Purpose of Cam Welding

[CanadianSniper]

I havn't had any issues with my SHO it has 300,000 km's on it. However can I be so ignorant and ask why or what people are welding on their cam shafts? Is it that the bolts on the sprocket's are coming loose, and you are welding the sprockets to the cam ? I may have a suggestion if this is the case. Please explain the problem.

 

[whiteman_01]

What happens is the sprockets on the cams come loose, and walk around on the cam. When it gets far enough out of time, the valves slap the pistons, and its game over.

 

[SuperHO]

if you say loc-tite, i'm going to spam your email address to every **** site on the web...some people have run pins through the sprocket and cams to hold em in place, but the general consensus is welding is the best bet.

 

[CanadianSniper]

Alternative

I used to work for the railway, on the locomotives, and had situations like this. I assume the sprokets are not keyed in anyway, just bolt onto the shaft. What we did rather that weld anything, would be to pin them together then sewing the bolt heads, so nothing could move. And you could easily remove or repair at at a later date. Just an application idea for you. It worked for us, in areas of vibration, and where bolts did work loose.

 

[CanadianSniper]

Well yes of course welding would be the best permanent alternative. But for those that don't have this luxury, pinning and sewing is available.

 

[Racer X]

Sewing the bolts isn't an option, as there are no bolts to speak of.

The issue is that the sprockets are swedged onto the splined camshaft. Over time, the splines wear down due to a number of conditions (one accepted theory is that thermal expansion and contraction or the dissimilar metals of the shaft and sprocket over time introduces a clearance which exacerbates the wear issue), and the sprocket eventually slips on the camshaft, throwing the valvetrain out of time. On an interference engine like the V8 SHO, once that sprocket lets go completely, it's game over.

Welding is the best solution; anything else is a band-aid that is going to fail eventually.

 

[nothingtoseehere]

Pinning has been tested ... and failed

 

[stephen newberg]

They are not bolted on, but rather press fit on splines. Hence, there is not bolt to drill and sew. A number of people have done pins by drilling the sprocket itself, and I find nothing wrong with the idea, but a vast majority have simply gone to welds as it being easier and just as reliable. And it is not a difficult weld for any competent welder, though it takes care and caution to do it in the engine, which is the common way, and it never hurts to practice first so as not to overdue anything. You do not want warpage or any burn through on the cam.

pax, smn

 

[stephen newberg]

Pinning has been tested ... and failed

I would guess that some of the early welding did not do well either. There is a learning curve involved. Plus sometimes things are just not done properly. But there is no reason that a well done pin system will not work just fine. Pins are used in many applications that are far more strenuous. But welding is a more common skill and requires a good deal less engineering to make it happen, so it rightly should be the preferred technique.

pax, smn

 

[luigisho]

pictures here

http://v8sho.com/SHO/CamSprocketFailurePhotos.htm

 

[wymjym]

I would guess that some of the early welding did not do well either. There is a learning curve involved. Plus sometimes things are just not done properly. But there is no reason that a well done pin system will not work just fine. Pins are used in many applications that are far more strenuous. But welding is a more common skill and requires a good deal less engineering to make it happen, so it rightly should be the preferred technique.

pax, smn

you are correct but since it was Jasper engines that did the pinning (and they failed) I think we should put it to bed and say 'welding' is the way to go.
wj

 

[stephen newberg]

Oh, I think welding is a better idea, and did so myself, but there is no real doubt that properly engineered pinning will work just fine.

pax, smn

 

[Racer X]

Oh, I think welding is a better idea, and did so myself, but there is no real doubt that properly engineered pinning will work just fine.

pax, smn

I believe the issue here is that there isn't a properly engineered pinning solution for the V8 SHO cam issue, which is why it is no longer a recommended solution for reinforcing the cam sprockets.

Otherwise, there would be a great deal more discussion about pinning as a viable solution.

 

[stephen newberg]

That would depend on who is doing the recommending, by simple logic. Personally, I would recommend welding for all the reasons noted, but that does not in the slightest decrease the viability of a properly engineered pinning solution.

The Gen III community in general went toward welding as the solution long ago and by now a fair number of people have it all well worked out, so there is not a lot of reason to work on other things. This, I would guess, is why there is no longer much discussion of pinning as a solution, not because it would not be viable.

pax, smn

 

[CanadianSniper]

After doing a lot of reading, investigating the manufacturing of the camshafts, I must admit I have never seen such a weak piece of trash! I have looked at automotive, marine, many applications and the design that went into the SHO is sheer garbage. Looking at the pics, the only alternative is a weld, it you don't want severe block damage. Who ever designed these shafts, should receive an engineering award for stupidy! you cannot pin recycled Miller Cans !

 

[luigisho]

They're probably still making them this way. I haven't investigated the v-8 volvo cams closely (other than a cursory photo) but they are a Yamaha designed engine and likely have the same cam setup. Maybe they are designed differently enough to prevent a high failure rate at the camshaft.

There are v8 SHOs with high miles and non welded cams. The failure sample size is just too great of a risk for most of us who aren't big on inconvenient catastrophic failure.

 

[stephen newberg]

I agree. I think eventually every single one of them will walk, but that might be a hugely long 'eventually'. I have read of lthese engines with 300+k on them and still going fine with the original set up and no welding, pinning, etc. But at the same time, there are a good number of reports of sprocket slip induced destruction as low as 60K.

It is not the best design for the attachment, that is for sure, but it is far from unprecedented and I am sure it is going to show up again, if it has not already and we just are not aware of it. Regardless, if you really like the car and do not want to take a chance with it, the thing to do is get it welded.

pax, smn

 

[shodoug]

The main reason that welding trumped pinning, IMHO, is that welding can be done with the cams in the vehicle, and you can find someone to weld them for about $100, if you open the engine up to get to them.

Pinning requires that all cams be removed from the engine and then reinstalled. This adds time and effort to effecting a solution. You are more likely to need to ship them or take them somewhere to have them pinned, rather than have someone show up to weld them.

Another issue against pinning is the difference in the hardness of the shaft and sprocket.

Even if it is a better method, which I do not believe it is, it is not as feasible as welding.

The main reason they fail is not that the attachment method is not robust enough, it is that the attachment method is not robust enough to withstand the forces caused by the gear not being centered on the sprocket. This causes the sprocket to be pulled one way and then the other as the shaft rotates.

If the gear were centered on the sprocket, even with the wimpy design, few cams would have probably failed.

The only welded cams that failed that I have seen pictures of had welds that were unacceptable, even to my untrained eye.

That is, in a nutshell, what I remember from reading the emails over the years that this all developed.

Doug

 

[Ian Macoomb]

Woah, I must have gone over 88 mph in my Delorean because I've gone back to 2002.

Just weld 'em and forget it. Or don't bother. The car is worth next to nothing and really isn't worth dumping any more money into.

 

[stephen newberg]

The car is worth next to nothing and really isn't worth dumping any more money into.

I suspect you are right for on the used market, but I admit I find the full logic of the situation wider. Mine runs like a top and shows no real signs of deterioration. To replace it with something new that is about equivalent would cost several tens of thousands of dollars, so I tend to think of that as being what it is really worth when considering maintenance costs and such. Replacement cost rather than resale value seems to me to give a more full view. I can see looking at it the other way too, it just seems an incomplete picture.

pax, smn