Lotus Elan

Steel verses cast cam followers

PostPost by: rgh0 » Thu Apr 14, 2016 9:59 am

Steel cam and steel followers can work together provided a number of things are done. Steel cam followers are good as they are stronger and lighter and can be supplied in thinner top pad thicknesses which are needed for high lift cams.

I presume the same supplier was all QED if you got QED 420 cams. If you have the following setup its probably OK for steel cams and steel followers:
1. Phosphate or DLC coating - you have phosphate which is good
2. Not too great a spring load - how much is to much is hard to say more than 220 ;bs on the nose leads to failures in my experience but if you have Q55 springs that QED normally supply with the 420 cam you will not have to much spring load
3. Use a good assembly lube - did they give any instruction on this ?
4. Run it in carefully - use a good running in oil

Ideally the cams are 5 or 10 Rockwell C hardness unit difference from the followers which are typically nitrided and around 60 Rc hardness. This small difference in hardness helps to prevent galling on running in also. Personally I would not build a full race engine with strong 200 lb nose load valve springs for high revs with a steel cam but I know people do and I believe they generally use DLC coating on the followers.

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PostPost by: 2cams70 » Fri Apr 15, 2016 1:38 pm

Hi Rohan,

I decided to use the QED race springs rather than Q55 springs hence the nose loads will be higher than with Q55. The bottom end is all steel and the Q55's aren't recommended for high RPM.

I know this is overkill given the power range of Q420 cams but I like things bullet proof plus I enjoy the sound of revvy engines. Valves are sprint size long stem with thin pad steel followers and top hat shims. I note the thin pad followers are slightly longer than standard which I assume will help with wear. Orgers set the head up so hopefully it will all go together OK with spring loads being OK. I gave them the QED specs to work to.

By the way, on another issue, do you have any rules of thumb regarding life of follower sleeves versus the followers themselves? For example should follower sleeves be replaced whenever followers are replaced or would you normally get (say) two follower changes for a single sleeve change. My sleeves were judged to be OK although when I placed two of the old iron followers together I did see daylight at the ends indicating some barrel wear. It's just one of the things that's niggling me a bit now that everything else apart from the head casting is new!
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PostPost by: rgh0 » Fri Apr 15, 2016 9:00 pm

Followers generally appear to wear more than the sleeves but they both wear. If Orgers assembled your head and they were OK with the new follower to old sleeve clearances then it should be all OK.

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PostPost by: SJ Lambert » Sat Apr 16, 2016 10:15 am

Manolis Pattakos has alerted me to a new DLC coating:-

Quote from Engine Expo 2016:

New DLC Coatings Offer Up to 50 Times Reduction In Abrasive Wear

Ionbond will present Tribobond 48 ta-C, a newly developed DLC coating for engine and injection system components exposed to temperatures up to 400 ?C.
Compared to conventional hydrogen-containing DLC (a-C:H) coatings that have been used for many years, the company says Tribobond 48 ta-C exhibits an increased hardness of HV 0.05 >5000 and a comparably low coefficient of friction of 0.2 (under dry conditions). The new coating is typically deposited with a thickness of less than 1.5?m.
Tribobond 48 ta-C is used in high load assemblies where service temperatures exceed 300 ?C and / or where increased wettability with oils, gasoline and diesel fuels is required.
In combination with specifically formulated oils, the friction losses of two sliding surfaces can be further reduced by a factor of 2, compared with conventional DLC lubricated with standard oils. Ionbond have found that the abrasive wear resistance is up to fifty times higher when used at temperatures of 200 - 400 ?C, compared to surfaces coated with hydrogenated DLC.
The new coating is available for high-volume production from the Ionbond automotive competence center in Venlo, NL.

Engine Expo 2016 stand number: 3318
http://www.ionbond.com
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PostPost by: SJ Lambert » Fri Dec 22, 2017 10:28 pm

rgh0 wrote:Attached is a photo of the long cam bolt. The bolt is drilled with a 4mm oil passage up its centre and then side drilled to meet the hole in its centre and with the threads removed to line up with the cam oil hole in the first bearing so oil continues to be fed to the other cam bearings

long cam bolt modification.jpg



The cam itself is drilled and tapped deeper to accommodate the longer bolt which reaches to the rear of the first bearing. The cam is also bored to remove the threads down to the start of the front of the first bearing so the bolt shank is a close fit down the cam to the threads.

