4/1/2003
Click on a thumbnail to see the full-size image
Improving engine balance on 1992-’93 GM 6.2L VIN C and J diesel truck engines.
Engine Builders: The AERA Technical Committee has issued the following information on improving engine balance on 1992-’93 GM 6.2L VIN C and J diesel truck engines.
While some owners of these engines have accepted the original driveability condition as normal, others have complained of "rough running" and have looked for methods of improving that condition. AERA members report that GM 6.5L diesel engines may be rebalanced to produce smoother operation by adding heavy metal to each end of the crankshaft.
When the engine rotating weight is rebalanced using 50 percent of the reciprocating weight and 100 percent of the rotating weight, members report that customers have been unexpectedly pleased by the results. Some AERA machine shops rebalance all 6.5L engines to improve driveability and performance.
Engine Builders: Updates by Subaru to its service manual has made AERA Tech Bulletin TB1945 obsolete. The information within this bulletin gives the correct method of installing cylinder heads on the 1996-2001 Subaru 2.5L VIN 6 engines. These engines were used in the Forester and Legacy vehicles.
To help reduce the likelihood of cylinder head warpage during head removal allow the engine to first cool and then loosen the cylinder head bolts in the sequence shown in Figure 1, at the top (below left).
To assure an effective cylinder head gasket seal, use the method listed below while observing the alphabetical torque sequence shown in Figure 1, bottom.
Cylinder Head Installation
- Apply a coat of engine oil to washers and bolt threads.
- Tighten all bolts in sequence as shown in Figure 1 bottom to 22 ft.lb (29 Nm or 3.0 kg-m).
- Then, tighten all bolts in sequence to 51 ft.lb (69 Nm or 7.0 kg-m).
- Back off all bolts by 180° in sequence first; and then back them off by 180° again.
- Tighten bolts 1 & 2 to 25 ft.lb (34 Nm or 3.5 kg-m).
- Tighten bolts (3), (4), (5) and (6) to 11 ft.lb (15 Nm or 1.5 kg-m).
- Tighten all bolts an additional 80-90°in sequence.
- CAUTION: Do not tighten bolts more than 90° at this time.
- Further tighten all bolts by 80-90°in sequence again.
- CAUTION: Ensure that the total "re-tightening angle" [in steps 7 and 9] do not exceed a total of 180° rotation.
Engine Builders: According to the AERA Technical Committee, the crankshaft used in 2001-2003 Ford 3.8L VIN 4 engines is significantly different than previous year’s engines. Installing a previous year crankshaft in this newer engine will cause severe engine vibrations. Pay attention to the following information if you work on these engines.
Crankshafts for the 2001 and newer engines have six counterweights while previous year crankshafts have only two as shown in Figure 2, above. The balance of the two crankshafts is entirely different.
The 2001 and newer crankshaft can be identified by the casting number 1F2E.
Installing a previous year crankshaft in this latest version of this engine will produce an unacceptable engine vibration. Verify the crankshaft-casting number before obtaining a replacement crankshaft for this engine.