Moises noises.

[David Morris]

Hi All,

We are straying away for the original topic, but it's very interesting. What engine oil to use probably gets every owner to express their preference of brand and rating. Keith has said previously that 'The lubrication properties of modern oils are much better than they were 70 years ago and the thinning additives gets the oil where it is needed when cold'. This is very true, but I think there needs to be caution, before pouring in the latest oil on the shelves.

In the development of modern oils, some of the original additives have been discarded and those might just be essential to our engines. I am thinking here about our flat-topped tappets and camshaft lobes that apparently need engine oils containing plenty of zinc and phosphorus. Googling oils for flat top tappets brings up a recommendation from the author for seven different oils. One specifically is Shell Rotella Diesel synthetic 15W-40. By the way, if you watch Derek of Vice Grip Garage on YouTube, ( my go-to video channel prior to sleeping! ), he always uses Diesel oils for the older American petrol engines, for the specific reason of their old flat-top tappets.

I expect someone will be able to name the oil specificaton number on the side of the container that means that the oil in question contains Zinc and Phosphorus. I should know it, but cannot recall it at the moment?

All the best,

David

[Nick Webster]

As far as I am aware, the Rotella name is withdrawn from the UK market, but for some reason the Americans were allowed to keep it. The equivalent in UK is called Rimula, but I suspect Rimula is not a directly comparable oil. While it may be possible to find certain oils that might suit regarding technical aspects, one should also think of whether it is practical. Unfortunately synthetic oils are very expensive. I am pretty sure most Jowett owners would say they're get through quite a lot, either dropped on the garage floor or burned out the exhaust. I have owned modern cars using synthetic oils that did not use a drop between 12k oil changes but can't say my Javelin is as cheap to run as that.

Nick

[David Morris]

Hi All,

A little bit more information on zinc and phosphorus in engine oils, which are essential for flat-topped tappets. Apparently, these additives,known as ZDDP additives, adversely affect catalitic converters, so have been phased out of modern motor oils.

Personally, I use Rock Oil 20W-50 for Classic engines, cheap enough for our engines that, as has been said before, get through oil as though it's a box of chocolates!

All the best,

David

[Keith Clements]

If you want zddp in your oil just google. There are many available. I am not convinced it is required as I do not see the difference in lubrication requirements of flat top tappets.
That said I use molybdenum disulphide in engine and gearbox as it gives some dry lubrication.

Scott and I have done some research on tappets and think that although the Jowett tappets maybe flat they are offset on the cam, so there should be rotational force on the follower so providing a lubricating film.

Anyhow refer to this and other articles. https://www.duckhams.com/zddp-what-does-it-all-mean/

[Srenner]

I had valve train noise that eventually led me to removing the lifters (tappets or cam followers) and camshaft after 8k miles of use. Some of the lobes had lost material and the bottoms of 6 lifters were concave. Oil pressure was always quite good, the camshaft and lifters were new and the motor was properly broken in.

The majority of the miles were from the Arctic Circle trip where we changed the oil at the recommended 2500 mile intervals. We purchased oil along the way, so while I had started with a high zinc oil ( concentration of ZDDP above 1200ppm), at some point we used a modern oil.

The questions revolved around the cause of the failure. Was it lack of ZDDP in the modern oil, poor quality camshaft material, incompatible lifter material or a mismatch in the lobe profile and the lifter bottom arc. This began a lengthy back-and-forth with a renowned cam manufacturer to whom I sent a few cams and sets of lifters.

The new cam used an acceptable but not the best material.( JCC UK sells a cam with a better steel alloy.) The lifters were also an acceptable steel and compatible with the cam material. This leaves the lobe/lifter profile and the oil as possible issues

In this picture the lobes were blued and a lifter was re-profiled to scribe a line on the lobe. The result gives an accurate position of the center of the lobe versus the centerline of the lifter bore for that lobe. Note that the lifter rides off center of the lobe.

The camshaft lobe does not slope to one side; the toe is the same distance from the heel on both sides of any lobe. By offsetting the centerline of the lifter from the centerline of the lobe, the rotating movement of the lobe will induce spin on the lifter. The distance of that offset will determine the shape of the bottom of the lifter, which could be from flat to some amount of curvature. Too little arc and the bottom will punch in over time; too much and the point load will wear the lifter and the cam.

