Last spring, my friend Steve Anderson asked if I was interested
in restoring a HP Briggs & Stratton Model FH. Since I’ve
never been up-close and personal with one of these old ‘vacuum
pumps,’ I readily agreed, thinking the restoration would make
for a nice spring project. As a self-taught machinist (and I still
have all of my fingers!), I’ve read a lot of books and asked a
lot of questions. I have several home-built hit-and-miss and
Sterling engine models under my belt, so when Steve asked me to
restore this little Briggs & Stratton, it was an offer I
couldn’t refuse.
Getting to Work
The Model FH was mostly complete when I took it from Steve. A
cursory exam revealed the exhaust valve pushrod and the choke tube
were absent, and most of the threaded fasteners were loose. Upon
disassembly, I found the oil pump plunger was missing, the gas tank
was rust, and the carburetor’s mounting flanges were
broken.
Steve gave me the original operator’s manual and parts list
for reference, which claimed the Model FH was equipped with a
four-bolt head. But curiously, this engine only has two head bolts,
which seemed a little strange to me since the manual and engine
should be consistent. I e-mailed Charles Camara of CPC
Reproductions, who sells Briggs & Stratton parts, and he told
me Briggs & Stratton often used spare castings from the factory
on later models, and that the FH’s crankcase probably came from
a Model FC.
Unsure exactly what to make of this revelation, I happened to
read on the Internet that early F series engines had the model and
serial number stamped on the crankcase, while later FH models had
this information on the brass tag affixed to the shroud. With that
in mind I began cleaning up the crankcase, and sure enough I found
the engine’s serial number, FB3535, stamped there.
Internet information also indicated that early FHs used slanted
cylinder fins and a bronze carburetor. This engine has the slanted
fins, but the carburetor is made from pot metal. But that
wasn’t the full extent of things, as this engine also has a
3/16-inch-wide piston ring, and the oil pump
plunger is operated directly from an eccentric on the crankshaft,
not from a cam follower as my research indicated. These
contradictions still perplex me, and make this engine seem as if it
were some sort of mix between a Model FC, FB and FH. I like to
think of it as a Model FH mutt.
Fix Her Up
After the age-old routine of degreasing and cleaning the
FH’s parts with a wire brush, serious restoration began with
removing the rust from the base-mounted gas tank. Because the gas
tank is nearly inaccessible, I found it impossible to scrape or
wire brush all the surfaces, so I resolved to try the electrolysis
cleaning process I had learned about on the Internet.
I hadn’t tried the electrolysis method before, and I must
say it worked very well, albeit fairly slowly since I used a
12-volt battery charger. A 24-volt charger would have sped up the
operation considerably while still maintaining a relatively safe
open-circuit voltage. Once the rust was gone I coated the entire
inside of the tank with some of Lee Pederson’s gas tank sealer
to prevent any rust from returning any time soon.
The next step in my restoration was to free up the valves and
lap them to get a good seal. I had no problem removing the exhaust
valve, but the intake valve’s stem is peened over to secure the
spring washer, so I lapped the intake in place. That made cleanup
after lapping more difficult, but it was nothing 1 couldn’t
handle.
I tackled the broken carburetor flanges next. The flange was
broken into two loose pieces on the left side, and on the right
side the broken flange piece was missing. I repaired the left side
by first super-gluing the two pieces in place. I then connected
them to the carburetor by making a fillet on top with JB Weld. On
the right side, I drilled, tapped and lock-tighted a 2-56 screw
into the flange base, leaving the screw protruding about a -inch to
provide extra support in anticipation of my next step. I then
carved a flange mold out of a paraffin block to the proper outline
and dimensions of the original carburetor base, clamped the
carburetor to the mold and filled in the missing flange area with
JB Weld. Presto, I now had a new flange that not only looked great,
but also worked great.
I replaced the missing oil pump plunger with the shank of a
‘Q’ drill bit, which provided the desired degree of
hardness and finish. I cleaned and adjusted the points, replaced
the leaky condenser and deteriorated spark plug wire, and
fabricated a new pushrod. The original wrist pin had worked loose
at some time in the past and was bent, slightly scoring the
cylinder. Luckily, the cylinder didn’t appear to be terminally
scuffed, so I lightly honed the cylinder wall. Next, I fitted a new
wrist pin and then made an ill-advised decision to reassemble the
engine with the original piston ring. I didn’t know it at the
time, but that oversight would later turn into a major
headache.
