AMS Johnson-Hylift Lifters
for all Twin Cam Harley engines
From 1999 - 2001, Johnson-Hylift supplied lifters to Harley-Davidson...
Johnson-Hylift designed and produced a special piston and valve body
to work across the temp ranges and varying oil psi typically encountered
on an air-cooled engine such as the Harley. Since late 2001, HD has used
Delphi brand hydraulic lifters. That's why there was a Harley p/n change
from 18538-99 to 18538-99A and now 18538-99B. However, Delphi did not
use a 0.655" hi-volume / hi-pressure plunger piston and valve body
specifically designed for Harley as found in the Johnson-Hylift lifters.
Instead, Delphi essentially used a small block Chevy lifter. The main
difference is the Delphi lifter tries to boost the hydraulic psi by decreasing
the piston diameter, but this leads to a smaller high pressure oil reservoir.
The volume is too small and allows the lifter to clatter. That may be why
so many of the late model Twin-Cam bikes are noisy. After doing some
research AMS learned these Delphi version 18538-99B lifters are made too
small to stand up to Harley's heavy valve spring pressure. The oil reservoir
inside the lifter is too small. It doesn't hold enough oil to let the lifter bleed
off under normal use and still have a cushion of compressed oil to take up
valve train slack. Note: ALL lifters bleed off during operation and even
more-so when the bikes sits, engine off.

AMS went back to Johnson-Hylift's Chuck Hicks, the original
manufacturer / engineer of the earlier HD 18538-99 lifters, which
don't seem to be as noisy as those made by Delphi. Working with Chuck,
AMS modified a Johnson-Hylift lifter, to accept a very precise check valve
from an A900 Ford Mustang lifter. Then we used a large plunger that
allows more oil reservoir volume, and a ball seat that fits much tighter,
yet has an oil feed groove to allow more upper rocker box oiling. What
this does is give us a lifter with a much bigger internal oil reservoir that
will keep the lifter / pushrod from bleeding too much and bottoming out.
The bigger reservoir maintains a cushion of oil inside. The ball seat
ensures better top-end rocker oiling and better pushrod tip fit.... all of
which makes for a quieter lifter.

Our p/n for these AMS Hylift lifters is LIF2148. We recommend using stock
non-adjustable pushrods with them... however adjustable pushrods will work
too - but it does require getting the preload set within the .080" to .100" range.

There are a dozen other things that can cause "lifter" noise - it can be coil
bind, rocker to spring cap interference, spring cap to stems / guide length
interference, poor oiling, high lift cam profile causing loft, overheating motor,
wrong oil viscosity for ambient temperatures, aerated oil, low oil pressure,
gear drive backlash, etc. However if you're convinced you've eliminate all of
these things, and the lifters still rattle, then the next step is to try another set
of lifters, preferably the AMS LIF2148's with their larger oil reservoirs. Many
times this will lessen or eliminate the noise.