Eng Timing

[davevramp]

What is the best way to time a c145. What timing device do you use, Time Rite, E25 TIMING INDICATOR, or case crank marks? Any procedure or tricks would be appreciated.
Thanks
Dave

[Bruce Fenstermacher]

There are several tools and techniques to timing an engine. The more precise or careful you are the better off the engine will perform. This only makes sense.

Having said that the engine will run quite well with very crude timing and if the procedure is done carefully you probably won't be able to tell the difference from the pilot seat.

I use the crank marks and the case halves as was intended. I have a pointer I made by taping a piece of thin plastic sheet like a credit card to the end of a plain nut. A nut flat is held against a case half with the card at the case half pointing 90 degrees to the crank mark. This is just a pointer which is just a bit more precise that eyeballing it which I've seen many a mechanic do.

I use an inexpensive timing light buzz box that can be purchased as a kit or bought built. My wife bought me mine built for Christmas. Here is a link to the box http://www.magnetotimer.com/ and here is more info on it http://www.rvproject.com/20051009.html.

I'm personally very anal when I time my engines using these tools. I drive my supervising IA nuts demanding near perfection with RPM drops.

My Cub is currently timed so precisely using these tools that at a Mag check an RPM drop is hardly detectable between mags and we routinely shut off both mags to make sure the p-leads aren't broken.

[GAHorn]

...My Cub is currently timed so precisely using these tools that at a Mag check an RPM drop is hardly detectable between mags and we routinely shut off both mags to make sure the p-leads aren't broken.

EXCELLENT TECHNIQUE, Bruce!

Folks, what Bruce is slyly saying is this: If you ever notice no difference between your magneto's during a runup...it's possible that one of your mag P-leads is broken/inop or your key-switch has failed. An easy way to check it out, is while at idle, switch BOTH mags OFF to see if your engine dies. It should!
If you decide not to let it completely shut down, then be very CERTAIN to switch it back on IMMEDIATELY and with the throttle at IDLE. (If ever you should accidentally switch both mags off during a runup...the safe thing to do is LET IT DIE and then do a restart. Otherwise you risk injury to your crank counterweight bushings by slamming them back and forth, and you risk injury to your mufflers with built-up fuel vapors which can then explode and wreck your mufflers/baffles. This is evident during annual when you notice your muffs have an imploded appearance to them due to oil-canning action in response to the explosion.)
Make it a habit to periodically check your mags by switching them completely off and confirming that both mags shut down.
Thanks Bruce for reminding us all about this.

[Lee]

I flew T-28s a bit in Training Command and this was something I think we did at the end of every flight. I do this just prior to shutdown on my -170 ... at any rate, I picked up the habit somewhere and I think the safety aspect is worth thinking about. R/Lee

[N2255D]

I flew T-28s a bit in Training Command and this was something I think we did at the end of every flight. I do this just prior to shutdown on my -170 ... at any rate, I picked up the habit somewhere and I think the safety aspect is worth thinking about.

We did that and checking 121.5 before shutdown when I was fling Military Aero Clubs. Still do it.