Take another look at the picture. The first and third lobes are for #1 cylinder and the second and fourth are #2. The scribed lines are on opposite sides of the paired lobes, meaning that the lifter and pushrods rotate in the opposite direction for the opposing cylinder.

Also, the scribed lines versus lobe centers vary quite a bit from lobe to lobe in the Jowett motor. In a perfect world, all the offsets would be the same. A .025" difference in the offset as found on these cams MIGHT require a slight change in the curvature of the bottom of the lifter from one lobe to another.

The lifters as supplied new were flat bottom. My cam guy says that was "not optimum", but that is also his opinion of the offset issues. He reground the bottoms to have a barely discernible curvature.

Both he and I think that the use of a modern low zinc oil was the main problem. He is quite adamant that ZDDP is needed in non-roller camshafts. I had one oil change where we used an oil that claimed to be good for older-style lifter motors, but had just 800 ppm zinc.

Modern oils are far superior than stuff from times past. Here in the States, oils are rated by SAE. The last high ZDDP oils were back in the SH or SJ ratings from decades ago, but SAE states that succeeding ratings are backwards compatible. Current oils are SN and therefore acceptable for use in motors that required at SJ oils. I don't trust that statement. Years back when the ZDDP started disappearing from oils, camshaft/lifter failures were commonplace. The motoring press wrote extensively about the problems.

Caveat emptor.

[David Morris]

Hi Strenner,

Thanks for a very interesting post. Very informative. There are several articles on Google, if you ask for info on the lubrication of flat-topped cam followers.

All the best,

David

[Keith Clements]

viewtopic.php?p=46944#p46944
Is our previous discussion. My opinion is for some reason cam followers stop rotating because they are tight in their bores. When you insert them make sure they rotate and move through out the bore easily. Also check when taking out, if they do not fall out then there may be something wrong. The ones that are stuck will have a groove worn into them.

[Moises]

Thank you all for your interesting opinions on oils. Here in Spain I can buy several mineral oils, but I always use Castrol Classic XL 20W-50 or GTX 15W-40 A3-B3. What is your opinion? Should I add a ZDDP or S2Mo additive?

[Nick Webster]

To start, I am rather disappointed that almost anyone can make up a technical data sheet (tds) when really a standard and comparable one issued by the manufacturer should be expected. So it seems quite difficult to find a useful tds for Castrol.

Generally speaking it looks like Castrol is circa 800ppm which is on the low side. Though they do claim it is sufficient. Due to the difficulties of getting accurate measurement of additives (you can have too much) I think you are better off looking for an oil that claims a higher zddp content as standard, if you think more will help.

I regret that Jowetts did not have a very good reputation for metal hardening when in production and I am still of the opinion that many of the problems that might be attributed to poor lubrication is in fact due to insufficient hardness. Very generally, if the metal surfaces look dented but have an intact skin, (cam followers, valve tips) it is likely a hardening issue. If the metal appears to have "picked up" with a damaged and pitted surface, it is lubrication.

Nick

[alexander]

Not certain if the camshaft damage was due to using a so called classic oil but only two cams showed damage so could have been poor hardening.
Alexander

[Keith Clements]

Alexander,
Worth looking at the followers on the worn cams. Likely they have a wear groove in them, showing the follower was not rotating. Or might even be bad tappet clearance causing high impacts on the cam.

[alexander]

Thanks Keith will check followers , the car is in storage at the moment but hoping to get it back later next month.
Alexander

[Moises]

I just discovered that the clutch operating lever fork is coming out of the groove of the throwout bearing. I will have to remove the engine

[Keith Clements]

There are two diameters of ball joint that fit into the fork. Also the hole in the clutch housing can wear to make the ball joint loose. I have bodged a repair by using some shim stock or tin can.
I have seen the fork lose one of its bearing ends, but never had the fork drop òut of the ball thrust race.

[Keith Clements]

Also if a thicker gasket than the thin paper one is used between clutch housing and gearbox the extra gap might cause the issue as well as upsetting clutch travel.