Timing

[Sheldon]

My 0-360's data plate timing is 25 deg.... The internal timing of the Slicks attached is 20 deg... This is how my engine came, timed at 25... Why the difference?... Should the timing of the engine be reset to 20 deg also or leave as is? Or are these timings independent...??
Thanks, Sheldon

[Radomir]

Are you talking about the "lag" on the impulse coupled mag? Either way, don't change the mag timing.. 25 is it, just as the data plate says..

[Mel]

Radomir has it right. Just make sure that the impulse coupling has "tripped" when checking the timing. i.e. turn the prop until the coupling trips, then move it back to the 25 degree mark.

[osxuser]

I've seen this before, not a big deal unless you are hand propping the engine, but I'd still rather see the right lag impulse couplings on a mag. My worse case of this is the 25? lag mags on an engine that is running the timing between 30? & 32?. It can be a scarey thing to prop that thing when it's hot, but I haven't lost a finger yet.

[Larco]

Hi Sheldon, I hope this helps. The engine will be starting at 5 degrees BTDC with a 20 degree lag mag if the timing is set at 25 degrees BTDC. Our Baby ran fine this way for years. If memory serves me correctly, A 4371 mag has a 20 degree lag and a 4373 mag has a 25 degree lag. Have worked on many RV's and they seem to come both ways and all seem to work just fine. Larry Hey! I was there last. :-)

[hecilopter]

came with the 4371 mags with the 20 degree lag. I thought I read somewhere it was because I have the SkyTec starter which spins much faster than a standard one, thus it releases the impulse 5 degrees early to let it fire TDC because it is spinning so fast. Anyone recall something like this?

[Sheldon]

Thanks guys... I just rebuilt my Slicks (500+ hr inspection).. Back on and timed to engine 25 deg... as was... ran fine.. I was just wondering why...I appreciate the responses and info... Thanks, Sheldon

[MIKEM]

When I saw hand proping mentioned I wanted to jump in and put in my two cents worth. To minimize kick back and the right mag firing early, It is important to note that if you do hand prop you should put the key switch on the left mag only and after the engine starts then switch to both, this is automatically done for you when you use the key to start normally, the key start position bypasses the right mag. Some engines have two impulse couplings in which case for hand proping you can put the key switch on both. To answer you question, no I didn't learn this the hard way.

[aerhed]

Sub-zero hand propping is the world's greatest abdominal builder. If I could only get Chuck Norris to sell it. "The Abprop"? "Gutflex"?