DP #24 Engine failure....

[Chris "drooze" Wertman]

Well, I will only say this in as much as my possible "theory" of how and what may have caused the whole debacle to occur, and this comes from my experience, albeit in a different design engine, we see it happen all the time, at extrodinary revs (usually 12k) with a trans or clutch breakage where it freespins, then the valve contact the piston, on an engine with a stable valve train to 15k in these cases however the damage to the bearings can be seen at times, they are rollers, and different granted, seen it too many times to count, those are however ohc engines, and of older design BUT that is what led me to consider it as a possiblity.

Now......after talking it through with a couple of others on the phone....I still cant say the PTV occured before or after. BUT you are correct and that was one thing I didnt consider it was mentioned to me on the phone, and I think Art mentioned it too. Either when it lost its bearing or.
But it did do pretty massive valvetrain damage, a broken shaft and split the rocker shaft mounts in 2 so it was a pretty substansial hit, that was also what partly led me to believe the rod was still with bearing and solidly affixed to the crank.

The other reason is the location of the hit on the piston IN the exhaust valve pocket at say 2 degrees retrded there is a PTV issue on the exhaust.


In as much as the wrist pin seizure, what is left of the bosses on the piston are clean with no galling. I think it was a "wood chipper" effect of the rotation of the crank afterward removing the pin and rod from the piston. Just from what we see.

To me, the rod failure is a symptom of something, not the cause, I dont think you are saying any different and I have drawn no lines in the sand and am only trying to have a working theory.

But the rod bolt failure and the piston to valve contact is a plausible explanation. The rod bolts both massivley failed and instantly.

The bluing bothers me, its not as bad as Ive seen but its bad.

In closing this thought process, please dont stop or think Ive mad a final decision on anything, far from it, I know more and more possiblities and some things I just didnt think of before this thread was posted.

THAT was part of the goal....

Keep it coming....

Thanks

Chris and Dave

I am uploading pics right now, if there is anything you think seeing would be helpful that isnt show please ask away and Ill shoot it.....and upload it.


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Originally Posted by Alan Roehrich

Drooze,
Valve contact with a piston won't cause "peening" of a bearing, nor bluing of a crank or a rod. The valve contact came when the piston got loose from the crank. You have two instances of piston to valve contact on one piston. That tells you it was coming loose once and there was minor contact. In order to hurt a rod or a rod bearing, the contact with the valve would have to be severe enough to do massive valvetrain damage, either in one location, or spread over an area.


You had a failure in #3 rod, not in the valvetrain. Period. Either the rod bolts failed because they were either over stressed or not fully preloaded, or the rod got out of round and grabbed the crank and it failed the bolts. Bluing is one of two things, poor lubrication, or a rod bore out of round. The only other possibility, and it is rare, is a crack in the crank, which, by the way causes the journal to be out of round, and usually causes an oil pressure leak.

One other possibility is the wrist pin seizing in the piston, that will either pull the rod throw out of the crank, pull the wrist pin out of the piston, or pull the rod off of the crank. It will be obvious if the wrist pin was seized.

If you've ever seen a timing chain system work, you'll know that what you're describing is nearly impossible. Timing chains don't work that way, and harmonics won't make them work that way.

You are free to believe as you wish, the parts, money, and time belong to you and your father. I've been doing this for 30 years, and Adger has been doing this about as long as I've been alive, that makes for about 80 years of combined experience, and it looks to me like neither of us feel your explanation is plausible.