[SEL] Fairbanks Morse

[Rob Skinner]

> Hi    can anyone tell me the timing for a 1 1/2 HP headless 
> as the book i have
> says Exhaust opens at 20 degrees before outer dead Centre and 
> closes 5 degrees after inner dead Centre and the igniter 
> snaps at 20 degrees before inner dead Centre but the two 
> cannot seam to work
> unless the trip arm on this engine is to long                 
>                Thanks  Nick  

Hi Nick,
There IS the possibility that some prankster has surreptitiously switched your
pushrod while you were sleeping  ;-)  

I'll bet that your engine just needs a little bit of adjustment.  First off,
forget about the ignition timing.  That's the last step.  Since you seem to know
about measuring the position of the crankshaft, we won't talk about that,
either.

The problem is probably going to be finding the correct meshing of the crank/cam
gears and the correct valve lash adjustment.  If you've meshed the gears
according to the marks, that's a fine place to start.  Don't bet your life on
those marks being correct.  

Now rotate the crankshaft through all the cycles, noting when the exhaust valve
opens and closes.  Let's say it's opening at 30 degrees before the ODC, and
closing at 5 degress before TDC.  We can see that BOTH valve events are
occurring 10 degrees early.  That tells us that the cam is ADVANCED from where
we want it to be.  Do whatever it takes to unmesh the gears, and then advance
the crankshaft a bit, or retard the camshaft a bit.  Then re-test to see where
things happen.  It's easy to goof up when you're playing with the gears.

Now lets say that we rotated the crankshaft and watched the valve and saw
something a little different.  Lets say that the exhaust valve is opening at 10
degrees before ODC and is closing 5 degrees before TDC.  We are seeing that it's
opening late and closing early.  In an instance such as this, we can DECREASE
the valve lash.  The valve will open earlier, and close later.  

Play with these two variables until you get the valve opening and closing where
you want it.  Also, don't get hung up on the 20 and 5 that are in the manual.
For opening, anywhere from 30 to 0 will be acceptable.  Bigger numbers are
better for faster running engines, smaller numbers are better for slower running
engines.   

Now that you've got the valve timing exactly where you want it, move on to the
ignition timing, but don't touch the two variables that you've just set.  You'll
have her dialed in in no time.  

Rob


=-=-=-=-=-=
Rob Skinner
La Habra, California
www.rustyiron.com