FORM 1316 (REV. C) 06/03
INSTALLATION INSTRUCTIONS
ADJUSTABLE FLANGE DISTRIBUTOR ADJUSTMENT
PROCEDURE TYPE 482, 590, 790 AND 791 DISTRIBUTORS
GENERAL INFORMATION
Adjustable flange distributors allow you to raise or
lower the distributor by moving the flange down or up
the distributor shank so that the distributor drive gear
engages properly with the camshaft gear. Adjustment
is necessary anytime the engine block deck height is
changed, cylinder heads have been machined or
offset, or any intake manifold modifications.
FIGURE 1
mark lines up with the top dead center (TDC) mark on
the timing tab and #1 cylinder is on its compression
stroke.
NOTE: Removing the spark plugs may make it
easier to turn the crankshaft.
Step 2
Remove the distributor cap.
Types 482, 590, 790 and 791 mentioned in this
writing are derived from the particular distributor’s part
Step 3
number (example: 3448205; 3479005). Type 482’s
Loosen the flange and set screws. Slide the flange up
shallow groove on the upper shank of the distributor
the upper shank.
is the stock flange height reference for 265-454
Chevrolet engines (figure 1). Type 790’s and 791’s have
two shallow grooves. The lower shallow groove on the
FIGURE 2
upper shank of the distributor is the stock flange
height reference for Chevrolet V8 265-454 engines.
The upper groove on the upper shank of the distri-
butor is the stock flange height reference for Chevrolet
V8 Tall/Truck Block engines (figure 2).
Align the bottom of the flange with the shallow groove
and tighten the flange screw to position the flange at a
stock flange height reference. Tighten the set screws.
Step 1
Disconnect your ignition system. Turn the engine
crankshaft in the direction of rotation until the timing
TYPE 590,
TYPE 790,
AND
TYPE 791
www.mrgasket.com
MALLORY TECHNICAL SUPPORT
(775) 882-6600
1
FIGURE 3
Step 7
Put the distributor gasket in place (if one is used).
Place the distributor in the engine with the rotor
pointing in the same general direction as the original
distributor. Put the distributor hold down clamp in
place and tighten slightly.
Step 8
Turn the engine crankshaft in the direction of rotation
two full turns until the timing mark lines up (again)
with the TDC mark on the timing tab. Remove the
distributor hold down clamp and remove the distri-
butor from the engine.
FIGURE 4
Step 4
Place the distributor in the engine with the rotor
pointing in the same general direction as the original
distributor. It is not necessary to have the distributor
gasket in place at this time.
NOTE: The distributor shaft tongue must be
fully engaged into the oil pump drive. It may be
necessary to turn the oil pump drive, or turn the
engine crankshaft in the direction of rotation two
full turns until the timing mark lines up (again)
with the TDC mark on the timing tab, to allow the
distributor shaft tongue to fully engage into the oil
pump drive.
Step 5
Lift the distributor 0.010-0.030”. Slide the flange down
to rest on the intake manifold. Tighten the flange
screw. Remove the distributor from the engine.
Step 6
Coat the teeth of the distributor drive gear with gear
marking compound (White Lead; High Spot Blue™;
Prussian Blue™). Camshaft/moly lube may be used
instead of gear marking compound.
Step 9
Check the mating pattern on the distributor drive gear.
The mating pattern centerline must be within 1/16”
(0.0625”) of the gear tooth’s centerline (figure 3).
Step 10
If the mating pattern centerline is above the gear
tooth’s centerline or more than 1/16” below the gear
tooth’s centerline, loosen the flange screw, move the
flange, tighten the flange screw and repeat steps 6-9.
Step 11
Clean off the gear marking compound on the distri
butor drive gear. Tighten the set screws. Put a small
amount of RTV silicone on the bottom of the flange at
the split (figure 4) to prevent oil and vapors (blow-by)
from leaking. Proceed to the distributor instructions.
MALLORY IS A DIVISION OF THE MR. GASKET PERFORMANCE GROUP
550 MALLORY WAY, CARSON CITY, NEVADA 89701
(775) 882-6600
FAX (775) 887-4377
www.mrgasket.com
FORM 1316
(REV. C) 06/03
Made in U.S.A.
Printed in U.S.A.
2
MALLORY IGNITION
550 MALLORY WAY, CARSON CITY, NV 89701
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