In another thread Dave Ray claimed that his timing light showed a 6 degree error when used with distributor ignition systems. I know Dave is really sharp on this and think it needs more discussion so we can understand this better. All the engine guys I have worked with have used these lights for years on distributor systems. I have used one for a while also. The question is how do we determine if the light accurate or not? This could be very critical.
Doug, I agree with you,especially since I was just about to go buy a Sears dial-back lite. I've been using the non-dial back lite from Sears for over 15 years. Just about everybody I know has the dial-back lite and I just wanted to keep up with the times,I've never heard of anyone ever saying negative things about it till Daves post. Now,I don't know what to do,but would like some more imput from other members.Anyone else have any comments????o No:
I am dumb Could someone explain what a dial back timing light does. I have heard of them but am unsure of what is is or does. Thanks, Jeff
Re: I am dumb Jeff, A dial back light enables you to read the engine timing at any RPM. Once the mechanical and vacuum advance start working, the damper mark quickly moves above the timing tab. Once that happens you don't know what your timing is. On a dialback light, there is a dial that enables you to move the damper mark, electronicaly, back to where you can see it. The dial has a scale that reads degrees. You simply move the dial and watch the damper mark. It will move down, and once you line it up with 0 on the timing tab, you simply read the advance off the dial. This can be done at idle speed or any RPM to tell you exactly what your advance is at that RPM. For instance, say you wanted to map your timing curve. You could dial the light back at idle, then have a helper raise the RPM's to 1000, dial it back, then raise to 2000, dial it back, and so on, until the damper mark moved no higher. When the mark moves no higher, all your advance is in. Write down the degrees at each RPM step, and you have your timing curve. Or if you wanted a specific amount of total advance, you could set the dial for that advance, say 32*. Then rev the motor until the mark stops moving up, turn the distributor until the damper mark lines up with 0, and you've got 32* total. Hope that explains it.
I have a Sears dialback light, and a Snap-on, top of the line dialback light. They are very close. I'm sure it is possible that some Sears lights may be off. Who knows what can happen from abuse or what not. But most guys at the track have that Sears light, if it was that off routinely, I think alot of guys would have problems. Marking the balancer 1.76" clockwise around will give you a 30* mark to use, to set up total timing(with a standard light). You have to be really accurate in measuring around that balancer though. That's not the easiest thing to do when it's on the car.
Thanks Larry, I get it now. I have been having trouble with my light. It will flash sometimes and sometimes not. I went tonight and got the Sears light. Thanks for the info.
I'm using a Sun timing light that I bought off ebay. I think its from the 70's, but it was a new, never used piece. Anyone know if these were considered good, accurate guns? It seems to be built well. I love the heavy chrome housing.
