VCCA Home Forums TECHNICAL - 1945 AND NEWER 1949-1954 Oil for 235 engine

My engine has been completely rebuilt. Bored .030, new pistons,rings,rods, bearings,cam,hydraulic lifters. I used Royal Purple break in oil and it is time to change. What do I use? I know there are lots of opinions , but I would like a few.
I have always used Shell Rotella Diesel in my Corvairs because it has zinc additive. I assume this is true for this engine. I have the zinc additive to use if necessary.

Bill Pierson

All good 10W.30 oils have enough zinc for a "broken in " 235 engine. Additives are not necessary and too much zinc is not good also.

I disagree. Modern oil zinc content continues to decline, and it matters. I also understand that the diesel oil is not highly recommended for the old engines, because the detergent setup is entirely different than for gasoline engines. This is a huge, huge topic - and I suggest you do some research both on chat and elsewhere on the internet. There is much to learn. Any of my flat tappet engines will have zinc additives added. But as Gene says, too much zinc is also not good.

All present 10W-30 oils have 800 PPM of zinc. That is required by the Oil Institute to get a SN rating for the oil. Also the oil will contain Moly and Sulphur for amti-wear protection. At its peak most oils had 1200 PPM of zinc. The lifter to cam load is very light on 215/235 engines and they never wore off cam lobes with oils with NO Zinc.
From 1957 and up new GM cars came with a break-in oil that contained Zinc for proper lubrication of the cam lobes during break-in because V-8 engines of all makes were loosing cam lobes. At that time good oils contained almost no additives for cam protection.
The zinc does actually NOTHING in the oil under normal conditions. It only "works" when the oil film breaks down and the heat created causes the zinc in the oil to melt and stick to the metal to provide a temporary protective surface coating.The exposed camshaft in a straight six is right next to the crankshaft and gets plenty of oil thrown on to the cam when the engine is running. If you start a cold engine the zinc does nothing.

I've been using Lucas SAE 10W-30 (non-synthetic) in my newly rebuilt 194. Lucas's rated zinc value for this oil is 861 PPM.

That oil is one thousand times better than what was available in 1929.......and they never had a cam wear problen in 1929.

The cam/lifter wear problem came several years back when camshafts were being made in China and were not properly hardened. Then they blamed it on the oil.

Gene,
I sent you a PM.
Thanks

I guess I don't understand. My '40 216 original cam has 412,000 miles on it and is still within a smidgen of original specs as of rebuild last year. I have ran all weights and brands over the 55 years with very little if any wear on the lobes. So, I guess I have to agree with Gene.

This camshaft wearing lobes came from replacement cams not properly hardened and the makers blaming it on the oil.
In all my years in Chevrolrt parts and later years in restoration I have never seen a 6 Cyl chevrolet loose a cam lobe.

This is not true for V-8 engines.....but there is enough Zinc in todays good oils to protect a cam properly made with the exception being some super high lift cam and extra strong valve springs.