| MAIN BEARING KNOCK |
Main Bearing Knock On
GM 3.3 & 3.8L (Buick 3300 & 3800) Engines
AERA members report knocking noises coming from the front of GM 3300 & 3800 Buick engines. The noise is most noticeable when the engine has reached operating temperature. One possible cause for this knocking noise may be from excessive oil clearance at the front main bearing location.
Diagnosing excessive main bearing clearance is easily done by removing the accessory drive belt from the engine after it has reached operating temperature. If the noise diminishes when the engine is started again, front main bearing clearance may be more than .0012 (.030mm). The clearance may be reduced by installing .001 (.025 mm) undersize main bearings. GM permits the use of only one bearing shell half in the cap, but warns not to reduce
clearance below .0008 (.020 mm).
GM specifies the main bearing clearance as .0008-.0022 (.020- .055 mm). AERA suggests machining the crankshaft main bearing journals and the main bearing housing bore so that the minimum allowable clearance is maintained, avoiding the possibility of main bearing knock.
The AERA Technical Committee |
| HARMONIC BALANCER BOLT |
Problem On Replacing Harmonic Balancer Bolt On Some
Buick Built 3.8L (231 CID) V6 Engines
When the crankshaft in the subject engine is replaced, the original harmonic balancer bolt may not fit the crankshaft.
Some replacement crankshafts have been drilled and tapped for a 3/4 - 16 bolt instead of the original 5/8 - 18 bolt.
The OEM replacement bolt (3/4 - 16) and washer are:
Bolt No. 271629
Washer No. 1199944
The AERA Technical Committee |
| ENGINE VIBRATION & FLYWHEEL MOUNTING PROCEDURE |
Engine Vibration And Flywheel Mounting Procedure
On Buick 6.6L & 7.0L (401 & 425 CID) Engines
Buick 6.6L and 7.0L (401 & 425 CID) engines are balanced to very close limits. The replacement of any part within the engine or drive line can result in a vibration condition. In replacing the engine or crankshaft the following instructions should be followed.
1. Mark drive shaft before disconnecting so that installation can be in original position.
2. If automatic transmission unit, mark position of converter to flex plate.
3. Remove engine. Check all motor mounts and replace if broken or damaged.
4. Install engine. Use extreme care to see that flywheel, or flex plate bolted to converter are installed in original position.
5. Align flex plate or flywheel to crankshaft, aligning hole in crankshaft flange. See (A)
Following the above procedure, if a vibration is experienced, it will then be necessary to purchase balance weight part #1178109 from a Buick dealer and install it under head of two converter pump bolts, then start engine to check vibration. The weight may have to be rotated to a different location until vibration is corrected. Use tachometer and note critical speeds.
Balancing should be included in the labor charge of installing
the engine or crankshaft.
(insert illustrations)
Align hole (A) in crankshaft flange to (B) alignment hole in flywheel or converter drive plate. Converter drain plug (C) must be installed in notch (D) in drive plate to allow removal of drain plug.
The AERA Technical Committee
##END## |
| VALVE TRAIN NOISE ON V6 ENGINES |
Valve Train Noise In 1978-84 Buick V6 Engines
180 (3.0L), 231 (3.8L) & 252 (4.1L) CIDS
Valve train noise is a common complaint on the Buick built V6 engines after rebuilding the heads, the short block or complete engine. The noise is almost always attributed to inadequate lifter preload. Checking the valve tip to rocker arm tip clearance and insuring proper lifter preload will eliminate this
problem.
Inadequate lifter preload is compounded by replacing the stock steel shim type head gaskets with thicker composition type head gaskets. The difference in thickness is only about .015, but when combined with the rocker arm ratio of 1.55, nearly .025 of lifter preload is lost by making this change.
In addition, some members report that they are finding pushrods of varying length (standard, plus .030 and plus .060) in these engines. It is recommended that AERA members check and sort these pushrods according to length.
The correct lifter preload for these engines is .080 to .180. By using pushrods of varying lengths these figures are achievable. Some members report using the intake pushrod for 348-409 CID Chevrolet engines as a standard practice on the Buick built V6. This pushrod is about .060 longer than the standard length Buick V6 pushrod. The AERA Technical Committee recommends checking valve lash on each valve and selectively fitting each with the correct length pushrod to give adequate lifter preload.
