The Sunnen P-310 Valve Guide Gage Set is a hand-held comparator-type gage designed for measuring the clearance between valve stems and guides. It is capable of gaging reamed, honed, knurled, or bronze insert guides. The set includes the P-300 Gage, three probes (P-312, P-344, P-375), a P-610 Setting Fixture, a P-650 Metal Storage Case, and an instruction manual.
Function Description:
The P-300 Gage utilizes interchangeable probes to measure the internal diameter of valve guides. The gage's dial indicator displays readings in .0002" (0.005 mm) increments, showing measurements over or under a set diameter. Each numeral on the dial represents .001" (0.05 mm), with a total range of .015" (0.37 mm). The gaging points on the probes are designed to be long enough to bridge grooves in knurled guides, ensuring accurate measurements across all guide types. The gage body incorporates a probe adapter for secure seating and holding of the probe. An adjustment screw, operated with a 1/8" (3 mm) hex wrench, is used to "zero" the gage during the setting process. A retracting lever allows the user to reduce the gaging point diameter for easy insertion into the setting fixture or valve guide, and for making readings at various points along the guide. The T-handle provides a comfortable grip for holding and balancing the gage during measurements, while a supporting foot offers an additional rest point. A probe locking screw securely holds the probe in place and is loosened or tightened with the 1/8" (3 mm) hex wrench. The gage features pivot bearings with a self-locating design to ensure repeatability in readings.
Important Technical Specifications:
- P-300 Gage: Hand-held comparator-type gage.
- Dial Indicator: Reads in .0002" (0.005 mm) increments. Each numeral marks .001" (0.05 mm). Total range: .015" (0.37 mm).
- Probes (Included in P-310 Set):
- P-312 Probe: 5/16" (7.9 mm) diameter, range .300 to .340 inches (7.62 to 8.64 mm).
- P-344 Probe: 11/32" (8.7 mm) diameter, range .332 to .372 inches (8.43 to 9.45 mm).
- P-375 Probe: 3/8" (9.5 mm) diameter, range .363 to .403 inches (9.22 to 10.24 mm).
- Additional Available Probes (Not included in P-310 Set, but compatible):
- P-250 Probe (1/4"): .238 to .278 inches (6.05 to 7.06 mm).
- P-281 Probe (9/32"): .269 to .309 inches (6.83 to 7.85 mm).
- P-406 Probe (13/32"): .394 to .434 inches (10.01 to 11.02 mm).
- P-438 Probe (7/16"): .426 to .466 inches (10.82 to 11.84 mm).
- P-469 Probe (15/32"): .457 to .497 inches (11.61 to 12.62 mm).
- P-500 Probe (1/2"): .488 to .528 inches (12.40 to 13.41 mm).
- Wrenches:
- 1/8" (3 mm) Hex Wrench with Knurled Knob (Item 9): Used for locking probe and adjusting gage.
- .050" (1.25 mm) Hex Key Wrench (Item 10): Used for servicing the retracting lever.
- 5/64" (2 mm) Hex Key Wrench (Item 4 on probe diagram): Used for servicing the probe.
Usage Features:
- Probe Assembly: Probes are easily assembled to the gage body by backing out the probe locking screw, installing the probe head with the flat toward the retracting lever and countersink toward the T-handle, and then tightening the locking screw. The adjustment screw is rotated counterclockwise to retract gaging points before storage.
- Setting Fixture Use: Two valves with identical stem diameters are selected for the setting fixture. Valve stems and blocks must be clean. Valves are placed between the blocks, and the thumb screw is tightened with fingers (then backed off 1/8 to 1/4 turn to prevent distortion). The eccentric is turned to its lowest position.
- Gage Setting: The probe is inserted between the blocks in the setting fixture, resting in the "V" of the eccentric with the gage dial up. The gage is set to approximately "0" using the 1/8" hex wrench. The eccentric is then turned until the indicator reaches the largest plus (+) reading. The probe is rotated slightly until the indicator reaches the largest minus (-) reading (depressing the retracting lever may be necessary to reset). Finally, the gage is set to "0" with the wrench, and the probe is rotated slightly to confirm the needle returns to "0". Fine adjustments should only be made with the wrench, not by moving the dial face.
- Measuring Valve Guides: Before gaging, valve guides must be clean of chips and abrasive material. The retracting lever is pressed with the thumb to insert the probe into the guide, then released. For accurate gaging, the gaging points should not extend beyond either end of the valve guide bore. If the probe comes out of the bore, the retracting lever must be pressed to reposition the points inside. Readings can be taken at various points along the guide. When changing probe position or inserting/removing the probe, the retracting lever must be depressed to avoid damage to gaging points. A plus (+) reading indicates clearance, while a minus (-) reading indicates interference. The largest plus (+) reading at any specific spot is obtained by moving the gage up and down from left to right. The dial indicator needle is limited to approximately 1-1/4 revolutions. It is important not to touch the retracting lever while gaging to prevent reading errors.
- Clearance Interpretation: Any area of the guide exceeding the desired clearance (indicated by a plus (+) reading) suggests a need for correction. Recommended clearances vary by engine manufacturer and engine type, with intake and exhaust guides potentially requiring different clearances. Users should consult the manufacturer's recommendations.
Maintenance Features:
- Probe Maintenance: If the gaging action becomes sluggish or the gaging points stick open, the probe can be disassembled for cleaning. This involves loosening the set screw with the 5/64" (2 mm) hex key wrench and removing the head. The wedge is then carefully removed from the tube, ensuring the spring is not lost. The tube is flushed with an oily solvent, and point movement is checked with the wedge. The wedge is relubricated with 5-10 SAE machine oil, and the probe is reassembled, ensuring the screw engages the countersink in the tube. Wedge movement should be checked to confirm the spring pushes the wedge out to release all pressure on the gaging points.
- Retracting Lever Maintenance: If the retracting lever operates sluggishly, it can be removed for cleaning. The .050" (1.25 mm) hex key wrench is inserted into the small hole in the lever and loosened approximately one turn. The wrench is then removed and used to push the shaft out of the body. A small spring, nested in sockets in both the lever and the body, provides gaging force and must not be lost during disassembly. The indicator should be checked by pressing the anvil; if the needle moves freely and returns to its original position, it is functioning correctly. The lever and shaft should be wiped clean (not dipped in solvents to avoid washing grit into the adjustment screw). The brass pivot bearings can be cleaned, but care must be taken not to scratch or mar them, and spring clips on the bearings should not be removed. For reassembly, the spring is placed in the socket in the lever and held in place. The lever is inserted into the body, ensuring the spring is in the socket in the body. The hole in the lever is aligned with the pivot bearings, the shaft is inserted and centered, and the set screw in the lever is retightened. Finally, the lever is depressed to confirm the indicator needle moves freely and returns to its original position.
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