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Engine Builders: The AERA Technical Committee offers the following information regarding a revised timing cover for 2004-2005 Mack E-TechTM 12.0L diesel engines. This revision was made to strengthen the power steering pump mounting flange to help reduce breakage and cracking on certain applications.

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To provide strength, additional metal was added to the power steering pump mounting area of the timing gear cover. This was done particularly for engines used in vehicles equipped with the heavier Vickers model V20 power steering pump. The additional material was added to the power steering pump mounting flange on both the inside and outside of the cover. With this change, the timing gear cover part number has been changed to p/n 333GB5131BM.

Part Number: 333GB5131BM

Description: Timing gear cover with strengthened power steering pump mounting flange, ASET™ AC, AI/AMI and E-Tech™ engines.

Replaces: p/n 333GB5131AM

The most noticeable feature of this new timing gear cover is the three strengthening ribs located at the bottom of the pump-mounting flange as shown in Figure 1.


This revised timing gear cover was implemented into production early November 2004 for ASET™ AI/AMI engines and early December 2004 for ASET™ AC engines. The timing gear cover is also available through the Mack Parts System as a replacement for any existing cover that has cracked in the area of the power steering pump mounting flange on ASET™ and E-Tech™ engines.

Engine Builders: The AERA Technical Committee offers the following information concerning refinishing cylinder bores for oversize pistons on 1999-2005 GM 5.3L VIN T engines. Currently, oversize pistons are available in .020? (.50 mm), .030″(.75 mm) and .040″(1.00 mm), which allows for refinishing a damaged or worn cylinder bore. The original cylinder bore size is a diameter of 3.7795-3.7802″(95.999-96.017 mm).


If it’s determined a larger oversize bore may be required to repair a particular block, an alternative should be considered. The 5.3L cylinder block has very thick cylinder walls, which is uncharacteristic of modern lightweight engines. It has been determined by ultrasonic testing that sufficient wall thickness exists to allow an overbore size of the LS1/LS6 GM engines. The bore size for those engines is 3.8970-3.8980″(98.984-99.009 mm), which is an increase of .120″(3.00 mm).

One engine builder reports that a standard bore cylinder wall thickness, measured at the major and minor thrust sides (intake to exhaust sides), are a healthy .450″thick. The cylinder wall thickness measured front to rear on the block was approximately .300″(7.620 mm) thick.


A third option of repair would be to install cylinder sleeves in damaged bores. The bores could then be bored either back to the standard bore or appropriate oversize piston diameter.

For information on receiving all of AERA’s regular monthly technical bulletins and other association services and benefits, call toll free 888-326-2372 or send an e-mail to [email protected] AERA’s Web site is

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