove it completely out of the engine compartment.

 

[Jim 58 BN6]

For instance if I unplug my strobe from the wire it continous to flash until I remove it completely out of the engine compartment.

That says a LOT about how electrical much noise your engine is making - but I wouldn't worry about it!