Broken welded camshaft 48 minutes WTF?

Thorshammer · 06-22-2005, 03:40 PM

So I know racing parts are just that for racing, no responsibility for their manufacture. But I am asking for the guidance of this board. If the guidance is suck it up and bend over, I'm okay with that.

I bought a pair of welded cams from a known Porsche aftermarket cam grinder. It is my 3 rd set from him with the other 2 sets (pairs) for dyno work only. The other two sets are very similiar lift but the duration is different, on the last set the lobe centers were changed per his recommended. Same spring combination, same cam towers. The grinders spring package with titanium retainers, set up to his specs. 110-120 spring seat pressure with 310-340 over the nose at .500 lift. These are three bearing cams and towers. My specs are 112lbs seat pressure, and 320lbs over the nose at .500. The cams are in my 914-6 EP SCCA race car.

Heres the beef: 48 minutes of run time on this motor and the 4,5,6 camshaft breaks just aft of the center cam journal. and broke again in front of the rear journal, as a result of the first break I am sure. I was in 3rd place at Lime Rock Park, and running some really good lap times. It happened about 6800 RPM, and did not cause any other damage when it happened. No piston marks, 4 % leakdown, no valve damage.
After removing the broken cam, I inserted a standard camshaft and it spun perfectly in the housing.

What is real interesting is the dyno cams have over 40 hrs each on them and are not broken and in excellent shape. These cams have 48 minutes of run time. I am aware of the techniques used to straighten welded cams. It is archaic. Where the break occured the cam has a flat "impact mark" right next to the middle journal. After a few years doing destructive and non destructive inspections while serving in the Navy, the crack origin is very clear. What really pisses me off is, I just got porked for full pop retail to get a new cam ground to match the old one. Anyone else ever see this. In the 30-40 porsche engines I have built, I have never broken a camshaft. Am I being a putz, or should something be done here.

One last thing, when I asked for the broken cam back, the grinder told me they could'nt tell anything from it and threw it away. All this after I next day aired the cam to him to have him look at it. Then he said he had a core to grind on, then the next day he said he did'nt. NExt day air a core camshaft. I am aware of new chilled iron billets, and have ordered a pair ground to a different spec. More dyno time.

What would you do???

Erik Madsen

yelcab1 · 06-22-2005, 03:47 PM

Post his name so we can avoid him is the first step.
If he does not stand behind his work, then he is not worth this spit.

TimT · 06-22-2005, 03:53 PM

I think your camgrinder should offer some sort of price adjustment for your new set of cams.

Just venturing a wild guess but the second break occured because of the first break.

Part of the cam broke, valvle spring pressure stopped the boken part, then the part of cam that continued to rotate impacted the stopped part, and the remaing piece of shaft broke.

One would think a vendor that you have a history with would work with you on something like this

Jeff Alton · 06-22-2005, 03:59 PM

Hmmm, strange, I have not heard of any breaking cams either. Were these your cores that were ground and is it possible that they had a flaw prior to the welding and grinding? Just fishing here for ideas.... Obviously the "dyno cams" you are happy with. You are obviously a repeat customer of his so I would think the two of you could work something out. Try to take the fact that you were having a good race out of the equation, and see if there is a resolution that suits both of you.

Keep us posted, and you are to be commended for not saying who it was until it is totally resolved one way or the other.

Jeff

Joeaksa · 06-22-2005, 04:14 PM

Any good tech does not "simply throw the old parts away" without having a reason to do so. He should have asked you first, period. After you spent the money to overnight them to you he knew that they were important.

Personally he just lost any chance of my business. Might even buy a set of Michelin tires before buying 911 parts from someone like this!

JoeA

scottb · 06-22-2005, 05:14 PM

Maybe I've been a lawyer too long, but my guess is that he threw the old cam away to preclude the possibility of it being used in a lawsuit. My $.02, anyway.

asphaltgambler · 06-22-2005, 05:18 PM

So who is it??

randywebb · 06-22-2005, 05:25 PM

in some states it is illegal to not offer the used parts to the owner; check it out for yours

and yes, post the name

jluetjen · jluetjen's Garage

Eric;
Given that it's a "well known" camshaft supplier, I agree that it's most likely not beneficial to reveal the name. If someone really wants to know, I'm sure they'll PM you.

