360 Oil, Timing, Sparkplugs

Tech Question

Art Pesaturo, Wellington, FL, 1970 Plymouth Duster 360

I have a 1970 Plymouth Duster with the following: Theengine is a 360 with a Mopar Purple Shaft 292 duration, 0.508″ lift cam,ported and polished heads, .30″ over 10.5:1 Keith Black pistons, MoparPerformance aluminum intake manifold, Edelbrock 600cfm 4-barrel carb, MSDelectronic ignition, lightened flywheel, ceramic coated Thorley headers, anddual FlowMaster exhaust. 350 plus horsepower. Runs on 93 octane pump gas.Has a 4-speed manual transmission and 3.91 SureGrip positraction rearend.

Living in southern Florida and given the above what weight oil should Iuse?

Also, what kind a spark plugs and what gap? Lastly, what degree should thetiming be set above or below TDC?

Your input would be greatly appreciated.

Art, if the engine bearing clearances are all stock, i.e., tight, I’d gowith synthetic 10W30 or mineral 15W40. If the oil pressure drops below 15PSI at 1,000 RPM, then go heavier — say, 20W50.

My personal recommendation on plugs: Bosch Platinum 4218, gapped at 0.035″

The timing’s a bit trickier. Hold the revs at 3,000 RPM, with vacuum advancehose removed. Set timing to 33 deg BTDC. This should result in about 15 deg.BTDC at idle. If it’s not between 10 and 20, the distributor advancemechanism needs to be reworked. It should not begin to advance until atleast 200 RPM over idle speed, whatever that may be, or the idle will beunstable.

Next, while held at 3,000 RPM / 33 degrees, temporarily connect the vacuumcannister to manifold vacuum. Timing should advance at LEAST 10-12 moredegrees. If less, stop “notch” on vacuum cannister arm must be modified.

Now, while at curb idle, reconnect the vacuum cannister to ported vacuum.There should be no change in spark advance or idle RPM. If there is, thecarb needs to be reworked.

By the way, I really hope that .30″ overbore is a typo! And, please, dropthat Chebby rear end nomenclature!


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