LDT 465 Multifuel. Andy3's Broken Camshaft

[rustystud]

A Spark Test confirms that this cam shaft is of steel and not cast iron.

I got the information from the engine rebuild "TM" . All cams where forged steel, along with all the crankshafts. Though some early cranks where not 4140 steel.

 

[oddshot]

My thoughts - could be wrong. Sharp corner = stress raiser. Cyclical torque loading of shaft causes cyclical deflection and metal fatigue.

An old bull and a young bull were standing on the top of a hill overlooking a herd of cows in the valley below. The young bull said, "Hey Old Man, what say we run on down there and inseminate us some of them cows". "What do you say we WALK on down there and inseminate them ALL" was the old bull's reply.

The idea that the lack of a radiused corner resulted in a stress riser where the cam shaft failed is a good one, but I fear we may be looking at the resulting damage and not the complete cause of it. That being said, I speculate that we have already seen the other parts of story. But all of the information is not in yet, and , as I say, that would be speculation.

You'll excuse me, I have to finish working my way through the herd.

 

[73m819]

Below are pictures of the cam gear and the broken nose of the cam. Please note that the bearing surface does not show any galling or oil starvation, and that this side of the break shows the same crystalline appearance with no evidence of grinding or friction wear.

For the record, the cam's bearing surface measures 1 3/16 inch across. That is a fairly large supporting structure.

My plan is to remove the rest of the cam and get a measurement of the cam bearings. I am sending a sample of the oil from the engine out for analysis and will be cutting the filters open to see what I might find in there. I have friends who can help determine the nature of the break.

I find the place where the cam shaft broke very interesting. A radius molded into that corner could have prevented a possible stress riser, but at this point, this is just speculation.

As the undertaker said, "Remains to be seen".

In pictures 3 & 4 post #6, look at 9:00, I believe this cam had Two events, may be close together but still TWO, the event at 9:00 was the second event, it shows a a twisting of the metal, while the rest does not, It looks to me as if the first event was caused by movement vibration, (the edges, the pulling away of the metal, almost like a slight front to back movement), the cam started to come apart then event #2 (the twisting of the last bit of connection.

I have seen this kind of break that looks just like this from belt drive gear boxes where the end play got to much (thrust washer worn) on either the input or output shafts, when doing a after damage assessment (Hanson Agg. did a ADA on every damaging event) , the broken shaft has the pulled metal look and the small twist spot of the finale break, sometimes you could see that the pulled metal was happing over a period of time, other times very fresh.

Just thought I would throw the above out for you all to think about.

 

[oddshot]

Today I was able to measure the front cam bearing journal AND the front cam bearing inner diameter.

Although I am not stopping here with my tear down, I do believe I have found the cause of the failure.

Here is my post #4 from this thread. I have eliminated everything but statements relative to the measurements I have taken today:

... I did find that I could rock the cam gear quite a bit.

Perhaps I should have been more precise in my words and included "up and down in the bearing".

The TM tells us that the WEAR LIMIT for the ID of the front cam bearing is 2.434".

The measurement of the ID of the cam bearing in the subject engine is 2.440".

Combined with the wear on the camshaft journal this indicates a camshaft journal to bearing clearance of about .009'. The TM indicates that the wear limit is .006".

Although I have not stripped the engine to where I can measure the rest of the cam bearing clearances, I feel confident enough to say that 73m819 came pretty close. This cam shaft flexed over and over again in its bearings until it broke at its weakest point ... that squared off point just behind the first journal.

I would be willing to bet that the oil analysis will come back showing a high babbitt and copper content, indicating bad "engine bearings", but we will have to wait and see on that one.





The pictures I included in post #4 shows that the cam bearing was worn down to the copper ... there is no babbitt on the bearing

 

[Scar59]

Good teardown analysis, that much freeplay/vertical slop would cause tha cam to flex, work hardened to metal, ans shear. Nice work.

 

[oddshot]

The multifuel's camshaft in and out movement (thrust) is controlled by the thickness of the camshaft thrust plate and the clearance between it and the thrust surfaces of the back of the cam gear and the thrust face of the front of the camshaft.

The thickness of the thrust plate is given in the TM as 0.2400 to 0.2420.

