Measuring and testing – Test stand – For engine
Reexamination Certificate
1997-12-23
2001-08-14
McCall, Eric S. (Department: 2855)
Measuring and testing
Test stand
For engine
C073S114220, C033S519000, C033S600000, C033S606000, C033S611000
Reexamination Certificate
active
06272910
ABSTRACT:
TECHNICAL FIELD
This invention relates to a measurement platform device or tool for facilitating the degreeing of a camshaft.
BACKGROUND
In order to determine if a camshaft meets the manufacturer's specifications, a procedure known as camshaft “degreeing” is employed. The procedure determines if, in fact, the valves are opened and closed in the precise, specified manner. This is particularly important where competition engines are concerned, since cylinder pressures/volumes are critical to engine performance. Inaccurate camshafts can rob much needed horsepower from these engines, placing the driver at a real competitive disadvantage.
The problem arises because camshafts may not always meet manufacture specifications. In addition, cam timing can be negatively impacted by tolerance stacking, and/or manufacturer's decisions to target overall performance as a goal rather than racing performance.
As already indicated, cam degreeing procedures are known, and, in fact, there are different ways to degree a camshaft, all of which provide essentially the same information. See, for example, “Essential Operations—Cam Degreeing” by Doc Fromhader in the April 1997 edition of Popular Hot Rodding. See also “How To Hot Rod Small-Block Chevy's” published by HP Books; Copyright 1976; Library of Congress #73-173702. The specific procedures are somewhat complex and need not be described here, except to note that they involve determining crank position, in degrees of rotation from top dead center (TDC), and relative to specific points on the cam shaft, e.g., the point where the cam starts to push the lifter up; where the lifter is at the lowest point of its travel; and the intake centerline. The procedure must be repeated for each lifter (intake and exhaust) for each piston. Currently, the most widely employed technique is to use a single magnetic indicator base holding a single dial indicator to record the various measurements. The base is first located on the engine block such that the dial indicator can be maneuvered into position where the indicator stem will measure the movement of a piston in the cylinder on either side of top dead center. Once top dead center (TDC) has been located, the cam degreeing procedure is commenced, moving the indicator base as necessary to record measurements for each lifter associated with each piston. It will be appreciated that the procedure is both tedious and time consuming. Moreover, the indicator base may move during measurement, or between measurements at a given location, thereby placing the accuracy of the readings into question. Thus, there remains a need for a simple, easy to use, and accurate cam degreeing device or tool which minimizes the number of adjustments and/or tool relocations.
SUMMARY OF THE INVENTION
In accordance with a first exemplary embodiment of this invention, a measurement platform tool is provided which may be temporarily secured in place within the lifter gallery and atop the engine deck of a partly assembled engine. More specifically, the platform is designed to be attached utilizing existing threaded head bolt holes already present in the engine block. Since the pattern of bolt holes is repeated in areas adjacent each cylinder, the measurement platform may be relocated to corresponding positions for each cylinder. For piston and lifter measurements at any one cylinder, however, the platform remains stationary.
The platform itself consists essentially of a relatively thick plate which may be manufactured from any of several suitable materials, with aluminum presently preferred. In addition to the three holes by which the platform is secured to the block, three additional holes are provided. One of these additional holes supports a vertical rod or standard to which a pair of dial indicators can be secured, utilizing conventional adjustable mounting hardware. The remaining two holes are sized and located to vertically align with a pair of lifter substitutes for the intake and exhaust valves associated with a respective cylinder. As explained in greater detail below, the lifter substitutes extend upwardly through the holes in the platform where they are engaged by stems of the first two dial indicators. A third dial indicator is supported on a second vertical standard welded to one of the bolts used to secure the platform to the block. This third dial indicator is used to determine TDC for the piston, and thus, the indicator stem is located to engage the top of the piston as it approaches its upward limit of movement and as it begins its downward movement.
A pair of lifter substitutes are provided which are inserted within the inlet and exhaust lifter bores. The lifter substitutes are spring loaded by a pair of coil springs interposed between the bottom of the platform and the lifter bores within the block. Small washer-like guides may be utilized to keep the springs centered on the lifter rods. The springs are sized to be under compression and to apply a downward force to the lifter substitute rods. This insures that when the cam lobes rotate to a position where the lifter rods would normally descend, the spring bias insures that they do in fact descend and do not have to be pushed downwardly manually to overcome the friction within the bore. The upper ends of the substitute lifter rods have small recesses which allow the dial indicator stems to be centered on the lifter rod substitutes.
With the above arrangement, lifter rod travel for both the inlet and the exhaust lifters as well as piston travel can be measured simultaneously without having to relocate the measurement platform for each.
A conventional degree wheel is required for use with this invention for the cam degreeing procedure, and is normally attached to the front of the crank shaft. A pointing device is also provided for attachment to the block in conventional fashion so that it can locate the degree marks on the degree wheel as the latter rotates. With this apparatus, which may be provided in kit form, cam degreeing procedures can be carried out in a quick, efficient and accurate manner heretofore not available in the prior art.
In an alternative embodiment of the invention, the mechanical dial indicators may be replaced with electronic sensors for use with an electronic degree wheel kit so that the various measurements can be displayed as digital read-outs on a control panel.
In a still further advanced version of the invention, a micro-processor may be employed in conjunction with the control panel to measure and record all readings throughout the procedure. A print-out may then be obtained which will display all of the readings and precisely pinpoint the cam degree. Alternatively, the operator could simply press a button on the control panel and the computer would post the accurate cam degree on the control panel or separate monitor screen.
In accordance with this continuation-in-part application, a modified measurement platform tool is provided for use with single or double overhead cam engines. However, it will be appreciated that this tool is also suitable for conventional non-overhead cam engines. This platform tool includes a pair of arcuate bridge components which may be mounted to existing valve cover holes at the front and back of the engine head, with a plurality (for example, three) rods extending between the two bridge components. With this arrangement, dial gauges or electronic indicators can be mounted for sliding movement along the rods extending between the bridge components. For a single overhead cam engine, one of the side rods can be employed and a pair of gauges (mechanical or electronic) can be located one behind the other on the rod (using conventional universal type brackets), directly above the axially spaced intake and exhaust lobes of the single camshaft. A third gauge for measuring piston movement may be mounted in a spark plug hole by means of a special adapter providing direct axis to the top of the piston. Alternatively, depending on the location and orientation of the spark plug holes, this third gauge may also be sup
McCall Eric S.
Nixon & Vanderhye P.C.
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