Twizzle donated a few scans of the installation instructions
of a Harman 120,
they are kind of hard to read so I added a "translation"
120 Inch Street Assembly Instructions
silicone the rocker gaskets and install rockers on
heads. Install heads on cylinders making sure that the
intake valves are over the larger valve pockets in the
pistons. Use an orange hi-temp O-ring on top of the
cylinder and 2 small black O-rings in the oil return
reliefs in the top of the cylinders. Seal top of cylinders with
orange hi-temp silicone seal being careful not to get
any sealant in the oil return holes. Oil all head bolt threads
then install and tighten down evenly. Re-tighten all head
bolts immediately after firing engine
all pushrod ends, install all pushrod corks,pushrods,
and pushrod tubes. Adjust all lifters then rotate engine
over to check for any binding. We recommend the use of
7/16" dia pushrods to eliminate any rubbing inside the
ignition system with centrifugal advance.
Make up top end oil lines using 1/8" line. Use a tee in
the line coming up from the cases to provide a
separate oil line to each rocker box.
carbs, set lifters, set timing (40 deg. with 1
plug per head and 32 deg. with 2 plugs per head), hook
up oil lines, hook up oil gauge, start engine and warm up.
Check for oil pressure and leaks. If everything is O.K. then
run engine gently for a few miles and check carb jetting.
Be sure engine is not too lean or rich then break in for
200 or 300 miles. Use an oil cooler and 60 wt. H.D. oil.
Use stock H.D. late model 3/4" reach plugs or NGK
B8ES plugs. It is very critical that both carbs open from
an even idle ( set with idle screws and not the throttle
cables ) at an even rate. You can check this by feeling
the temperature of the exhaust at each pipe. The cooler
exhaust is the cylinder that's carb is slow opening. Adjust
throttle cables until both cylinders run evenly.
Grand Prix Racing