Oils and Lifter Tapping

[Kevin68N71]

Pre-question gripes:  One of the irritants in the collecting car game is when the topic of oil comes up.  Oil is a very strange topic, because EVERYONE has their discrete opinion on oils, and often contradicts the very next person that speaks...you can have a roomful of people and not ONE of them will agree with anyone else on oils.  I have noticed this all my life, even back to being a kid and going in for a quart of oil and having the counter guy give me "the talk", in this case, not about sex, but about why the oil I was selecting was somehow WRONG.  Read any forum (not knocking this one, which is great!) and one guy will say the only oil to use is Amsoil, and the next guy saying Purple, and the next guy saying you need tons of zinc, the next guy saying you only need zinc if you race, and on on on on on on on.  The topic of oil is the most contradictory topic in the car world.

All that nonsense said, want to get folks opinion on the following oddity.

With all my cars (save the new ones that have small tolerances and want a OW-xx type oil) my go-to oil has ALWAYS been Castrol GTX 10-30 (or 10-40 in a pinch).  Not only is it a typical viscosity cited in owners manuals, I have had fantastic results with it all my life.  (208k in my Mustang GT, 300K in my Dad's Mercury Grand Marquis, I could go on).

The car I am discussing here is my 1971 Charger Super Bee.  It has a later 440 in it, it has always ran very well.  This past year I have tended to a lot of service issues, and decided that I should consider the zinc situation.  I researched a lot, called a number of the additive companies, and decided on the Castrol 20-50w with zinc already blended.  It made sense to me as Castrol is a great motor oil, and the idea of it being pre-blended at the source was appealing.

So my latest work was replacing the squishy, degraded motor mounts, which I think were original!  The only other things I did was change the oil with the 20-50w zinc, and put on a new Wix filter.

Starting the engine, for the first minute it was fine, then it started being noisy.  It sounded like lifter clatter.  I removed my fan belts just to double check that the alternator or PS pump weren't making noise, as the noise was coming from the front of the engine.  Nothing changed when I did that.

I took out my stethoscope and the noise certainly was coming from the front of the valve covers, both sides.  I had never had this noise on this car.  It was not a knock like a con rod.  My oil pressure gauge read fine, although obviously those can be faulty on a car this age, but it read what it has always read, pretty much needle in middle of the window.  I increased the idle speed a bit, the clacking did not becoming noisier but it was still there.  I tried several cycles, no change.  The engine was smooth and revved freely, but the noise was concerning.  It wasn't super loud, but on a worry scale of 1 to 10, I would give it a solid 6.  In other words, don't drive it.

I considered just replacing the oil pump, as it is one thing on this car I have not replaced.  But I wanted to try one more thing.  I drained out the 20/50w, removed and replaced the filter, and put in Castol 10/30w.  When I first stated the car, there was the clacking again.  About a minute later, the sound softened then completely disappeared.  I rev the car, no clacking. The 20/50w appeared not to be reaching the rockers/lifters.etc.   

So, as we know, the 10 weight would have a thinner consistency.  Viscosity definitions across the board usually read like this: 

"A thinner oil reaches the engine parts quicker, and circulates faster, while a thicker oil tends to adhere more easily to the engine parts, and will provide better lubrication when engine tolerances have deteriorated, or in severe-duty applications like racing or off-road engines. Viscosity will determine how your engine's oil will deal with changes in temperature, pressure, and speed."

Obviously, the Super Bee is not a newer style engine that requires the very thin oil because of close tolerances.  As such, I didn't even consider that bumping up the low end of the viscosity to 20W would be an issue.   So why would my engine obviously hate this?

Many questions come to mind.  Has anyone else experienced this?  Do some premixed zinc additives have this kind of effect?  Did Castrol goof and give me 50w oil??

Any thoughts on the?  Sorry for the long length of post, just wanted to paint a complete picture.

[Kevin68N71]

Another dumb thought.  Do oil pumps, as they wear, have more difficulty "throwing" thicker oils than thinner ones?  I would think that as they wear the thicker oils would be easier to grab, but now not sure.

Maybe the pump is weak....

[Kevin68N71]

I think I might have answered my own question, found these online:

The oil itself is not so much the power robber as is the oil pump and clearances which simply makes the pump work harder to move a higher viscosity oil throughout an engine. Higher or heavier viscosity oil drives up the oil pressure which in turn makes the oil pump work against a higher resistance.

[b5blue]

  The nut of this issue is THEY CHANGED THE OIL so no matter what your use to or you did it's not relevant. (See the "Sticky" about this.)    I just tore down a 440 that was starting to eat it's lifters after a total overhaul. Long ago finding this site and that Sticky saved it. (2 lifters still have bars on the face.)
  Changing to VR-1 did the trick and learning to read Zinc numbers kept it going.

[Kevin68N71]

I appreciate your answer, but the car had absolutely no ticking or noise before I changed it to 20/50.

The more I think about it, the more I am thinking that the oil pump simply is slowly wearing out, and the thicker oil was pushing it over the edge in terms of getting the oil up to the very top of the engine.

Heck, a Melling is not that much $, it is not a PITA to replace like a Chevy, I think I am going to change it.  Certainly won't hurt anything.

[b5blue]

Worth a shot.