In Tune With The Times: Figuring Timing Lights

As we pointed out in the first segment, this vintage Sears timing light has proven to be accurate and reliable.

“Who cares about timing lights? I’ve timed the engine in my race car a thousand times.  It runs right; It doesn’t sound like it’s detonating; What more do I need to know?”  There’s no question that timing lights are anvil-basic devices and are easy to use, but contrary to what you might first think, all timing lights are not created equal.  Before we get into lights, think about this: The idea behind setting initial timing is to synchronize the firing “point” of the ignition with the position of the piston in the cylinder bore.  In order to establish this synchronization, you use a timing light to determine piston position relevant to a number of degrees marked on either the harmonic damper or the timing tab.  The only real problem with setting up timing in this manner is the fact that your timing equipment must be absolutely accurate.  Correctly indexed harmonic dampers, as well as properly indexed timing tabs, are crucial.

While it might come as a surprise to most serious racers, some (no, make that many) timing lights are not accurate! The reasons are varied, but in the majority of cases, timing lights have been designed for use in “more pedestrian, Mom and Pop” applications.  Most tune-ups (professional and otherwise) seldom, if ever, require that the timing be checked beyond 2,000 RPM.  As a consequence, many timing light manufacturers are able to construct a very simple, cost-effective timing light.  And the key here is “cost-effective”.  In some instances, a trigger delay is installed in the light (this practice is even found in some very high dollar “professional name brand” lights.  I won’t name them.  Just think mega buck).  This has little impact in the lower engine speed ranges, but once the RPM level goes over the 2,000 RPM range, timing lights with delay circuits appear retarded.  Another real problem is radio frequency noise protection.  Most home-use timing lights have little if any protection against RF noise and as a result, can produce erroneous readings when used in conjunction with solid core wire sets.

According to MSD research, certain types of timing lights with built-in adjusting mechanisms (usually the common “dial back” models) have been proven to be so inaccurate that they produce false readings at speeds in excess of several hundred RPM.  Many of these adjustable timing lights also carry very high price tags.  Before you purchase such a unit, compare it to a known timing light.

That’s not the end of it, either.  Next issue, we’ll look at ways to test your timing light.  We’ll look at the right way to use your timing light, because, believe it or not, there are some misconceptions out there.  Watch for it.

This is an old Sears timing light I regularly use. It's reliable and accurate.
This is an old Sears timing light I regularly use. It’s reliable and accurate.

 

 

 

Both timing light power cables should be affixed to the battery. In the event that your race car has a trunk mount battery or pair of batteries, add a power junction block to an accessible location in the engine compartment. Never use the coil as a source of timing light power.
Both timing light power cables should be affixed to the battery. In the event that your race car has a trunk mount battery or pair of batteries, add a power junction block to an accessible location in the engine compartment. Never use the coil as a source of timing light power.
Number One ignition wire must be well separated from the other wires on the engine. Spark cross over from other wires can easily influence timing light performance.
Number One ignition wire must be well separated from the other wires on the engine. Spark cross over from other wires can easily influence timing light performance.

 

 

Copyright © 2005-2017 RacingJunk.com All Rights Reserved.

Designated trademarks and brands are the property of their respective owners. Use of this Web site constitutes acceptance of the RacingJunk.com
Terms of Use, Classifieds Disclaimer, Privacy Policy, and Cookie Policy