The thrust plate in the subject engine measured 0.2420.

This being said, the inside of the thrust plate (the surface against the camshaft) DOES show some wear at the top and bottom of the outer circumference of the camshaft's thrust surface, just below the holes for the mounting bolts. The size and shape of the wear marks makes it a little difficult for me to get a good measurement, but I can catch the worn places with a fingernail. This would indicate to me a possible depth of from .001 to .003". These pictures really show how the nose of the broken camshaft rocked the way I spoke of.

These parts have not been gold plated. The color seen is NOT the true color of the parts in question.

 

[oddshot]

Andy, If you get a free moment could you please post to this thread the indicated miles and hours on this engine at the time of the failure. I know you sent them to me but I can't find the PM.

Thank you

Ted

 

[Coffey1]

So everyone with that engine with for sure unknown mileage or time on engine had better pull cam and check for bearing wear or cam shaft wear.

 

[doghead]

Have you measured all of the cam bearings?

Is the front one the only one with that much clearance(wear?)

Any out-of-roundness?

 

[andy3]

Ted,

I have put just at 2000 miles on the truck in the year I had it. The truck is a 1971 and the build tag on the engine is 2/84. The odometer shows just over 54K but you never know how many times an engine and gauge cluster have been swapped out.

I guess what I read into this is I need to pick up a spare motor soon and have it waiting in the wings?

 

[doghead]

Also, is there any indication of gear wear on the cam gear or the one it mates with?

 

[Coffey1]

Andy would it not be easier to just right now check cam and cam bearings.
Before motor gets KIA.
Or would checking the oil that was in it for the bearing material.

 

[oddshot]

Have you measured all of the cam bearings?

No, only the front one. My boss's wife had a baby and I'm pulling some extra duty filling in. I've not been able to get the engine off loaded from my truck yet.

Is the front one the only one with that much clearance(wear?)

Unknown, see the above question/answer. I do not yet know, but I WILL find out.

Any out-of-roundness?

Not much. I measured the bearing at the 6-12 and 3-9 positions, at point about 3/8" inside both the forward and rearward edges of the bearing. At the 6-12 position the reading were almost exactly identical, fore and aft. The 3-9 positions indicated a half a thou or so less wear. There was no visible wear line that would indicate a wobble or rocking of the journal inside the bearing, nothing that I could detect with the naked eye.

Due to the oil grove in the center of the cam's front journal, I didn't think it worthwhile to measure at the center of the bearing.

 

[oddshot]

Also, is there any indication of gear wear on the cam gear or the one it mates with?

Nothing visible. I checked pretty close, and could not see anything. I'm sure that there must be a clearance between teeth spec, but with the camshaft being broken and rocking up and down, I was unable to check it.

Were I to rebuild this engine, I think I would actually try to reuse these gears, but only AFTER I measured their clearances.

 

[Squirt-Truck]

Excellent work.
My metals guy says:

Low stress/high cycle fatigue.
Been cracking for a while.


aka Rotating/bending fatigue, fits with the noted movement and dimensions of the front bearing. Bet the other bearings are in spec.

 

[oddshot]

I wouldn't jump to any conclusions about developing a PM out of what I've found on this tear down, not just yet any way. There is still too much work to be done.

Heck ... the other 90% of the camshaft is still in the block.

Also, remember that this is only ONE engine and the only one I've ever seen torn down and measured due to this type of failure.

I would LOVE to do another tear-down on an engine with a suspected broken cam.

 

[andy3]

Coffey1 I think I will do an oil analysis in the next 60 if the peanut gallery thinks it prudent. I was thinking of going ahead and repaacing the spin on filters with fresh at that time as well.

 

[Recovry4x4]

While camshaft failures are not the norm, they are not isolated. Broken crankshafts seem to be more prevalent in the White engines and now I'm wondering about camshafts. I would think regular oil analysis might catch bearings going away.

 

[Coffey1]

What would be good if you knew where oil was that came out of your new engine and get it checked.

 

[oddshot]

What would be good if you knew where oil was that came out of your new engine and get it checked.

I have a sample and its getting analyzed. I also have the filters (spin-ons) and will be cutting them open to examine the entrails.