I would take up the point that given that you paid for the camshaft that was broken, and he threw it out, he really should make it up to you. It was your property, not his to throw out.

camgrinder · 06-22-2005, 06:05 PM

For sure it isnt me... I do not need to weld 3 main cams because I have billets

I have seen some broken welded cams before. Usually its when someone welds up an early solex, or other center drilled camshaft.
However, I have seen them break at the corner of the bearing journal where the lobes were side dressed after welding. The "flat impact mark" you refer to could have been ground into the core by a side dressing wheel. This might leave a stress riser.

Not to replace it free of charge is a mistake to me, especially a repeat customer.

scottb · 06-22-2005, 06:14 PM

If you paid with a credit card, you could always dispute the charge. Just a thought....

Thorshammer · 06-22-2005, 06:41 PM

I prefer not to mention a name until this is completely resolved. The cam was NOT ground by "camgrinder". I include this to let any one know that he was not involved.

I started using the current grinder due to my past experience, and the fact that another EP competitor with the same engine was using a particular grind. So with this in mind, I ordered what was being run at that time, only to find it less than adequate. After three iterations and many hours dyno time. The current grind was pretty good. Ramps nice and smooth, duration a little long, but the latest camshaft was the best grind so far.

Usually "no warranty" applies to racing parts, and I do understand this concept. I administer warranty policies and procedures everyday. However, if I have a long term customer, I will normally do what it takes to preserve a business relationship. It seems as if that is not this companies MO.

I am planning to attend the SCCA Runoffs this year and currently sit 4th in the points for my region. I will get my new chilled billets by then, and they will be in the car if they pass the dyno test phase. More Money, More Money. Racing is fun!, Repeat mantra, Racing is fun.

Hey, cam grinder, want to look at a broken weld up and tell me what happened???

Erik Madsen

camgrinder · 06-22-2005, 07:03 PM

Hi Erik,
Of course I will look at the broken cam. IF you can get it back.

Nitrometano · Nitrometano's Garage

What can be the cause to the broken camshaft? A bad welding?

camgrinder · 06-22-2005, 10:04 PM

Camshafts undergo a lot of stress when they are welded. They can sometimes bend over .020". One way to re-straighten the cam post welding is with a hammer and a blunt chisel. This can be difficult to do on some shafts. It is important not to leave any chisel marks or sharp angles which lead to stress risers.
Another possibility is a stress fracture induced in shipping the part. If the parts were inproperly packaged, or dropped at some point a small crack could develop leading to this type of failure.
Btw.. the hammer and chisel method has been used for years to straighten crankshafts and camshafts.

jluetjen · jluetjen's Garage

A hammer and chisel to straighten something as stressed as a camshaft or crankshaft???? Yeeeee!

It reminds me of an old expression which was attributed to Count Bismark:

Quote:

Laws are like sausages, it is better not to see them being made.

I guess that I'd now put camshafts and crankshafts in the same category!

Joeaksa · 06-23-2005, 05:10 AM

Quote:

Originally posted by jluetjen
A hammer and chisel to straighten something as stressed as a camshaft or crankshaft???? Yeeeee!

You should see how they repair aircraft propellers. Same way but with a bigger hammer. Saw it one time and left the place. Could not watch anymore...

Joe A

BURN-BROS · 06-23-2005, 05:20 AM

The hammer and chisel method is similar to how I straighten my extended tool holders. I put them in the mill and spin them up and have a dial gauge on the shaft to check runnout. I then tap the tool with a hammer untill the dial reads 0. Works great.

scottb · 06-23-2005, 05:58 AM

I once had an improperly ground crankshaft let go in two places. The only problem was that I was 1500 feet in the air! Now that's what I call a high pucker factor.

camgrinder · 06-23-2005, 06:50 AM

Its not as bad as it sounds. The chisel has a very blunt end, and the pounding is fairly light. Light enough that is wouldnt drive a nail into a 2x4.
Most 911 cams are straight (less than .0005" runout). The bent cams are usually within .002". If you look at some of the earlier 911 cores, (pre 1980) some have marks along the barrel from a similar straightening process.