At last, I finally got the engine rebuilt, and back into the airplane.  The
good news, the engine runs, and it runs good! (see details below).  The bad
news, I did not get a chance to fly yet due to my Rectifier/Regulator
failing (always something), therefore my alternator circuit break kept
popping when I was running the engine.

Below is a fairly long article, but I'll try to describe in detail the best
I can my process, and also some lessons learned along the way, to help
future Revmaster owners.

Quick Recap:  The first week of April 2020, my Bendix D3000 R-magneto
stopped working.  The problem was the cam-mechanism that opens/closes the
points had became damaged, likely due to some corrosion making the points
very hard to open.  I decided on the Simple Digital Systems (SDS)
Dual-Ignition system due to 1) pricing ($925 vs. 1400+ for an IRAN on the
magneto) 2) brand new system, vs. a "refurbished" or "IRAN" magneto 3) more
powerful spark than a magneto 4) the ability for the user to allow for
variable ignition timing (vs. fixed timing in the magneto) and 5) parts
availability (parts are available for the SDS while the Bendix D3000 is
becoming more and more scarce).

Pulling the Engine - Installing the SDS ignition requires the user to mount
three magnets on a rotating device, and mount a hall sensor to "read" the
magnets.  On the Revmaster, this can either be the prop-hub or the
flywheel.  I felt a little more comfortable mounting them on the flywheel,
since I wouldn't have to build a custom mount for the hall effect sensor up
towards the prop hub (I'm not a welder or a machinist, so this would have
been very difficult for me).  However this decision required me to pull the
engine.  With the engine out, I decided to give it a rebuilt, and install
some upgrades as well.

Engine Rebuild: Internals - Once I got the engine home, drained the oil,
and took it apart, I was particularly impressed with just how well the
bottom end has held up.  I didn't notice any scoring, wear, or anything of
concern on any of the main bearings, the crankshaft, or even the connecting
rods.  My engine has approximately 500 hours on it, however after a little
bit of cleaning up, the internals looked essentially new.  This gave me a
whole new level of warm and fuzzy, for just how well designed, and fairly
bulletproof this engine really is.  With this box checked, I turned my
attention to the camshaft.

New Camshaft - I researched some new cams, everything from the Engle 100,
CB2280 Cheater, New Revmaster Cam, and even considered the Engle 110.  I
ultimately chose the CB2232 due to it's shorter duration, and higher lift
over stock.  It is supposed to help lower the power band of the engine to
1500-4500 RPM range, which is the sweet spot for aviation engines.  As
previously stated (in my old post), the CB2280 improves power, but
throughout the entire RPM range, even past 5000+ rpm.  The 2232 improves
the power MORE than the 2280, and puts it right in the 1500-4500 range.

Believe it or not, the camshaft was actually the most infuriating part of
the entire rebuild.  Sounds easy right, just to swap a simple cam?  Wrong.
This is because the stock Revmaster camshaft has the cam gear RIVETED onto
the camshaft.  I tried grinding them down, and punching them out with no
avail, so my solution was to get another cam gear.  Well everything went
great, until I installed the new cam gear on the new camshaft, and realized
that it was about 3mm too thick (when compared to the Revmaster cam gear)
and would not fit due to that extra 3mm riding up against the thrust
bearing  It needed to be specially machined to fit.  Fortunately, I did
find somebody a whole 5 minutes from my house who performed the work, but
it was still rather inconvenient.  Solution:  If you cannot reuse the old
cam gear, order a new REVMASTER cam gear, or be able to find somebody who
can machine an aftermarket cam gear to fit.  Having the old revmaster gear
definitely helps a lot so the machinist can compare.  Be mindful, only the
side of the gear facing the camshaft needs to be cut down.  The rest of the
gear can remain untouched.  With the new cam gear installed, and machined,
I continued the rebuild.

94mm Pistons/Cylinders - I spoke to a machinist in Tacoma WA who
recommended taking 94mm cylinders and having them lathed to fit a 92mm case
since this would leave a little more meat around the case savers.  This is
the route I took and I'm very glad I did, as it prevented me having to have
the case machined.  The gentleman lathed down the cylinders, professionally
balanced the pistons, and machined my heads for 94mm.  Once I got the
internals and camshaft back together, installing the pistons and cylinders
was pretty straight forward.  I did not use the "professional" tool of
measuring deck height, however I set my deck height at approximately
0.05".  This yields a compression ratio (94mm bore, 78mm stroke, and 55cc
chambers) of 9.5.

