Timing Light Accuracy

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mopowers

mopowers

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Do inductive timing lights ever go bad and give off inaccurate flashes? I've got a vintage Craftsman chrome inductive light that I'm questioning because of how much initial timing my 340 wants. I've verified the TDC mark - it's spot on. Maybe this 340 just an anomaly because it seems to want 30* initial adv.

Without having a second timing light to check it against, I'm curious if these thing ever go bad.

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Is it a dial advance light. Those can get out of calibration. The plain ones usually not.
 
I have the same light. I have been using it for 40 years, only thing I have ever had to do was re-solder a joint inside.

if you want to do a rough calibration / check, find a computer controlled car and check its advance. this may or may not work. I had an older car that I could do this with.

mopowers said:
Maybe this 340 just an anomaly because it seems to want 30* initial adv.
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I would think you have other problems like no vacuum advance?
 
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I’ve got that same lite and every so often it goes out of wack. Dampness or dropping.
It’s a pretty simple system inside.

When it goes crazy just put it back on the shelf and grab the other one. They are like 25 years old.
 
mopowers said:
Do inductive timing lights ever go bad and give off inaccurate flashes? I've got a vintage Craftsman chrome inductive light that I'm questioning because of how much initial timing my 340 wants. I've verified the TDC mark - it's spot on. Maybe this 340 just an anomaly because it seems to want 30* initial adv.

Without having a second timing light to check it against, I'm curious if these thing ever go bad.

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Some lights have an arrow on the plug wire clip and if pointed the wrong way it will give erratic readings.
 
Electrolytic capacitors have about a 10 year life then they start drying out, breaking down inside and not working as well as they should. After 25 years you could change them, they are very inexpensive if you really like the lite or just buy a new one
 
I guess I'll have to see if one of my neighbors has one I can borrow to see if it'll give the same reading. Thanks guys.
 
Had a nice Fox Valley I used for years until I built a race car and started to question the accuracy of my old light because of a comment by MSD. Bought a new MSD light. Don't know if it is better- But I feel better.
 
mopowers said:
I guess I'll have to see if one of my neighbors has one I can borrow to see if it'll give the same reading. Thanks guys.
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What ignition system are you running. Multispark can mess with most lights.
 
toolmanmike said:
What ignition system are you running. Multispark can mess with most lights.
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The ignition is a GM HEI module, Mallory-style MP electronic distributor, and MSD blaster SS e-core coil.

Murray said:
Had a nice Fox Valley I used for years until I built a race car and started to question the accuracy of my old light because of a comment by MSD. Bought a new MSD light. Don't know if it is better- But I feel better.
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Did you ever check one light against the other?
 
I've had that same timing light for over 30 years & mine is still dead on. Just FYI, I keep it in the box with a desiccant bag that I change out a couple of times a year.
 
I have an OTC dial back that goes awry and another digital one (made by OTC as well) with a tach that gets funky on occasions...
I would like to know how to fix or send them back to OTC for repair.
 
Murray said:
Had a nice Fox Valley I used for years until I built a race car and started to question the accuracy of my old light because of a comment by MSD. Bought a new MSD light. Don't know if it is better- But I feel better.
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They feel better because they got your $$$, I have a old fox Valley also and I still like it better than any other because the advance wheel is at your finger not a dial on the back
 
When they start to go bad, what are the symptoms? Erratic timing? stable timing, but a given amount off? non-functioning light bulb?

Mines pretty stable, so it's hard to believe that it would just flash at the wrong time, but who knows... I just wish I had another hot rodder who lived near me. Hell, someone who even knows what a timing light is would be nice. lol
 
mbaird said:
I have an OTC dial back that goes awry and another digital one (made by OTC as well) with a tach that gets funky on occasions...
I would like to know how to fix or send them back to OTC for repair.
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Probably cheaper to buy another one than send back. Seems like if you send something back for an intermittent failure they won’t find it and will just send it back to you, unless you are lucky and they send you a new one. You eat the postage and fees and get nothing.

You may be able to take them apart and spray the switches ( and probably all of the insides) with some contact cleaner. Most of the time it seems like it is the moving parts that go bad.
 
Mike69cuda said:
Probably cheaper to buy another one than send back. Seems like if you send something back for an intermittent failure they won’t find it and will just send it back to you, unless you are lucky and they send you a new one. You eat the postage and fees and get nothing.

You may be able to take them apart and spray the switches ( and probably all of the insides) with some contact cleaner. Most of the time it seems like it is the moving parts that go bad.
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You may want to check with OTC. If it's a older model many repair parts aren't available but they may offer a new model for a discounted price.
 
does it kick back during cranking?
Every combo is different, but 30 seems to be a lil much at a normal 750 idle.
But you can't always give her what she wants at idle, because it will be too much everywhere else. Actually I would say that you can rarely give a street engine the idle timing it might like. And there is nothing wrong with that, especially if she's an automatic with a hi-stall. Just be sure the power timing does not exceed the ability of chosen fuel to withstand detonation. Which usually falls around 36*@3600 depending .....
 
There are possible errors in timing lights. The trigger mechanism for the flash can introduce delay. A flash tube is supplied a voltage of a few hundred volts by a charged capacitor, a third connection provides trigger at a few thousand volts.

A scope with two channels can be used to measure delay between the real ignition event, and photo transistor signal resulting from flash event. Delay error increases with RPM.

Inexpensive clamp-on lights are often polarity sensitive at the clamp. Clamps are typically marked to show side that goes to plug. Incorrect clamp, results in failure to trigger, or significant error.
 
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My biggest problems with timing lights through the years has been those whose wiring harness plugs into the light and is detachable. Seems the plugs always get loose and then make poor contact. Then, that's when you start having trouble with loss of signal, weak signal, inaccurate or no flash.

Now, I will only buy timing lights that first, have the wiring harness made into the light and secondly do not have a dial back feature. The engine is the best dial back unit you have. Simply use it for that feature.

Believe it or not, I found a vintage tuneup kit at a yard sale a while back. It has timing light, dwell meter, vacuum gauge, compression tester and a hand held remote starter switch. Made by Dixco. Remember them? The light thus far has worked well. It seems to be accurate based on the vehicles performance I have used it on.
 
Here is my $0.02. Timing lights are not very expensive. If yours is old and you no longer trust it, get a new one.
 
I found a buddy with a timing light. I'm going to snag it this weekend and check it against mine. I'll report back with results.

AJ/FormS said:
does it kick back during cranking?
Every combo is different, but 30 seems to be a lil much at a normal 750 idle.
But you can't always give her what she wants at idle, because it will be too much everywhere else. Actually I would say that you can rarely give a street engine the idle timing it might like. And there is nothing wrong with that, especially if she's an automatic with a hi-stall. Just be sure the power timing does not exceed the ability of chosen fuel to withstand detonation. Which usually falls around 36*@3600 depending .....
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It does not kick back at all with 30-32* initial - even when hot. Cranking compression is 162-168 lbs. I've run it WOT with up to 40* total (with my light) and no signs of detonation.
 
mopowers said:
I found a buddy with a timing light. I'm going to snag it this weekend and check it against mine. I'll report back with results.



It does not kick back at all with 30-32* initial - even when hot. Cranking compression is 162-168 lbs. I've run it WOT with up to 40* total (with my light) and no signs of detonation.
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With what fuel,heads, and Q; might I ask?
 
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