Jims Solid Tappets

Solid vs. Hydraulic Lifters

Harley engines 1953-up generally work with both hydraulic and solid lifters but swapping solids for hydraulics and vice versa most often results in a change of cam performance. If cams which are designed to be installed with solid lifters are combined with hydraulics the following happens: good hydraulic lifters follow the cam lobe with zero lash and you suddenly end up with a longer duration, or in other words, the valves are opening earlier and closing later wih the same cam. This is because hydraulics compensate for the heat expansion of the cylinders where solids loose lift and duration through lash. For this reason we recommend to choose tappets/lifters according to the respective cam description in the W&W catalog.

If you plan to buy a new cam and new lifters, we feel that some comparison might help because each design has some specific advantages. In general it should be considered that Evolution type tappets (OEM & JIMS) are of a much sturdier design than the earlier Panhead/Shovelhead series.

Hydraulic Lifters

+ quiet operation

+ no valve adjusting service

+ no loss of lift and duration from heat expansion

– higher rpm applications (racing) not recommended

– affected by low oil pressure

– affected by contaminated oil

Solid Lifters

+ safely work in 6000+ rpm (race) applications

+ unaffected by low oil pressure

+ unaffected by contaminated oil

+ long service life

– require regular adjustment

– noisy valve train