new 5/17/03, 5/18/03
The engineer in me (MSEE, and have had a eng. position since '89) wants to be sure of the root cause of the problem. The mechanic in me (associate's degree in automotive tech, certified ASE and Toyota master tech, worked on Toyotas from '78-'88) wants to know the long term prognosis after welding.
How do we know that the gear slippage is the root cause? Could it be the cam seizing in the bearings? Could it be a valve sticking closed? Could it be slop in the chain causing the cam timing to be off so much that a piston and value collide? Some other mystery problem? I know these are unlikely, but how do we know that the root cause is the cam/gear design?
How were the ones that had the problem maintained? Did they have frequent oil changes? How were they driven?
How does the engine hold up long term after the cam weld? How many miles do folks have on their sho's after the mod? Doesn't the welding process warp the cam? Doesn't it put the cam out of balance? Isn't there an aftermarket cam replacement?
I worked as a Ford tech for a while and find it hard to believe that Ford doesn't redesign the cams if they are the problem.
I haven't even changed the oil myself since getting out of the mechanic business but am starting to get the bug to work on my own cars again.
Thanks for your time,
All right, I'm going to answer, since I'm sitting at home, and hopefully if I'm wrong about anything, the rest of the crew will correct me.
Q: Is gear slippage the root cause?
A: It's the best we can come up with. Pictures of spun cams and my personal inspection of my own reveal that the cam sprocket is not welded to the cam shaft. There are splines on the shaft and on the sprocket which make an interference fit. However... the loading on the cam sprocket is asymmetrical.
The theory goes that the uneven loading on the sprocket induces a side load against the splines which they are not designed to resist. Therefore, over time, the cam sprocket is "walked" down the splines, causing them to fail. Also, it is known that the sprocket and the cam shaft are of different (though similar) materials, with different RC's. It is my PERSONAL theory that in addition to the side loading, thermal expansion differences between the sprocket and the shaft splines allow it more "play" thus exacerbating the problem. The spines on my sprocket were fine, but the splines on the shaft were snapped off at the base, which leads me to believe that just like snapping a paperclip, enough play will break anything.
Q: Could it be the cam seizing in the bearings?
A: No. Now, hopefully the list does not go through another cam bearing spasm... but here's why. The 3.4L V8 doesn't have cam "bearings", per se. The cam shaft actually sits in a cupped section of the block, directly on the block. The only thing between the shaft and the block is a film of oil. There are no "bearings" (defined as a separate part specifically designed to reduce the frictional load between the rotating shaft and the stationary block)
Q: Could slop in the chain cause the timing to be off?
A: Perhaps, but if that were so... why would the car chatter before the cam slipped? Why would the splines show such damage, and the cam lobes none? None of the post-damage evidence points in the direction of a timing failure.
Q: Could a valve be stuck?
A: Perhaps, again, but when I lost my cam, I had 4 bent valves, a cracked piston head, and a scored cylinder wall, in addition to the trashed cam. Try explaining that with one stuck valve.
Q: How were the victims maintained/how were they driven?
A: All ranges of maintenance and driving style. Some individuals have lost multiple cams. There are racers whose engines have held, and suburbanites (without teenagers) whose engines have not. Controlling the statistics for driver age, style, or maintenance yields no significant data changes.
Q: How does the engine hold up after a cam weld, how many miles after a weld?
A: There are three flavors of cam - stock, welded, and pinned. Members of the list donated a few of each kind to FOMOCO for destructive testing. Supposedly the results for the welded cam were 1.5 million miles, and the pinned cam somewhere about 4 million miles, with the stock cam coming in somewhere way WAY below both.
Q: Does the welding process warp the cam or unbalance it?
A: Not if it's done correctly. Some people have warped their cams by welding them improperly, but most of the experienced professional welders have not. The balance of the cam is not affected by a proper weld, since the welding takes place evenly at three (or four) equidistant points about the center of rotation.
Q: Is there an aftermarket replacement?
A: If there is, no one has found it yet. Your best bet is modify the cams you have. Supposedly, years ago before all this happened, someone took one of our cams to Crane cams, and asked them to build a better one. They said there really wasn't much they could do. Rumor only. (not a rumor - I called Crane Cams - Buford)
> I worked as a Ford tech for a while and find it hard to believe that Ford
> doesn't redesign the cams if they are the problem.
I'd like to believe that as well, but the simple fact is that the Ford you worked for and the Ford who is running the company now... are probably totally different companies. Sorry to disappoint, but imagine how some of us feel.
Frank in OKC
96 ES (RIP)
The problem seems to hit any V8 SHO, regardless of how it was treated, maintained, etc. And yes, we are sure it is the sprocket coming loose. It has been shown in every failure, I believe, that the cam sprocket is loose. As far as I know, there have been no ill effects from a properly performed weld job. Naturally, if you get all sorts of bits of welding metals into your cylinders and the cams are welded poorly and you put the car together wrong, you're going to run into problems.