Cylinder Heads - Ah yes, every VW owner's favorite topic.  While having my
heads machined, the machinist took the initiative and inspected my exhaust
valves free of charge.  And surprise surprise, they were burnt from a lack
of cooling.  I was a little surprised since my engine has NEVER missed a
beat or ran rough, and also that I never let the temperatures get in the
"yellow" (450F) range on the CHT gauge.  The machinist noted that I was
running MOFOCO 041 heads, and had a few choice words regarding them, and
recommended I move up to CB044's or AA Cylinder Heads.  I wasn't about to
get into a war of the words with somebody who has much more VW experience
than me, however I was under the impression that AA makes the same Chinese
DRD heads that Mark Langford had trouble with in just under 50 hours.  I
asked the machinist how long he though the MOFOCO 041's would last, and he
thought with the cooler temperatures up here in WA (where 60-70F is
considered "hot", as opposed to Mississippi where each day was nearly
90-100F), they would likely get through the summer, however he recommended
getting them changed sooner rather than later.  Lessons Learned:  While
they initially seemed okay when I got them in 2019, the MOFOCO 041's still
have their limits and should be kept well below the 450F mark on the CHT
gauge to avoid exhaust valve damage.  I was pleased though, however, that
it did not crack in between the valves like my stock valves did.

Spark Plugs - I re-used my AutoLite 4164 plugs that I installed with my
magneto wiring harness back in 2019.  With ~50 hours on them, they were
slightly dirty, but I cleaned them and re-used them.  SDS does not give a
particular gap to set them to (and if they do, it's not in my installation
instructions), so I just set them to 0.025".

Installing the SDS Ignition - While slightly time consuming, this was
honestly pretty easy.  Obviously I read the instructions about 10x, but it
basically amounts to putting the engine's #1 cylinder at TDC, take a #30
drill bit, dril some holes in the proper locations on the flywheel (or
Prop-Hub/Bolts if you go that route) insert some epoxy, insert the magnets,
and let them cure.  The hardest part was mounting the hall effect sensor,
but even this wasn't too bad.  With the flywheel cover OFF the engine, I
drilled two holes near the top of the crankcase (just above the flywheel),
tapped them, installed some spacers/washers, and installed the Hall Effect
Sensor.  After that I took a Jig-Saw, and took a cut out of the flywheel
cover to account for the Hall Sensor (if anybody wants pictures, I will
gladly email them).  With everything mounted, magnets and sensor, the "fun"
part was rigging up the controller to my Jeep Battery to give it power,
then slowly turning the (Revmaster) engine to ensure the hall sensor can
pick up the magnets.  The SDS controller will tell you "YES" or "NO" if it
can see the magnets, so there is absolutely no guess work at all.  And
there is even some wiggle room involved; I mounted one of my magnets
slightly too low, slightly below the hall sensor, and while I was afraid
that I would have to re-drill another hole in the flywheel, the hall sensor
still managed to pick it up just fine.  Lessons Learned: With the SDS
system, get the magnets as precise as you can, but there is some wiggle
room involved.  In addition, the SYNC magnet can be mounted 60 degrees past
the #1 magnet (as opposed to 40 like the instructions say) and will not
cause any issues according to Ross at SDS.

With the ignition complete, with the help of a friend and Growler NFO, I
put the engine back in the plane.  After some slight starter issues, small
oil leaks, and recharging the battery, the plane came to life.

First Runup:  As soon as the engine came to life, it immediately sounded
deeper and throatier than with the 92mm cylinders and stock camshaft.  I
immediately checked for oil pressure, which came to life at 50 psi like it
did before, which meant that I didn't screw up the oil pump or bearing
clearances.  I let it idle for about 4-5 minutes, then gradually increased
the throttle little by little.  Eventually, after running for about 10
minutes, I slooooowly applied full throttle, Static
RPM, with a Sterba 54" x 54" propeller?!  That's nearly 100-200 RPM more
than I had with the 92mms, stock camshaft, and magneto, and it's not even a
broken in engine just yet!  And while this next part is certainly
subjective (especially since I haven't flown it yet), the engine just
"feels' so much more powerful!  So much that even with full brakes and
chocks it still feels like it is going to move forward!  I couldn't have
been happier at in this moment.

