Cam Followers worn

[wobblyweb]

Hi,
I have just returned from a longish ride out and the engine sounded really tappety. The tappets have been noisy for a while but on inspection 2 of the followers have worn down by about 1.5mm.
What would cause this ??? I had the cams reground a few years ago but did not replace the buckets, they have been OK until now. One other follower has marks like a pencil scribble on the face.

Any advice appreciated.
Pics [/url]http://www.mmcars.info/cam.html[url]

Thanks
Rae

[marcfuller]

Could be from using contemporary automobile motor oils with low zinc-phosphors levels, grades SL - SM particulary. They do not provide sufficent lubrication for flat tappets. What oil(s) have you been using? How many miles do you put on your car annualy?

[wobblyweb]

Hi Marc
thanks for the quick reply, I have done about 4000 for a couple of years but dont use it as much now, so maybe 8000 since the reground cams.
I use castrol foe the 2 twin cams that i drive, not the modern oil.

[marcfuller]

It seems that your tappets have been rotating properly and the wear is even, which would indicate a longer term lubrication failure.

I am uncertain as to what you mean by "the modern oil". The issue is not an oil's brand name, or if it is synthetic or conventional, or even the viscosity. For the last 10 years API graded passenger car oils have been formulated with increasingly reduced zinc dialkyl dithio phosphate (ZDDP) amounts. Particularly the recent SL/SM grade oils of the last 3 years. The reason that ZDDP is important is that it is about the only high pressure lubricant available capable of providing lubrication between the cam lobe and tappet. The reason that the SL/SM oils can forgo a needed level of ZDDP is that newer cars use roller tappets, rather than the flat tappets in our Elans. The reason for reducing ZDDP is the zinc and phosphate reduce the life span of catalytic converters.

To know more about ZDDP and its use in engine oil - http://en.wikipedia.org/wiki/ZDDP

In the last few weeks there have been a number of articles on flat tappet wear and the reduced ZDDP content in API graded automobile oil. I have recently talked with a vintage engine rebuilder who has experienced for the last year customers with the tappet failure you have. And Comp Cams issued a service bulletin last month about the need for ZDDP with flat tappets.

Fortunately, most racing oils and motorcycle oils (BMW motorcycle oil may be an exception), and diesel engine oils have the higher levels of ZDDP that were present when flat tappets were the norm.

[Hamish Coutts]

Marc,

I find this topic fascinating, worrying and a tad confusing.

I am currently running GTX Magnatec 15W 40 (for use in conventional engines). There is a wee white lable on the back of the container saying "meets or exceeds the protection bla bla bla - SAE 15W 40, API SL/CF, ACEA A3/B3 ...."

For a simple non engineer soul like me, is this the type of oil I should be using in a twink that has done 2K miles since a rebuild - and should continue to use? Is there anything that is better?

Hamish.

[marcfuller]

The oil you are using is what the concern is about regarding flat tappet engines.

SAE 15W 40, API SL/CF, ACEA A3/B3 ....
(emphasis added)

I wouldn't use an API SL or SM grade oil in my T-C, or any flat tappet engine. In fact I have a number of quarts of Valvoline API SL grade synth 20-50 I would sell cheap.

Simply because the rash of recent experience that is beginning to emerge regarding flat tappet failure and the reduced level of ZDDP in current API graded oils, I will use Pennzoil or Quaker State Racing 20-50 in my Elan and Shell Rotella T in any other non-catalytic converter flat tappet engines. These oils have ZDDP levels close to what was the standard when our T-C's were new and flat tappets were most common. I would also reccomend the same to any one else. (Note that ZDDP levels will continue to be reduced in future gasoline and diesel oils for passenger cars and trucks. Racing oils are exempted.)

Take a look at the table I posted in a thread last month for more details as to ZDDP levels in oils- http://www.lotuselan.net/forums/viewtopic.php?t=12680

I haven't found a ZDDP additive, nor have I found a non-catalytic converter poisoning ZDDP alternative that is in any oil on the market. Although BG is supposed to be introducing a ZDDP additive later this year.

[stuartgb100]

Hamish,

I'm a little concerned too. The car's done about 7.5K miles since a full engine rebuild by the PO. He used bog standard oil from scratch, so according to Rohan's findings, the damage is probably already done.

As soon as I bought it, I changed to Castrol Classic 20 W 50. I have rung their technical dept, and they confirm there are ZDDP additives in the Classic oil series. He will try to get back to me with details about concentrations, types of ZDDP additives, etc.

Regards,
Stuart.

[marcfuller]

Stuart, I wouldn't be concerned. It seems like Castrol Classic XL 20W-50 is a good choice for older flat tappet engines. Wish I could find it in the US. Found the following info on the Castrol UK website. (emphasis added)

It's API Service grade SE

Castrol Classic XL 20W-50 is designed to meet the motor manufacturers' requirements for passenger cars and motorcycles running under normal service conditions, but excluding those equipped with catalytic converters.

The prime recommendation is for all pre-1980 petrol engined vehicles requiring a high quality product but with an older technology additive formulation.

[steveww]

I was using Castrol Magnetec but I will be draining the sump this weekend anf filling it with Millers Sport 20W50 http://www.millersoils.net/index2.html

[wobblyweb]

I have had a chance to inspect the rest of the head, the other followers seem flat ( checked with a straight edge) so only two as described. Another 2 however are scored. The 2 cam lobes from the worn followers have the edges worn, ie instead of 1/2 inch flat against the follower only the center part touches. pics here..

http://www.mmcars.info/cam.html

I have always used Castrol XL20-50, the info on oil is very interesting but I suspect my problem is not related ???

Thanks

Rae

[marcfuller]

Millers Sport 20W50

Why did you chose that oil? According to the Millers website it appears to be an API SJ grade which has the same ZDDP content and the API SL grade. Do you have a zinc and phosporus amount for it from Millers?

[steveww]

I asked Miller Oils the question about ZDDP and this was the answer I got.

DEAR STEVE
THANKS FOR YOUR E MAIL WE RECOMMEND OUR CLASSIC SPORT 20W/50
AS THE LUBRICANT FOR YOUR LOTUS TWIN CAM ENGINE WITH THE PROTECTION
REQUIRED
WITH THE ZDDP.

KIND REGARDS

ALLAN

The product info page on their web site also states that the oil is suitable for Lotus, Aston Martin, Ferrari and other high performance engines.

Perhaps someone who knows much more about this sort of thing could ask some more technical questions of Millers?

[rgh0]

Rae

Without detailed measurements its hard to be certain but it looks like your tappets and the sleeves in the head they run in have worn allowing the tappets to rock in the bores. This overloads the edges of the cam where it meets the rocked over tappet leading to the failure.

IMHO I personally do not think the failure relates to the oil being used just normal wear leading to misalignment then overload and failure.

Rohan

[wobblyweb]

Thanks Rohan
I have looked at the followers and the 2 worn ones are indeed loose in the sleeves.
I cannot measure the clearance but fitting another follower reduces the movement.
Hopefully its the followers that have worn not the insert.
I will try 2 new followers.

[twincamman]

could it be the refacing removed most of the heat treated material????? ed