Spark plug gap. 1972 Cutlass Supreme 350 4bbl. Stock
April 8th, 2020, 09:59 AM
#1
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Spark plug gap. 1972 Cutlass Supreme 350 4bbl. Stock
What is supposed to be the correct spark plug gap for a 72 Olds Rocket 350 4 bbl. And what type of spark plugs you guys running. I hear two different stories on gap. .030 or .040? Please advise. Thanks
Also running a Pertronix ignition
Also running a Pertronix ignition
Last edited by Neuby7297; April 8th, 2020 at 10:23 AM. Reason: Ignition type
April 8th, 2020, 10:53 AM
#3
Running On Empty
Join Date: Jul 2018
Location: Earth
Posts: 18,103
Agree w/ the above 0.040 - that should get the engine running fine until you perform the full tune-up at which time the gap may change as you set the dwell. Ensure you perform the tune-up in this exact order.
Assuming you have the stock OEM distributor & stock OEM contact points.
With the plugs gapped to 0.040:
(1) Set/Establish Dwell Angle to 30°;
(2) Set the timing to ~10° to 12° TDC (you must disconnect the vacuum hose at the distributor and plug the hose). If the air cleaner is removed, plug the vacuum hose fitting with some tape; and,
(3) Set the vacuum (via both carburetor A/F mixture screws) to the highest vacuum you can achieve (generally ~17" Hg).
Page 6C-11 of the1970 1971 (edit) CSM. The tune-up parameters should be located on C.C.S. tag located on the fan shroud.
Assuming you have the stock OEM distributor & stock OEM contact points.
With the plugs gapped to 0.040:
(1) Set/Establish Dwell Angle to 30°;
(2) Set the timing to ~10° to 12° TDC (you must disconnect the vacuum hose at the distributor and plug the hose). If the air cleaner is removed, plug the vacuum hose fitting with some tape; and,
(3) Set the vacuum (via both carburetor A/F mixture screws) to the highest vacuum you can achieve (generally ~17" Hg).
Page 6C-11 of the
Last edited by Vintage Chief; April 8th, 2020 at 01:08 PM.
April 8th, 2020, 11:16 AM
#4
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Join Date: Jun 2009
Location: Palm Bay, FL
Posts: 4,249
Agree w/ the above 0.040 - that should get the engine running fine until you perform the full tune-up at which time the gap may change as you set the dwell. Ensure you perform the tune-up in this exact order.
Assuming you have the stock OEM distributor & stock OEM contact points.
With the plugs gapped to 0.040:
(1) Set/Establish Dwell Angle to 30°;
(2) Set the timing to ~10° to 12° TDC @1100RPM(you must disconnect the vacuum hose at the distributor and plug the hose). If the air cleaner is removed, plug the vacuum hose fitting with some tape; and,
(3) Set the vacuum (via both carburetor A/F mixture screws) to the highest vacuum you can achieve (generally ~17" Hg).
Page 6C-11 of the 1970 CSM. The tune-up parameters should be located on C.C.S. tag located on the fan shroud.
Assuming you have the stock OEM distributor & stock OEM contact points.
With the plugs gapped to 0.040:
(1) Set/Establish Dwell Angle to 30°;
(2) Set the timing to ~10° to 12° TDC @1100RPM(you must disconnect the vacuum hose at the distributor and plug the hose). If the air cleaner is removed, plug the vacuum hose fitting with some tape; and,
(3) Set the vacuum (via both carburetor A/F mixture screws) to the highest vacuum you can achieve (generally ~17" Hg).
Page 6C-11 of the 1970 CSM. The tune-up parameters should be located on C.C.S. tag located on the fan shroud.
April 8th, 2020, 12:24 PM
#5
Running On Empty
Join Date: Jul 2018
Location: Earth
Posts: 18,103
That's correct. And, that information can be obtained via the CSM or the fan shroud tag. Additionally, this can very w/ or w/o AC.
April 8th, 2020, 12:37 PM
#6
Old(s) Fart
Join Date: Mar 2007
Location: Northern VA
Posts: 47,352
Since the OP has a 1972 Cutlass, why don't we use the 1972 Chassis Service Manual? Big difference between a high compression 1970 motor and a low compression 1972 motor.
The first question is, WHICH 350 4bbl? The specs for an AT motor are different from those for an MT motor. I'll assume this is an AT car.
ALL 1972 spark plugs get an 0.040" gap. There is no fuzz on this. The Pertronix is irrelevant. Correct plug type is R46S (the MT cars used R45S).
Initial timing is 12 deg at 1100 RPM.
Slow idle speed is 600 RPM in DRIVE. Fast idle speed is 1100 RPM in PARK.
All of this info is on the tune up label on the radiator top panel.
The first question is, WHICH 350 4bbl? The specs for an AT motor are different from those for an MT motor. I'll assume this is an AT car.
ALL 1972 spark plugs get an 0.040" gap. There is no fuzz on this. The Pertronix is irrelevant. Correct plug type is R46S (the MT cars used R45S).
Initial timing is 12 deg at 1100 RPM.
Slow idle speed is 600 RPM in DRIVE. Fast idle speed is 1100 RPM in PARK.
All of this info is on the tune up label on the radiator top panel.
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