The aim of this modification is that the bolt keeps the cast iron nose of the cam down to the first bearing in compression which reduces the bending tensile stress from the chain load which is the cause of it potentially breaking at the first bearing.

The bolt I have used is a standard carbon steel grade 5 high tensile bolt ( three lines on the head) which has proved sufficient.

cheers
Rohan



The tightening torque for these longer bolts remains the same as for Standard length bolts?
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PostPost by: rgh0 » Fri Dec 22, 2017 11:06 pm

Yes I use the standard tightening torque

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PostPost by: Davidb » Mon Feb 17, 2020 6:17 pm

I thought I would disinter this old post since it has some great info in it!

Also, I am in the process (finally) of fitting 420 camshafts to my 1720cc engine.
I got the cams from Newman Cams since they seemed to have a good reputation and a good price (180 quid each)

I also ordered some new followers from Newman-just to be safe. They are labelled "Jaguar" followers. The concern I have with them is that the inside pad is larger than the originals and larger than the adjusting shim. Since the shims in my engine do not quite reach the level of the top of the valve spring retainer this means the follower would be bearing directly on the spring retainer-not something we want to happen!

Any comments?
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PostPost by: nmauduit » Mon Feb 17, 2020 6:38 pm

I don't have a Jaguar bucket at hand to check, but I would first investigate 2 routes: buckets with too long "pads" or possibly valves with too long stems for your application (as you conclude, the bucket must rest on the shim which in turn presses only on the stem tip, not on the collar nor anywhere else of the valve assembly - also shims should not be too thin, 60 thou is about the safe limit I believe).
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PostPost by: rgh0 » Mon Feb 17, 2020 7:39 pm

I would return them and get the correct Lotus folllowers

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PostPost by: 2cams70 » Mon Feb 17, 2020 10:11 pm

Just be aware too that 420 cams are not a drop in fit. You'll need to properly check for valve spring coil bind, etc.
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PostPost by: Davidb » Mon Feb 17, 2020 10:17 pm

Thanks for the responses gentlemen.

nmaudit: In this case the valve stems have been machined down by a previous owner and that is the problem. The valve shims I am using are in the 0.080" range but still below the level of the spring retainer.

Rohan: I am going to hang on to them for now-if I decide to replace the valves in the future I can use them.

2cams70: I had already fitted Q55 springs in anticipation of this change. At Rohan's suggestion I checked with thicker shims installed and things are fine.


I compared the Newman followers to a Jaguar XK cam follower and the Jag items are longer by about 1/8". Otherwise identical.
Harry Mundy was responsible for designing the valve train in both engines, so presumably he saved time by carrying over the Jag dimensions?

These followers from Newman Cams are listed as "chilled cast iron" incidentally.
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PostPost by: Davidb » Tue Feb 18, 2020 12:08 am

OK. I have ordered 8 new steel cam followers from Burton. At twelve quid each it seems like a good deal and interestingly, they weigh almost half what the iron followers from Newmans weigh...

When I examined the followers in my engine I realised they are starting to show signs of wear in the sides.
Also, while all the exhaust valve spring pockets have liners only #4 on the inlet side does!
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PostPost by: 2cams70 » Tue Feb 18, 2020 12:23 am

Note from memory I believe that QED stock both thin and standard thickness pad steel followers. Buttons on the other hand only stock one type. Depending on how things measure up thin pads may be a better fit. It's what I used in my engine with Q420 cams.
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PostPost by: Davidb » Tue Feb 18, 2020 1:29 am

Well, The followers I currently have measure around 0/220" thickness and I can shim the correct clearances with that. The new Burtons followers are apparently 0.221" thick so we should be OK. But thanks for the info-hopefully I will be Ok with the Burtons.
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PostPost by: nmauduit » Tue Feb 18, 2020 9:51 am

Davidb wrote:nmaudit: In this case the valve stems have been machined down by a previous owner and that is the problem. The valve shims I am using are in the 0.080" range but still below the level of the spring retainer.


If valves have been modified with stock retainers, my concern would be to make absolutely sure that no contact can be made between the bucket and the retainer (even down the road when the guides get worn out and the tip can move a bit upon bounce, esp. at max revs... or above).

One way could be to slightly machine the landing pad end diameter so that they clear the retainers (or use different retainers with more clearance at the top), or better but more accurate to slightly shorten the pad length (or get the other thickness buckets, 160 thou I believe - this is what I would do) so that thicker shims (in the 140 thou range I guess) will clear the retainer ...
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