Adjustable Timing Light - How does it work? [Archive] - Chevelle Tech

: Adjustable Timing Light - How does it work?

Nov 21st, 01, 4:38 PM
Educate me here. I've never used an adjustable timing light, only the old fashioned point and turn the distributor type. In three or four easy sentences, what's the theory and specifically, how is one used? I'm sure some brands are better than others...anything to look for specifically?

Dale McIntosh
TC Gold #92/ACES #1709
67SS & 67 Elky

Nov 21st, 01, 6:35 PM
Although I don't own one and have never used one, these devices are very useful for discovering the amount of timing your engine has at any given rpm. They way I understand it, you can set your rpm anywhere you wish and "dial back" the timing mark to zero using the knob on the timing light (by "dial back", I mean watching the timing mark on balancer while your engine is running and adjusting the knob to bring back the timing mark to zero degrees). You would then read the amount of timing marked off in degrees around the outside of the knob and that is your total timing at this rpm. The only thing I am not sure of is if you need to add your initial timing to the timing found as explained earlier. Maybe someone else can clear this up for both of us. I am no help as far as what brand to buy, but I will watch other replies to your post and see what suggestions other guys may make.... as I would like to own one of these useful tools myself!
Hope all this was of some use to you.... If I got this all wrong I appologize in "advance" !!!! HA! HA!
Take Care!

Nov 22nd, 01, 7:39 AM
The adjustable timing lights are good for getting a "range" on the dynamic timing of your engine. I prefer putting a timing tape on the balancer and using a conventional rather than an adjustable timing light. I think the timing tape method is more accurate.

Nov 22nd, 01, 8:46 AM
I already have a fully degreed balancer from Fluidamper and with a tach hooked up I can see my total advance with the standard light I have now.

So the only advantage is that without a fully degreed balancer you can set the RPM, dial the balancer back to zero and read the total advance at that RPM?

Dale McIntosh
TC Gold #92/ACES #1709
67SS & 67 Elky

Nov 22nd, 01, 12:18 PM
An adjustable timing light comes in handy in 2 cases. One is if the timing tab is hard to see (under the water pump for instance) and the other is when the tab is physically too short with respect of the total timing (vacuum and/or mechanical) you would want to measure.

A timing light uses an electronic triggering system to flash a neon (or xenon) tube when the pickup senses a plug is fired. The adjustable version simply allows you to delay the flash the appropriate amount of time by turning the knob.

You can check the adjustment feature by setting the knob to zero and noting the flash position of plug nr 1 and then picking up the signal from the next plug which is known to fire 45 (V8 engine) degrees earlier. By turning the knob you bring the flash back to the same place and the dial should also indicate 45 degrees.


[This message has been edited by rusty66 (edited 11-22-2001).]

Nov 23rd, 01, 1:46 PM
Dale, if you have an MSD or Crane ignition box, these lights do not work. I think the multiple spark boxes "confuse" these lights. I found this out the hard way. I had to return the adjustable and get a standard unit to time my 66.

Tom Wood
Gold Member #66
502 Powered '66 SS

Some pictures of my '66 under construction;
My 66 Pictures (

Dec 1st, 01, 7:22 PM
Very true. MSD on their website recommends against dial-back timing lights for use with an MSD box.

Dec 1st, 01, 8:12 PM
Thanks guys. I do have a MSD unit on my SS but it's also computer controlled via the Accel/DFI injection so a timing light is only used to set initial anyway. Guess I'll just stick to my old Snap On light to set initial timing.

Dale McIntosh
TC Gold #92/ACES #1709
67SS & 67 Elky

Dec 1st, 01, 8:26 PM
According to Ignitionman the only rollback lights that work with modern ignition systems are the high end digitals like Snap-On, or MAC. He said the others, (dial type),will be off by 4 or 5 degrees when you are at full advance.

I used a friends Snap-On digital a couple of weeks ago. See link below for an example. Got to say it was REAL easy to determine when your advance is coming in. It has two digital windows side-by-side, one reads rpm and other reads the advance you have it set at. I wanted to see what my advance was at 2000,2200 2400,2800,3000,and 3200 RPM. This thing made it dirt simple. I just went to my desired rpm and clicked the advance/retard button until the timing mark flashed on ZERO degrees. Then you look to see how many degrees you have the light advanced. Easy, and dead-on accurate.

Yes, you can do the same thing with a degree tape or a degreed damper, but you might need two people to be able to watch the tach and damper at the same time.
Bob Von Kaenel
70 SS 402ci TH400

[This message has been edited by Barista (edited 12-01-2001).]