The AERA Technical Committee |
| PISTON KNOCK ON V6 ENGINES |
Piston Knock In
Some 1978 Buick Built V6 Engines
It has been reported that some Buick built V6 engines, which may be found also in vehicles of other GM divisions, may have a faint knocking noise particularly during warm up. The noise may be caused by the number 6 piston contacting the counterweight on the crankshaft.
A scuff mark on the skirt of the number 6 piston indicatesk the piston has been striking the crankshaft counterweight. To correct the problem, it is recommended that .010 be carefully filed or ground off the area of the scuffk mark.
The AERA Technical Committee |
| DETERMINING CORRECT CAMSHAFT - ODD & EVEN FIRE ENG |
Please Destroy Original TB 241 Dated Jan., 1982
Determining The Correct Camshaft On
1975-77 GM (Buick) Odd And Even Firing 3.8L (231 CID) Engines
Members are cautioned that there are two different types of
camshafts for the odd firing General Motors (Buick) 3.8L (231
CID) engine:
Type 1 has a non-integral distributor drive gear, a
removable drive gear on the end of the camshaft.
Type 2 has an integral distributor drive gear on the end of
the camshaft, permanently attached.
To identify an even or odd firing engine, check the V.I.N.
number. The fifth digit from the left denotes the type. A
letter C indicates an ODD firing engine. All other codes
indicate an even firing engine.
1975 through early 1977 General Motors (Buick) 3.8L (231 CID)
engines used odd firing. Later in 1977, even firing engines were
used.
The AERA Technical Committee
April 1982 - TB 241
##END## |
| V6 TIMING CHAIN NOISE |
Timing Chain Noise On Some General Motors (Buick-Built) 1975-78 Engines
Timing chain noise has been experienced on some of the subject engines. This can occur on 1975-77 odd-firing and some 1978 even-firing V6 engines. The noise is a result of the timing chain damper spring hitting the inside of the timing cover.
After removing the timing cover, check for a worn or shiny spot inside the timing cover in the area of the damper spring pilot. If this condition is found, provide additional clearance by carefully grinding at the worn spot, but be careful not to
machine through the timing cover casting.
The AERA Technical Committee |
| VALVE CROSSHEAD CLEARANCE |
Valve Crosshead To Rocker Lever Clearance On
NH, NT & V-1710 Series Cummins Engines
Valve crosshead nose to rocker lever clearance on the subject engines must be checked during engine rebuild and at any time valve crossheads are replaced on engines using crossheads No. 123416 & 3000326. A minimum of .020 (.51 mm) clearance must be present as illustrated in Fig. 1, on the cylinder being checked with valves completely closed and crosshead in the upmost position. After installing rocker lever assemblies, check crosshead to rocker lever clearance as follows:
1. Turn crankshaft slowly in direction of rotation until the valves are closed on the cylinder being checked. With rocker lever held firmly against the stellite pad of the crosshead, a .020 (.51 mm) wire type feeler gauge must pass between the crosshead nose and the lower beam section of the rocker lever.
2. If the feeler gauge does not pass through:
a. Remove the rocker lever and/or crosshead and grind the nose of the crosshead or rocker lever beam in the area circled in Fig. 1 until enough clearance is obtained.
b. If the rocker is ground, grinding should cover the complete area illustrated in Fig. 2 in a continuous arc. Do NOT grind just the contact area.
Caution: A sharp depression in this area will cause a stress riser and eventual failure of the lever. Grind only enough material to achieve the required clearance. If grinding enters the oil passage, the rocker lever must be junked.
c. Grind sharp edges smooth.
The AERA Technical Committee |
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| CRANKSHAFTS INDUSTRIAL |
Crankshafts Used In Industrial Applications On
GM (Chevrolet) 5.7L (350 CID) Engines
When the GM (Chevrolet) 5.7L (350 CID) industrial engine is used in some applications such as lift trucks, the only crankshaft that is applicable has the forging number 1182. Dimension A of the rear flange is slightly smaller than that of other crankshafts used in General Motors 5.7L (350 CID) engines.
The larger flange crankshafts will not pass through the center hole of the bell housing. This is very critical when an oil clutch system is used.
The AERA Technical Committee |
