After 1/2 hour of driving or so, when the motor is fully warmed up, the oil light flickers off and on at idle. There is a tapping sound when this happens.

Putting the car in neutral gets rid of the problem, and the light does not come on during driving.

The motor does not smoke, but it is original so I am sure the bearings are worn or something to that extent.

Would a heavier weight of a high mileage oil help this problem? Or is there an additive l can put in like Lucas?

PUT IN A NEW OIL PUMP

Why are you looking for a TEMPORARY fix?
What weight of motor oil are you using in it now?

Yes a heavier weight of oil will help.

That is the sure sign the engine is worn. The bearing clearance is big now,and the oil pump bypass spring is soft, lowering oil pressure. The pump gears are probably worn out, too.

Additives might help, as will heavier oil, but in a few hundred miles, this will start again. l guess drive it until it dies, and start shopping for a new engine. The 318 is nearly bullet proof, but these bullets are being fired from the inside!

whenever that happened to me, l was low on oil

First check how much oil you have, this can happen when the level is low. Second check the pump it may be warn out. And last if it is neither of those you need to get the motor rebuilt. The additives will do little as would a different oil, those would be very short term fixes. Good Luck.

If you follow billo is advice, you might as well put some new bearings in as most of that job is done just getting to the pump.

Replace with ''ones'' or ''twos'' over size and micrometer the rod journals. If they are round the mains will be OK for the most part.

Chrysler parts for the 318 are really cheap.

try cleaning the pick up sump out for the oil pump and see if that helps it,when they get stopped up they,ll do this once they get warmed up,you can also replace the oil pump while your at it and that may fix it,or you may need to do a lower end rebuild on it there no real quick fix for it though,good luck.

Well, what typically happens to most mopar engines from that era is, the cam timing gear is aluminum, & the teeth r coated with nylon. After many years of faithful service the nylon begins to break off, & fall into the oil pan. They then migrate to the pumps pickup screen, slowly restricting the flow. Without good oil flow, bearings begin to starve for lubrication, accelerating wear.
Anyway, its time to pull the pan & look. At the VERY minimum, rod bearings, oil pump & timing chain set will buy u some time, but a full rebuild is in ur future.
BTW bitchin car, good luck~Dan

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