The Case for Timing (Lights)

I remember my first timing light, it wasn’t much to talk about and how accurate it was is something I will never know. It was a cheap tool and didn’t last very long but the Motors book I had said the Ford engine had to be set at the following:

Point gap = .015
Dwell = 27
Timing = 6 deg BTDC

Right, well I knew what a point gap was but what the heck was Drell? And 6 deg BTDC? All I knew for sure was that when I connected the timing light and pulled the trigger on it, a light flashed. You see here’s the problem, when I started out working on cars there was no YouTube or Internet, email wasn’t even a thought at the time. I had a Motors manual as a guide and that was about it. I finally talked with a neighbor that had some amount of automobile knowledge and he told me how to use the timing light. It was still a long time before I really understood what Dwell and BTDC meant but I actually thought I knew something about setting the timing on an engine at this point.

Then we move forward to today and most modern engines if not all of them now have their timing controlled by a microprocessor or in other words, a computer. In fact, it is programmed to change this timing figure based on input it receives from various sensors mounted to the engine. These can provide information from coolant temperature to the required fuel mixture depending on speed, fuel amount required and the quality of the fuel. In essence, it has for all intents eliminated the need to pull out the old timing light and do any checking. We change the spark plugs at 100,000 miles and simply call it good.

So my case for timing lights really comes down to using them for performance engines. I am constantly amazed at the number of racers at our local dragstrip that simply have no idea of how or why they perform a timing check, nor do they have much of an idea of the effect that changing the timing of an engine can have on its performance or lack thereof. But it is rather easy to get in the familiar process of setting an engine to a certain timing number and then just leaving it there. We say the engine seems to run it’s best at this number and we can find no reason that we should check it again and again but honestly it is something that we should look at far more often than we do. It can be an early warning of something going amiss in the valve timing or simply a part that is on the verge of failure. And if used properly, it can add a great deal of longevity to our racing engines. I know for a fact that someone, somewhere will ask someone this basic question this week – “the engine is a blah with blah-blah – how much timing should I put in it?”. Well, the answer is one that needs to be worked at and starting off with a baseline number is fine but finding out exactly what the engine wants on a given day at the track is a trial and error situation until you build historical data on that engine. So what you really should be doing is setting the timing to a baseline number, make a run and noting if there were any issues during the run, then increase the timing amount by 2-4 degrees and repeat the test process. To be very accurate about it, once the speed or elapsed time no longer improves, then you would want to back off the timing one degree for each test until you see another change in the test results. At that point, you increase the timing by 1 degree and should be at the optimal timing setting for the engine. Taking notes on weather, track and other settings of the vehicle will help you build the historical data that will allow you to readjust the timing quickly within the same conditions.

Timing is also an important factor in the typical hot rod engine used on the street. And when I say typical, I am talking about one that still uses an engine mounted distributor to move the spark energy to the spark plug. Most of the time, these engines are equipped with a carburetor and there are normally three elements of timing involved. Those are static timing, mechanical advance and vacuum advance. All three of these elements need to be fine-tuned to the engine combination and the vehicle in which it is used. Failure to miss on any of these elements can result in an engine that simply doesn’t start correctly and certainly, will not run very well. And just a note, unless an aftermarket engine balancer (harmonic balancer) was used during the build of the engine, you will need to install a timing tape so that you properly read the information that the engine is providing you. Next time around we will go through the proper procedure for a street style Chevrolet engine and we will do a review of the battery-powered timing light sold by Amazon.


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