How do we know that the gear slippage is the root cause? -Evidence on the shaft is consistent with the sprocket walking - every damaged shaft is consistent. Could it be the cam seizing in the bearings? Could it be a valve sticking closed? Could it be slop in the chain causing the cam timing to be off so much that a piston and value collide? Some other mystery problem? I know these are unlikely, but how do we know that the root cause is the cam/gear design?
How were the ones that had the problem maintained? Did they have frequent -As a group, you probably have noticed, we drive em hard, and overcare for them. Oil changed ! in mine every 2-3K, tranny twice a year etc oil changes? How were they driven?
How does the engine hold up long term after the cam weld? How many miles do folks have on their sho's after the mod? Welded mine last October have put 40K on the welds.
Doesn't the welding process warp the cam? Doesn't it put the cam out of balance? Isn't there an aftermarket cam replacement?
I worked as a Ford tech for a while and find it hard to believe that Ford doesn't redesign the cams if they are the problem. If ford were to do that, it would be tantamount to an admission, why do you think I'm suing them? Go back to V8sho.com and read some of the stories as told by the people this has happened to. See how Ford treated them. Make up your own mind based on what you see there.
All responses IMHO.
Good Luck - Get em welded soon.
I haven't even changed the oil myself since getting out of the mechanic business but am starting to get the bug to work on my own cars again.
Thanks for your time,
No, this one is pretty clear Charles! I'm a victim of the camshaft "spin". It cure is either welding or pinning the sprocket to the shaft. Do it quick, it's money in the bank because a, meaning 1, camshaft spin is between $3K-$8K depending on collateral damage. Mine was $6K. I replaced one head, two camshafts and 16 valves. I still had two other the other cylinder bank! I welded mine this Jan 2003. Other started welding a couple of years ago.
We've only seen a handful of cars that were welded fail. And that was due to "DIY"ers with no experience. There are now a couple of cars into 50K+ post welding mileage. With two years we'll have cars in the 100K+ post weld club. I think Tim Wright mention that there are about 500 now welded. (closer to 1,000 this spring - Buford)
Even the guys welding on a regular basis do trial welds before every cam job on old broken cans to make sure the temp and material is perfect. The sprocket and the "shaft" which is a pipe, are different metals, so there is a little bit of skill it this procedure.
My advice, get it done! One, you'll likely save a ton of money in the long haul, and two you will feel better about it knowing it's done. See v8sho.com for a list of welders that have been used by the v8sho gang. I not saying this to scare anyone, I'm saying it to save others what I and hundreds of others have been through.
If you or anyone else reading this, have any questions, don't hesitate to throw me an off list email.
As you have read, this is a real problem.
As a reasonably good mechanic with a good basic background in engineering and logic, I can tell you that it is a faulty design on the sprockets that are in the secondary chain system.
The main cam chain is a very durable design and is not giving noticeable problems at this point. The sprocket just starts to work loose. As it moves back and forth, it makes the typical "diesel" type sound and eventually gets so much movement that it spins totally. When it does, it cuts what looks like threads in the shaft, leading some to conclude that the thing is screwed on, but it isn't. It is slid on in a very slight interference fit, and then the main cam pipe is expanded INTO the teeth on the inside surface of the sprocket (same for the lobes, but they don't get the same amount of force applied to them so they don't appear to be failing).
I have held a failed cam in my hand that you can spin the sprocket with a flick of the finger like a top!
It isn't maintenance, although many Ford dealers and Zone reps have blamed the customer for it. Most failures have happened to normal NON club people. Most club people found out about it and have had their welded (majority) or pinned (some).
Welding is a proven fix, although we won't know how the 50+k health of the fix is for a while as you have read. The logical assumption is that once you stabilize the sprocket so it can't start working loose, it probably won't ever come loose.
The VERY few that "repaired, and welded cams that have failed were:
a. Someone welding a badly loose sprocket (not recommended)
b. tiny spot welds that are cold and not deep enough.
Balance? Not a problem. You are talking about roughly evenly spaced welds within an inch of the center of rotation and a tiny bit of metal.
Bearings failing? Just to clarify....although there are no removable or replaceable cam bearings on the V8 SHO, there are bearing "surfaces" . The cams ride in the head material itself with a cap on top, and no removable or replaceable bearing in the cap. Seems to work, the few motors beyond 100k that have been torn down don't appear to have a problem in this area. Those motors we have seen that have had a cam failure show no sign of a problem in the bearing area, and no sign of a loss of lubrication.
Stuck valve? If a valve stuck then it would bend and nothing else would happen, and if the cam was designed right, it would not fail when an valve sticks. BUT when this problem happens, usually all 8 valves on that cam are bent, sometimes fewer.
NO, we have seen this problem and it is the cam sprocket mounting design.
Unlike some, it will take a LOT for me to believe in Ford again. When a company abandons 20,000 enthusiast owners that bought its premier high dollar sedan, then the company makes a statement. I don't like that statement and it makes me sad that Ford would have such shoddy business ethics.
