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Just recently the engine developed this mild surge while I am cruising at a constant rpm. When I start out easy it also hesitates slightly right when I start out Any suggestions?

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FWIW, my Magnum 360 crate engine surges slightly at cruising speed when I have vacuum advance connected. Tried tuning a little with it connected but found it just runs better and doesn't surge with the vac advance disconnected.

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NO: 18-08-93 Rev. A
SUBJECT: Engine Buck, Surge Or Noise - Oil Pump Drive Gear Wear
DATE: Nov. 26, 1993
THIS BULLETIN SUPERSEDES TECHNICAL SERVICE BULLETIN 18-08-93, ISSUED ON
6/18/93, WHICH SHOULD BE REMOVED FROM YOUR FILES. THIS BULLETIN ADDS
CAUTIONS TO THE PROCEDURE, WHICH ARE HIGHLIGHTED WITH **ASTERISKS** AND
PRINTED IN RED.

SYMPTOM/CONDITION:
Vehicle exhibits warm engine surging, light bucking, or cold engine lack of
power or burst spark knock. Engine noises (light knock or tapping sound at
rear of engine) may also be experienced with no driveability complaint.
These conditions may be caused by excessive oil pump drive gear wear.

DIAGNOSIS:
Remove the distributor cap and grasp the rotor and using a rotational
motion, check the total clockwise/counter-clockwise movement at the rotor
tip. If the rotor tip movement is 5.0 mm (3/16") or more, proceed with the
following repair procedure.

PARTS REQUIRED:
Quantity
Part No.
Description

1

53020546
Oil Pump Drive Gear

1

01737725
Block Bushing

REPAIR PROCEDURE:
This bulletin involves replacing the oil pump drive gear with a revised part
and the

drive gear block bushing.

1.. Remove distributor and distributor/oil pump drive gear block bushing
as outlined in the appropriate service manual.
**NOTE: TOOL NUMBER C-3052 (DISTRIBUTOR DRIVE SHAFT BUSHING PULLER) MUST
BE USED TO REMOVE DISTRIBUTOR/OIL PUMP DRIVE GEAR AND TOOL NUMBER C 3053
(DISTRIBUTOR DRIVE SHAFT BUSHING DRIVER/BURNISHER) MUST BE USED TO INSTALL
THE NEW DISTRIBUTOR/OIL PUMP DRIVE GEAR BUSHING.**

2.. Install new drive gear block bushing P/N 01737725 and revised oil pump
drive gear P/N 53020546 as outlined in the appropriate service manual.
**NOTE: THE CORRECT POSITION FOR THE DISTRIBUTOR/OIL PUMP DRIVE GEAR
BUSHlNG IS SHOWN BELOW.**(See Illustration)

3.. Change engine oil and filter.
4.. Perform the required distributor indexing procedure as outlined in the
appropriate service manual or use the alternate procedure outlined in steps
5-9.
ALTERNATE DISTRIBUTOR INDEXING PROCEDURE

5.. Connect a voltmeter to the distributor sensor connector by removing
the end seal and carefully back probing the connector. Connect the positive
lead to the sensor output pin (pin 3, either a tan wire with a yellow tracer
or a gray wire, depending on vehicle application). Connect the negative lead
to the sensor ground pin (pin 2, a black wire with a light blue tracer).
6.. Rotate the engine clockwise as viewed from the front, until the number
one mark piston Top (TDC) compression on the vibration damper should line up
with the zero degree (TDC) mark on the timing chain case cover.
7.. Continue to rotate the engine slowly clockwise until the V6 or V8 mark
(depending on engine type) lines up with the zero degree (TDC) mark on the
timing chain case cover. The V8 mark is 17.5°after TDC and the V6 mark is
147° after TDC.
NOTE: DO NOT ROTATE THE ENGINE COUNTER CLOCKWISE. IF THE ENGINE IS ROTATED
BEYOND THE MARK, RETURN TO STEP 6 AND REPEAT THE PROCEDURE.

8.. With the distributor clamp bolt loose and the ignition switch in the
ON position, rotate the distributor slightly in either direction until the
voltmeter switches between the sensor transition point of 0 and 5 volts.
9.. Adjust the distributor as close as possible to either side of this
transition point and tighten the distributor clamp bolt to 170-230 in. lbs.
(19-26 Nm).
POLICY:
Reimbursable within the provisions of the warranty.

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