Usage:
All Caterpillar Engines with Keystone Piston Ring Grooves
- SUPPLEMENT: 03/02/87
SERVICE MAGAZINE; JUNE 16, 1986; PAGE 2; "Increase Piston Reuse With Keystone Piston Ring Gauge Group." Because of a tighter second land on 7W3668, 7C473, and 7C3496 Pistons, no gauge exists to correctly measure and determine reusability of these pistons. Until a new gauge is available, reuse these pistons only if a 0.38 mm (.015") feeler gauge can slip easily between 8T3149 "F" Gauge Assembly and the land between the top two piston rings.
Disregard an earlier Supplement on this same subject that appeared in Service Magazine; August 4, 1986; Page 7.
--------------- END SUPPLEMENT ---------------
This article replaces similar information in Service Magazine, September 23, 1985, Page 2, "New Keystone Ring Groove Gauge Available"; Service Magazine, May 10, 1982, Page 10, "5P4812 Gauge Group Components Available Separately"; Guideline For Reusable Parts-Pistons, SEBF8049, Pages 38 and 39.
During engine reconditioning or repair, any pistons removed should be cleaned and checked for reusability as described in the Guidelines for Reusable Parts - Pistons SEBF8049. Pistons with Keystone ring grooves should be checked with the new 8T3150 Keystone Piston Ring Gauge Group. The new 8T3150 Ring Gauge Group replaces the former 5P4812 Gauge Group.
Caterpillar recommends that use of the 5P4812 Gauge Group be discontinued. Some maximum limits of piston ring groove wear have recently increased. The 8T3150 Gauge Group allows for these new limits but the former 5P4812 Gauge Group does not conform to these new reusability specifications. Also, the new gauge group is more resistant to wear than the former group. The new gauge group contains additional sizes to measure piston ring grooves that the 5P4812 Gauge Group cannot measure (see gauge group application chart).
Engine coverage of the individual gauges of the 8T3150 Gauge Group is listed below and on the SEES5678 Instruction Card.
A slight amount of wear on a gauge will cause an incorrect measurement and may cause rejection of some reusable pistons. Wear on a gauge is extremely difficult to measure. It is recommended an extra new gauge group be kept as a master set. A procedure should then be established to periodically compare measurements of all gauges in use to the master set. A gauge is worn out and should be discarded if it shows a piston as not reusable and the master gauge shows the piston ring groove as reusable.
NOTE: As a Keystone piston ring gauge group wears, fewer and fewer pistons will measure reusable.
Correct usage of this type of tool can be found in Service Magazine, June 1, 1981, Page 4, "Correct Usage Of Keystone Ring Groove Gauges" and Service Training videotapes, "Use of Piston Ring Groove Gauges", 3/4" U-matic Form SEVV9164 and 1/2" VHS SEVV8164.