The Road to Restoration Gets Bumpy
Adding insult to injury, I also challenged Murphy’s Law …
and lost! Despite the fact I’ve never done restorations this
way before, I painted the entire engine my favorite color of blue
before reassembling it. The weather was nice that day, I thought
‘what the heck?’ Little did I know that fateful decision
would have implicit repercussions. Murphy says that an engine is
73.8 percent less likely to run if it’s painted before it’s
operational. He’s right: The engine looked great, but it
didn’t run.
Breaking Murphy’s Law was a bad omen. I encountered a major
problem upon re-assembly when the flywheel magnets dragged on the
coil pole, inhibiting the engine from turning all the way over.
This was apparently the result of slight wear in the crankshaft
bushings, which made the crankshaft displace just a bit. I called
Richard Reller, a helpful engine buddy I’ve consulted in the
past, and he suggested I sand down the coil pole pieces that were
interfering, using Hi-Spot Blue to spot my work. It took a long
time, but it worked perfectly and eliminated the interference.
My streak of bad luck continued, however (Murphy, why do you
torment us old-engine restorers?). Once the flywheel was
functional, the magneto wouldn’t produce a single spark.
Clnsure of what was the problem, 1 eventually checked the coil and
realized the secondary circuit was open. I should have known, but
oh well, we grow too soon old and too late smart.
I converted the engine to battery ignition using the existing
points and condenser, which resulted in a great spark. But Murphy
still wasn’t appeased: The engine wouldn’t run. The old
piston rings resulted in low compression, and a sticky intake valve
made the situation worse.
Enough of the Games
Tired of the cat-and-mouse game I was playing, I completely
disassembled the FH again with the determination to do it right.
First, I removed the intake valve by grinding off the peened end.
The stem was rusty and badly pitted. I substituted an intake valve
with the correct stem and head diameter from a similar, later-model
Briggs & Stratton. I cut the new stem to the correct length and
cross-drilled it to take a cotter pin to retain the FH’s
original spring. After lapping the new intake valve, it operated as
good as new.
Next, I carefully checked the piston. I’m glad I did because
the ring-to-land clearance was 0.005-inch on one side and 0.01-inch
on the opposite side. The uneven wear was probably the result of
the bent wrist pin causing the piston to slightly cock to one side
as it worked. To correct this, I chucked the piston dead true and
squared up the ring groove. Once accomplished, I needed a piston
ring 1/64-inch wider than the original
3/16-inch size.
Another Web site gave me the idea of using two rings together in
one groove to achieve the desired width. To get the
13/64-inch width I required I combined a
1/8-inch ring and a
5/64-inch ring in the correct diameter.
Additionally, this solution separated the end gaps by 180
degrees.
At this point, I finally got the gumption and confidence to
reassemble the FH. But before I made an attempt to start it, I
fabricated a short choke tube using copper tubing and fittings and
appropriated a shaft and choke plate from an old weed trimmer
carburetor, which I secured with nylon cable straps.
It’s Go Time!
After all of the problems I had experienced, I was finally ready
to start the Model FH. After one quick shot of starting fluid, the
old engine immediately jumped to life on the first try and
continued to run smoothly using battery ignition. A little later, I
replaced the battery with a good coil. Now the FH runs well in its
near-original configuration. 1 say ‘near-original’ because
the purists among us will quickly point out that the muffler is the
wrong type, the choke tube isn’t exactly correct, and so forth.
To this I reply that if an engine looks like a FH and sounds like a
FH, it must be a FH – even if it doesn’t have all the expected
characteristics.
This engine came together thanks to a unique combination of old
engine technology, modern Internet information and, best of all,
helpful advice from several new-found old-engine enthusiasts that I
now count as friends. Despite the restoration’s rocky road and
my personal run-in with Murphy’s Law, I learned a lot and had
fun working with an old engine I previously had never encountered.
I had to give the engine back to Steve, but the experience will
stay with me forever.
Contact engine enthusiast Ken Hollenbeck’s at: 607
Cherry wood Lane, Sister Bay, WI 54234; (920) 854-2461.
