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SETTING VALVE LASH
FOR MECHANICAL TAPPET CAMSHAFTS |
| What is the BEST method of
where to position the crankshaft rotation and piston movement when
adjusting the COLD VALVE LASH? Most methods refer to the FIRING ORDER to make the job FASTER. Do not fall for this shortcut unless you are sure of the length on the RAMPS. If the ramps are "LONG" like the Chevrolet V8 small block mechanical tappet camshaft part number 3849346. This part number is sometimes refered to as a "30 30 DUNTOV". The 30 30 refers to the factory's valve lash of .030 inches on both the intake and exhaust. The "TOP DEAD CENTER" method will not work with camshafts that have these types of ramps! The ramp of this camshaft extends to 135 CAM DEGREES on the opening side and 137 cam degrees on the closing side of MAXIMUM CAM LIFT. I suggest the following method for finding the "BASE CIRCLE" of the camshaft lobe so that the valve lash will be accurate. To set an INTAKE valve, rotate the engine so that the EXHAUST valve of the SAME CYLINDER just: "STARTS TO OPEN". To set an EXHAUST valve, rotate the engine so that the SAME INTAKE valve of the SAME CYLINDER goes thru full lift and then is: "ALMOST CLOSED". This method will require a lot
of crankshaft rotation but is the BEST METHOD IN MY FIFTY YEARS OF
EXPERIENCE in assembling engines and working with other engine builders. |
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Copyright © 1999-2007 by harvey CRANE, Inc. All rights reserved.
Revised:
07/12/08 09:27 AM