They would have ignored the Cobra folks a few years back but they still planned on making Mustangs and SVT vehicles. Too bad they didn't care about their OTHER enthusiast group.
I love my 96 SHO despite what Ford is doing (or not doing) but I doubt much if anyone in my family or anyone I know will be darkening a Ford dealership ever again.
One engineer I talked to said in addition to the side load issue, placing the sprocket so far from the end of the shaft will result in randomness as far as the quality of the bond is concerned. Some sprocket-to-camshaft bonds would be marginal from the start because it's difficult to consistently get an excellent swaged bond that far from the end of the shaft. He said he would expect some of these camshafts to last a really long time and others to have a very short service life. Some SHOs trashed out at 20K and others are apparently still running at 100K+.
This guy has worked many years designing and testing large scale chemical industry equipment that costs a lot more than our V8 SHOs. He said the sprockets should have been pinned. Just his $.02 after a shallow 10-minute conversation, but I thought it was an interesting comment from a neutral observer who has never been involved with SHO or Ford.
I've followed this engine defect discussion for about a year and a half, waiting to see what Ford was going to do and what would happen with the welded cams. I have concluded that welding is less risk than not welding.
Ford doesn't care, because they only warranted the cars for 36,000 miles or 36 months (longer for ESPs). They can walk away with clear reptilian corporate conscience. I'm not going to forget this, though. It's always been rule of thumb that a V8 engine sold under a Big 3 nameplate will last 100,000 miles or more. Even the 60s and 70s rust bucket POSs could manage that to do that with minimal expense. I don't look at a new Ford without wondering "What is Ford ska-rooing us out of this time?" Whatever vehicle I buy, I have to be pretty certain that I can get 100K miles out of it before replacing an engine or transmission. Most West Virginians I know take out 60 or even 72 month loans and put 15K to 25K miles per year on their cars. It puts a whole new spin on the new car buying process if one starts to suspect Fords have 36,000 to 50,000 mile engines and Ford won't honor their own ESP warranty. If that's the reputation Ford, wants, I don't care. I have no problem driving any other nameplate that runs.
Ford has totally disgusted me with their arrogant denial of poor camshaft design in this car. I think if they can warrant the 3.8L V6 for what, 7 years/100,000 miles?, AND they can replace multitudes of 3.8L engines damaged by a leaky head gasket (keeping in mind that many of those owners got more than one replacement, too), Ford can step up to the plate and fix the V8 SHO.
'98 black cc
I think you may be opening a big nasty can of worms here my friend.
We have engineers, master mechanics, analysts, machinists, designers, draftsmen, chemists scientist, PhD's and even several Ford employees on this list that have done a lot of homework on this problem over the last 2 and a half years. Some have spent their own funds and in a few cases I believe even jeopardized their employment with regards to this issue.
As far as the insides of my engine when the sprocket let loose at 95, 000: I still had honing marks from the factory on the cylinder walls, main and rod bearings were still in very serviceable shape, cam spun free and easy when not compressing springs, the interior of my engine was devoid of deposits of any kind. Changed oil religiously every 3,000 miles.
I would suggest if you are that skeptical that you ignore those of us who have gone before you and blaze a new trail, please show us how wrong we are and drive it into the 200k range without getting some preventative measures performed.
I would however like to remind you before you set off on your lonely trail that until a month or so ago, each cam (still un-redesigned other then the price) cost over $1,000, you also MUST replace the 20 T-T-Y head bolts and the washers or suffer an aggravating continual seepage and head gaskets are only available from Ford at some $370 a set. Of course, if you are rolling in the bucks it would not be a big deal, but the inconvenience of when it decides to strand you may be. I sincerely wish you the best of luck. If I sound a little perturbed by you questions that would be due to the fact much of the aforementioned information is either on the V8SHO.com or NHTSA.com website, not to mention publicized in several publications ranging from the Detroit Free Press to Autoweek. Any review of the websites geared to the SHO will reiterate these findings.
It would also be interesting to note that it did take an act of the Federal government and several multi-million dollar lawsuits to get Ford to do something as simple as reset the width and edging of the guide tracks the Explorer ran down in the factory on those Firestone tires. Wonder why they just haven't redesigned our cams yet?
If memory serves me, Ford did perform destructive test on stock set of cams that caused the engine to "melt down" before it went 75k?
My welded cams have been for 29,000 (with a 9 psi supercharger) and are still going strong.
Yup, one nasty can of worms.
As an engineer you know it's important to review all the data and extrapolate what you believe to be relevant. All that you ask has been asked before, and for the most part answered to the degree of which we are satisfied. I assure you that we are not an easy group to satisfy.
With regards to a Root Cause Analysis, as an Engineer I'm sure you're aware that this group quite obviously does not have the monetary resources to execute such a study. Instead we have concentrated on a cost effective and technically sound preventative measure directed at the primary failure point and I think we have achieved that goal.
Get up to speed on what we've done, why we did it and then provide some feedback. I think you will find that any conclusions we have reached were not done in an abstract manner. Most interested to hear your viewpoints.
Here is your homework;