Part Five: Ignition Timing

[tree monkey]

18"325 26 rs off the roll, same chain I had in ct

 

[MustangMike]

I got this over 20 years ago for tuning my 440 engine,

Took me a few seconds to realize you were talking about your car!

 

[MustangMike]

Scott, care to share how much off the key gave you 7 degrees?

 

[tree monkey]

the key is part of the flywheel, I just file a bit and check with a degree wheel.

 

[Canadian farm boy]

From my messing around with advancing ignition timing I've found that for every .010" from the flywheel key equals approximately 2.5*-3* of advance. Ymmv.

 

[MustangMike]

I did some crude measurements with an 044 and guesstimated that .020 was about 5-6 degrees, but I won't pretend I was certain about it.

 

[Redfin]

my findings were interesting. the timing seems to jump around at idle, I took an average of 18 deg and 50 deg above 5000 rpm. this seem way to much to me.
I advanced the timing with the key by 7 deg using a deg wheel, and redid the timing light test. idle 32 deg, over 5000 rpm 64 deg. well ok. so the ign sparks twice per revolution. so stock timing is 9 and 25. my advanced key is 16 and 32.

Any theory why the second set of magnets are reversed S to N?

 

[tree monkey]

according to the tech ay stihl 1 set is for spark, the other is for the carb, said it does not spark twice per revolution. after 2 days of testing I found that not to be true on the 261

 

[Deets066]

according to the tech ay stihl 1 set is for spark, the other is for the carb, said it does not spark twice per revolution. after 2 days of testing I found that not to be true on the 261

The other set of magnets still seems to affect rpm even when running a regular carb

 

[tree monkey]

yes it does. I can't prove what I think is happening without a tack that goes over 15,000 rpm, but I believe that the coil on a 661 starts to retard the timing at around 13,200, and a 261 at around 14,000.

 

[wcorey]

These work pretty well and go to 20k, cheap too...

www.ebay.com/itm/Searon-Backlit-Digital-Resettable-Inductive-Tacho-Hour-Meter-Tachometer-/222508163814?hash=item33ce8522e6:g:gskAAOSwHptY-loU&vxp=mtr

 

[tree monkey]

I meant to say I need a timing light that goes over 15k

 

[MattG]

I meant to say I need a timing light that goes over 15k

Well let us know if you find such a thing. What's the highest you've seen one get up to?

I was thinking the other day about how such a device (high RPM strobing gun) would work. Surely the RF pickup electronics would be sensitive enough (since it is already the case in the kind of leccy tachos that are available). But to get the strobe to illuminate long enough for you to see it, but a short enough pulse for it to remain accurate?

 

[jake wells]

i will put my two bits in regarding ignition on a stihl 041 fb with points and condenser but i know it might be a little off topic. higher revs with nova module over the points set up
the points were worn out and the condenser was open on my 041 but it ran fine before it died.

i replaced the works with a nova module and it worked great and ran better than it even had before and seemed to rev higher i didn't touch the coil or check the timing as i seen no need and it doesn't run hot or miss at wide open throttle and starts faster. spark is also hot and fat at the plug.

but i think i figured out why it revs higher with the nova module than with the old points, i think the points tend to float in higher rpms and it kind of limit rpms??
not really sure about it but do points become less affective as the rpms increase?

does the nova module give a little timing advance or no? i know the throttle response is very nice compared to before.
im sure one of you can give me the details on this.

 

[Terry Syd]

I doubt if it was 'float'. The points open as the ramp moves the points to an open position. As some point, there is a break in connection and the current through the primary coil collapses, which causes the secondary to collapse and send a big 'zap' through the plug. The condenser/capacitor is there just to keep the voltage from arching back across the points. It is easier for the current to flow into the condenser/capacitor than to arch across the points.

The ramp for the points is fairly quick, but the points have an entire rotation of the crank to come back and ride smoothly on the heel of the cam.

Maybe the extra 'zap' you noticed at higher rpms was a result of the capacitor ignition system getting a full charge to hit the coil with. A SCR controlled capacitor discharge system has a lot more zap than any old points system.

 

[Dub11]

I meant to say I need a timing light that goes over 15k

So just an idea but we use this adjustable strobe light thingamajig at work on a web press to check registration

We just kind of dial it in till it hits were we need it. I dont know just an idea.

 

[ferris]

yes it does. I can't prove what I think is happening without a tack that goes over 15,000 rpm, but I believe that the coil on a 661 starts to retard the timing at around 13,200, and a 261 at around 14,000.

Can u get a 261 coil work in a 661?

 

[Deets066]

Can u get a 261 coil work in a 661?

@Redfin, I think tried. I don't think it worked

 

[tree monkey]

the physical shape of the coil is the same, the bolt pattern is different, the legs in the coils will interchange. the primary wire connector would need to be modified.

this should work to get more rpm when using a std carb on a 661

 

[Redfin]

@Redfin, I think tried. I don't think it worked

I didnt try a 261 coil.