Kasenit

[Walt Fricke]

Could one use Kasenit on, say, rocker arm wear faces? For that matter, on the cam lobes also? It apparently can case harden down to 0.020 or so if you keep at it. Heat area to be hardened red hot, put into the can of the stuff (a powder?) or pour it on, quench (or reheat and repeat).

Cam lobes? Would heating them red hot one at a time warp the cam?

I noticed it in an ENCO ad, but Google showed gunsmiths and some machinists discussing having used it effectively for surface hardening of small parts.

Walt Fricke
(thinking about all the rockers he has that have started to pit on the surface, and how if they are reground they might benefit from hardening that surface)

[Dennis Kalma]

OK Walt, you may be the only guy in Christendom as cheap as me...but why wouldn't you just replace the wretched things?

My wooden head suggests that the risks of a non-hardened lobe/arm wearing and dumping a whole bunch of metal into the engine would outweigh the cost savings....

But then again, industrial hardening processes are not exactly rocket science, so it might work? I will watch the thread with interest...

Dennis

[Walt Fricke]

Possibly cheaper.

I have a whole bunch of these that have started pitting or showing some kind of wear. Not bad, but needing to be refaced. Some to be rebushed first. I don't see these as throw away items.

I may have this all wrong, but I got it in my head that neither the cam lobes nor the rocker faces are hardened to start with. But that as they wear against each other they harden each other, at least, literally, superficially. And part of the drill of breaking in new cams/rockers. That's the hadening that pits and such have gotten through.

So why not start off hard. Of course, there may be a very good reason not to do this. If so, someone will point this out.

Walt

[Dennis Kalma]

Again, curious. I always thought that cams were surface hardened which presents the rocker with a very thin, very hard surface that wears slowly. Once you get past the hardened layer then it goes more quickly.

I had a Honda where they replaced the cam under warranty as the lobes were improperly hardened and suffered premature wear. While the dealer did not keep my cam, he showed me one that allegedly had worn due to the same problem and you could see that there was a valley worn in the cam. I say allegedly as I was suspicious of the dealer and asked a lot of questions and demanded follow up....which I got most of.

Also in Wayne's book there is a photo of a newly reground/hardened camshaft.....it does LOOK different!

Dennis

[Walt Fricke]

I think I had that same picture in the back of my mind. But the reground cams I have purchased didn't look like that. They looked just like welding reground. Maybe they were polished after being nitrided or something?

We'll learn.

When the hardening on the cam (however it got there) goes, you are right - things go quickly. A machinist friend showed me a 911 cam where the oil spray bar hole had gotten plugged. The cam was worn down to the base circle, except for two paper thin perfect cam profiles on each side of the lobe where the rocker did not contact it. Very delicate, they were. It happened in a day or something like that, supposedly. Of course the lack of lubrication had to have had a hand in the speed of the wear.

Walt

[chris_seven]

Walt,

Interesting set of questions and potential problems.

Kasenit is a relatively simple compound that basically allows carbon to diffuse into the surface of a steel when heated above about 850 degC (Sorry for the funny units). It needs to be this hot as ferritic steels have a phase change around this temperature and the solubility of carbon increases significantly. The amount of carbon that will diffuse into the surface depends on the time at temperature (Fick's 2nd Law of Diffusion if I remember correctly).

The idea of heating locally probably won't work because miniumum time would be around 30 minutes and to gain significant depth can take several hours.

The next issue would be the carbon content of the original part. If the carbon level in this part is greater than around 0.2% there really isn't much of a thermodynamic driving force to cause diffusion and results are likely to be poor.

If you could produce a layer of carbon in the surface you would then have to quench the part in a light oil or preferably a modern polymer material such as HoughtonAquaquench.

Finally would would have to temper and stress relieve.

All of these process would need to fairly well controlled to give successful and repeatable results.

If we consider rockers: I thought most 911 rockers were cast and they are likley to have quite a high carbon content and if this is the case they won't respond very well to case hardening. They are also quite likely to distort when quenched.

I would think that stellite hard facing may be a better option but more difficult to do at home.

As regards cams the problems are similar and it is unlikley that you could have sufficient time at temperature to make this process work.

Some performance billet cams made from steel are gas carburised but they invariably bend during quenching and need to be straightened before final grinding.

A large number of production cams are cast and lobes are hardened using chills placed in the mould. These chills rapidly cool the cast iron in the region of the lobe and cause a 'white iron' structure to be developed. White iron is very hard and wear resistant. The rest of the cam is grey iron and is more ductile and shock resistant.

If you regrind such a cam gas nitriding just won't work successfully. You will produce iron nitirdes on the surface and they are very brittle and likely to spall. I think it may be possible to either plasma nitirde or boronise but this could cost more than new cams.

If I had a reground cast iron cam I would Parkerise the surface which would give a good self lubricating layer with excellent oil film retention.

Race cams I would make from a high grade nitriding steel and gas nitride.