Unfortunately, after letting the engine idle for about 2 more minutes, I
looked down and noticed the Alternator Circuit breaker had popped.  However
this gave me an excuse to run the engine without the alternator and see if
it could last without the alternator.  I idled the engine for about 4-5
minutes with the alternator OFF, shut the engine off to give it a break,
then started it up again for 4-5 more minutes, and then eventually shut the
engine off because I was legitimately getting worried I would kill the
battery.  Bottom line, I made it a solid 8-10 minutes on battery power
alone, and that was even with one start in between.  So that tells me that
if in flight and the alternator were to fail, if nothing else, I would have
at LEAST 8-10 minutes to get on the ground safely.  Eventually I will do a
more thorough test on this once I get my new Regulator/Rectifier, but hey,
this is only the first run up.

To Summarize:

SDS Ignition - Very affordable, great customer service, fairly easy to
install.  I Didn't mention this before, but my G3 spark plug wires that I
bought for my Magneto Harness (last summer in 2019) are compatible with the
SDS system!  A less reputable/honest company would likely have told me "no,
yours won't work, get ours instead", but Ross's honesty saved me about $50
in the process!

94mm Cylinders - Can get lathed to fit in a 92mm case.  Way easier than
trimming the case.

Camshaft - If unable to get the old cam-gear rivets off, get a Revmaster
cam gear, or have an aftermarket one machined.  If I were to do this again
I would get a Revmaster, but my aftermarket one works fine so far.
Remember, only the side FACING the camshaft has to be trimmed, everything
else can be left untouched.  Bring the old gear to the machinist if able.

Pistons/Cylinders - I set my deck height to 0.05" to eliminate as much
squish as I could, while still remaining safe (0.04" is the minimum you
need to be "safe" according to The Samba). This yields a 9.5 Compression
Ratio.  Okay for 100LL, but be very mindful if using auto-gas.

Cylinder Heads - MOFOCO 041's are okay, but just like any head, they have
their limitations in regards to cooling.  Even though Revmaster says
400-450F is in the "green" zone for CHT, this is still too hot and my
exhaust valves showed it.  These heads, however, did not crack between the
valves (one of the big reason I got them to begin with), and have
definitely gave me a power improvement over stock heads.

Spark Plugs - Autolites ($2.99 a piece) held up a solid 50 hours since I
installed them last summer, and are okay to be re-used.  Set gap to 0.025"
for the SDS ignition.

First Runup - Throatier/Deeper sound, and showed an increase of ~100-200
static RPM on a freshly-rebuilt engine that's hardly broken in.  All RPM
aside, the engine felt way more powerful.  With the alternator off, the
engine withstood 8-10 minutes before I shut it off, and the battery still
had cranking power afterwards.  A more thorough test will be conducted in
the future and I will give a more accurate figure.

Closing Remarks - Obviously when the Revmaster 2100D was built, many of
these options were not available, and Revmaster has since made a lot of
these improvements in the R-2300.   However in my opinion, regarding the
2100D, this setup is the gold standard for this engine (although there are
certainly better cylinder heads out there).  The SDS produces a nice
crisp/clean spark, and you can set the timing how YOU want, varying per
RPM, not just fixed like in a Magneto.  The 94mm cylinders and CB2232
definitely add a nice punch, and the engine just feels much more solid with
this setup.  I absolutely can't wait to get this thing up in the air!

One FINAL thing that I should add, regarding the increase in power, is that
if anybody has ever tried turning a Magneto by hand, you'll probably notice
that it's freakin' hard to do.  I don't have any figures to support this,
but this has to take a decent amount of power (maybe 0.25-0.5 HP) to spin
such a heavy, mechanical rotational device.  Now that the magneto is off
the engine, and all the engine has to do is spin a few small magnets on the
flywheel, I would be a fool to thing that this wouldn't contribute to the
total increase in power, scoring another vote for the SDS system.

Expect another (shorter) post next weekend once I install my new TR, and
get this thing back up in the air.

If anybody has any questions, or wants pictures of the process, I'll be
more than happy to help out and send you what you need!  I hope that this
post (whether now or 10 years from now) helps out some Revmaster owners.


Sam Spanovich
74S, Anacortes WA
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