quote:
Originally posted by No Quarter:
George, sounds right, but how that's possible without breaking the laws of physics is beyond me
Its possible because hydraulic tappets collapse.
quote:
Originally posted by No Quarter:
Any views on how to adjust the rockers? Googling some say 1/4 turn, some 1/2, some 1/2 to 5/8.
From sticky #3
One rule of thumb for adjusting hydraulic tappets is to compress the plunger 1/2 of the plunger’s available travel; however it is important to measure the travel of the plunger if that’s your plan. The plunger of a modern hydraulic tappet does not compress as much as the plungers did decades ago. The plunger travel of a Crane roller tappet is only 0.062”. The plunger travel of a 1995 Johnson HT900 tappet I have on hand is 0.125”, whereas the plunger travel of a 1970s vintage HT900 is tappet is 0.187”. I am told the plunger travel of a typical modern hydraulic tappet is in the range of 0.060” to 0.080”. Nowadays the recommended range of hydraulic tappet adjustment when using stud mounted rocker arms is 1/8 to 1/2 turn of the adjusting nut beyond zero lash when the engine is hot (adjustable rocker arms are usually mounted on studs with 3/8-24 or 7/16-20 threads). Decades ago the spec for adjusting small block Chevy tappets was one full turn beyond zero lash, which was supposed to set the tappet plunger in the middle of its travel! This means the plunger in Chevy’s tappet had 0.145” of travel.
The amount to adjust a stud mounted rocker arm beyond zero lash – engine hot
1/8 turn = high performance motors with adjustable valve train
1/4 turn = high performance motors with non-adjustable valve train
3/8 turn = sets many modern tappets at half collapsed
1/2 turn = maximum adjustment, do not exceed 1/2 turn
The relationship between stud mounted rocker arm adjustment and tappet plunger compression
Turns on Adjusting Nut | Adj. Nut Movement | Actual Compression of the Tappet Plunger
------------------------------------------------------------------------------------------------------------------
1/8 turn ______________ 0.005” to 0.006” ______________ 0.009” to 0.010”
1/4 turn ______________ 0.010” to 0.012” ______________ 0.017” to 0.021”
3/8 turn ______________ 0.015” to 0.019” ______________ 0.026” to 0.033”
1/2 turn ______________ 0.020” to 0.025” ______________ 0.035” to 0.044”