Hope this helps

[tctnd]

The cam/lifter interface is challenging to lubricate under the best of circumstances and the composition and hardness profiles of these components are typically chosen by drawing on long experience. I aplaud your enthusiam for experimentation (I do it myself) if that is your true motivation. As an economy measure however this would not be a good bet; very small cost saving vs substantial risk of catastrophe.
regards,
Phil

[cnavarro]

You could DLC the rocker face which would provide a reduced-friction surface treatment, but the rocker must be properly reconditioned or new - the substrate onto which the treatment is applied is bad, there is no hope for it. We tried many coatings and platings in an effort to reduce cam and lifter wear in flat-tappet engines. In fact, the best solution we found was to use a used lifter, resurface, cryo, and ion nitride the surface which worked well with how the cams were ground and hardened.

[911pcars]

Charles,
How about some innovative enterprise create a rocker arm with a roller tip for the cam lobe? Should help reduce internal friction as well as provide an optimum wear surface for the cams.

There was a thread awhile back describing such a rocker arm. I guess like many projects, they become still-born.

Sherwood

[cnavarro]

I have wanted to make self-oiling roller rockers for the Porsche 914 for years - the biggest hurdle is cost and that there already exists a product that serves the same purpose, sans oiling. Most people don't realize that on the 914, the rocker has little galleys that distribute oil to the adjusting screw and more or less splash lubricates the spring, retainer, and valve stem at low rpms. Higher rpms aren't so much of a problem, as the valve cover gets pretty messy with windage. It's hard to bring a product to fruition, do it right, and have it priced such that it sells, that is probably why many good ideas never leave the drawing board. That said, I would love to make it!

[914efi]

I have also wondered why with all of the cool aluminum roller rockers out there for other cars that somebody hasn't done one for 911s. Seems like a no brainer. Probably not needed, but that never stops anyone.

[Walt Fricke]

Thanks for steering me away from the quick and dirty - Kasenit - for this application. The rockers are cast (mine are, anyway, and I don't think I'll be switching to the forged ones, even assuming I could find some).

Looks like the options (leaving aside the issue of cam compatibility) are DLC or cryo/ion nitride. Or leave them alone.

I have a bunch of rockers I hope to have resurfaced - I just checked their bushings with a new rocker shaft, and compared with a new rocker the shaft did not wiggle noticeably more despite the fact that it was easy to see where the wear was on the bushings - nice cross hatching up top and sides, smooth on bottom. (I also have a whole set of rockers with good faces, but which had a lot more wiggle - these will teach me how to rebush).

I think I have a friend who used roller rockers on a 914. He moaned a bit about it - over engineering or something kept him from getting the engine running in a timely manner, or innovation caused problems that had the same result.

But is there an OHC engine that uses rollers on the cam lobe? The pushrod engines use the roller on the valve. Though they also can use them on the tappets, so I guess a roller is not inherently incompatible with following a cam lobe.

Would there be anything worth the effort to be gained by replacing the elephant foot with a roller? I don't see significant wear on either foot or stem. Certainly not pitting, as on the cam and rocker faces.

To be really worth while, I'd think you'd need significantly less friction, or less weight, or both.

But maybe just longer lasting parts would be worth the expense. That was all I was looking for.

Walt

[cnavarro]

I wouldn't ion nitride them without checking the rockwell of the rocker and cam lobe and make sure the spread is idea. Cryoing on the other hand, every engine component can benefit from cyroing, especially ones that are cast. DLC is very expensive and I would find another place to spend my money and just use an oil with sufficient Zn and P :-) We reserve DLC for engines where every last iota of HP is being squeezed out OR we are overbuilding an engine for uber-longevity.

The issue with the roller rockers on the 914 are that they do not oil the valvetrain with exception where you have sustained high rpms. Any customer of mine who uses them I more or less state that they need to fabricate oil squirters for the rocker box to satisfy the need for proper oiling. I learned the hard way when a low rpm street engine of mine ate up valve guides and ended up seizing an intake, and doing lots of damage along the way.

OHC engine inherently have less frictional losses than a pushrod engine, so i'm not sure what gains if any would be had with roller rockers.

QUESTION? Are 911 rockers self oiling or pressure fed? I've never held one in my hand, so I can't answer that myself.

[Walt Fricke]

All 911 rockers before the 964s are self oilng. They have two oiling holes. When you rebush you drill out the bush where the holes are.

At some point Porsche routed pressurized oil to these. Perhaps in conjunction with the cam box oil line restricter. Which poses the question of whether those of us who rushed to install these restricters on our older cars may have increased rocker shaft/bushing wear a tad.

Walt

[911pcars]

WebCam advertises refurbishing worn rockers by hard welding the tip, then regrinding. However, one could buy new rockers cheaper than what they charge. You might be able to have this done on your own.

Sherwood

[Walt Fricke]

I had someone other than Webcam in mind, though don't know the charge there. Perhaps WC includes the cost of rebushing in this? For sure, if no one will regrind for less than the cost of new, who would mess with this.

[911 tweaks]

update please...

ALSO

Has anyone answered the question brought up by Walt:
...all of us rushing to use the cam box oil line restricters to increase oil pressure, WELL, has this contributed to or created acceleration of wear on the cam lobes, rockers, rocker bushings, valve area or any other parts in this area?

Thanks! Bob