DP #24 Engine failure....

[Chris "drooze" Wertman]

Ok, so I feel compelled to post this #1 for many other DP Owners out there, Ma Mopar, and Gary Stanton as well as several component vendors while I may never be a fan of I would have bet just about anything their issues caused ours.

These were not the cases.

The circumstances of the failure were as follows.
The car came out of the water at 8000 rpm give or take. My issue for lack of a burnout limiter.
It freespun, no load.
Rods exited the pan.
We were having issues with oil pressure or so we may have thought, we are still unsure about the sender / gauge combo.
We had a 3 quart accumulator in place and functioning correctly.

We took apart #24 DOA Engine #2 Here is what we found.

#3 Smacked an Exhaust valve HARD
Minor/Minimal scoring to the journal on #3 (dono about #4 will have to cut that one off)
Some bluing to #3 rod. top half
NO Breakage of Rod, or cap, both intact.
Bolts both broke at mating surface.
#4 Rod Z'd from the impact of the #3 Rod and Wristpin exiting the engine in castaspophic fasion. (a very intersting sight, it looks like it was made that way) and 100% intact. just well z'd to the wrong journal.
The rest of the engine internals took massive damage as it looks like (as in we cant find and there is a lot of metal unaccounted for the wrist pin of #3) shattered or was scattered around everywhere.
It appears the bolts sheared on #3 the assmebly broke free of the crank, on a subseqent rotation, (from the side scar on the crank) the crank smacked the rod from the side, and disloged the pin from the bottom of the piston.

All rest of the engine journals and bearings looked as would be expected on an engine that had full oil flow and only 6 or 7 passes, excellent to just like they should, no galling, no scoring, no oddities of any sort, Id run em again in an instant....that nice.

No damage (visible) to cam other than a bent pin. Billet Gundrilled cam, being sent back to manufacturer to be checked for microcracks/straighness and suitablity to be run again.

Someone who was present called before I tore the heads off and said "Ive thought about it an I think you smacked that valve hard and things went bad from there" I thought about it and I agreed maybe...

After much thought and discussion here is OUR , Me and the Old Mans conculsion. With someones initial and correct call (I would mention their name but I didnt ask them if I could)

The smack on #3 at 8000 (or where ever it happened below that) set things in motion as was suggested.

Cam backlash is where I come up, we are not using a stock chain but a double roller, and there is much more play in it than a "fresh" setup, the follower/tensioner design is adequate but was designed for street use, even in the aftermarket setup we are using, when the bottom freespun it backlasked on a very heavy (and ours is 4 lbs lighter than stock) cam, that allowed the tensioner (which its design would allow) to collapse from a ) to a ! this would allow the cam to retard by at least 6 degrees and the exhaust valve made contact. We have a very significant duration and VERY agressive ramp rates.

Clay testing on the engine prior showed adequate not even "marginal" on both in and ex at the advance I was running (4 deg) So...

The springs have a killer rate and pressure and weve had no issues nor has anyone else with them over 8500....

So this conlcusion seems to be the appropriate one.

The Rods (scat) I am actually VERY suprised that any I beam forged rod made in China took....its staggering. They are mutilated but intact not broken.

The workmanship of the assembly in the case of our bottom end, no issues clearances etc all looked to be spot on.

The bolts, well they failed but under the circumstances, I dont know that any wouldnt have.

The timing set and I wont name the vendor is the ONLY item I can look to.....there is a significant lack of availablity and choices for these engines many others with different combos dont have to deal with , that will change but for right now well....were "stuck" short of a custom setup. As well not even the timing set itself but the multi plate ) shaped tesioner that could collpse to a full flat condition, this is both the original and aftermarket design.

These are the things we saw, these are the things we did and these are the conclusions we have come to.

I post them here so as to alleviate any "finger pointing" or "uncertainty"

Some of which I may have caused by what I have said and not said.

I thought the rod gave, and well, I was wrong, it and the cap are intact. bolts broke and the rest was haging through the pan.

And I thought as did my father we had oiling issues, or the potential for them, this was incorrect as well from the clear evidence shown in the engine.

Pictures to follow as we upload them after I get on the road to Houston
Ill put Mandie in Charge of that

The reason it took so long ? Well , weve been busier than you can imagine re-rigging the trailer, broken truck, new engines, and business. So....here it it.....sorry it took so long, I know of one engine guy who has been loving our failures (the engine guy many are sending their DP motors too)

Cheers all

Have a safe and happy easter......

[Alan Roehrich]

If you had a timing chain problem, odds are you would not have one bent valve, but rather eight, or maybe even sixteen.

It is VERY rare for a bent valve to bend a rod, break a piston, or kill a wrist pin.

Bluing of the journal, the bearing, or the rod is a sign of a lubrication problem, and/or a problem with the rod staying round.

Excessive RPM, especially in a burnout, will often over stress the rods, especially on the exhaust stroke where there is little or no resistance to upward piston motion, and only the rod stops it. When a rod bolt shears, it is usually a sign that the bolt was not properly preloaded.

I've never seen a need to spin an engine past 5K in a burnout. I count it as I'm doing a very poor job of driving if I even hit the burnout chip I usually set at 5500.

[GTX JOHN]

Exactly Right: Alan I would kick the my boys b*tts if I played the run back over 5,500 on burnout

[Chris "drooze" Wertman]

Not being "contrary" or arguing just explaining why how what we came to our conclusions.

If you had a timing chain problem, odds are you would not have one bent valve, but rather eight, or maybe even sixteen.

I didnt say it broke I said I believe it backlashed when it freespun this would generally ONLY affect 1 valve , and not even neccesarily 1 , depending on where in the roatation occured.

It is VERY rare for a bent valve to bend a rod, break a piston, or kill a wrist pin.

I didnt say the valve bent, I said it tapped, and our pockets are dead on anglewise and 3/4 the diamater of the valve face. The valve is not bent or stuck (there may be minor runount now of course) but its not "bent" as in at issue. When it contacted as is evident by the very clear impression on the cylinder it was very near tdc, unlike the other and prior valve hit that it with a "hung" valve where the valve did bend and the mark was nearly an inch off.

Nor did I say, or mean to infer a valve broke things, rather the peening of the bearing on the crank started issues which escalated from there.

I said or thought I said, the rod was bent on #4 by the exit of #3, the wrist pin kill and piston issue was caused by the crank shearing the hung rod on a Subsequent roatation while the piston was low in the bore, there is also evidence of this on the bottom of the piston , the crank and the rod.

Bluing of the journal, the bearing, or the rod is a sign of a lubrication problem, and/or a problem with the rod staying round.

Correct, which comes first though ? The chicken or the egg ? In this case we think the smack on the bearing caused by the hard valve tap started what ended up with either the bearing getting peened against the crank,

And there are absolutley no other signs anywhere in the engine of lubrication issues, we were pretty sure we would see them, we my father especially was very suprised not only not to but to see things as well as they were everywhere else.

So, explain why ONLY on the rod where the valve smacked, is there evidence of bluing and perfectly in pocket the tap is (on other engines if it had occured after the rod broke its not usually perfeclty in line with where it should be)

Im being serious and not a dikk , I am curious as to alternative explanations to why on #3 where the valve hit, all the other damage would be centered. and when its pretty clear that #3 hit at TDC or close , we are talking a very small amount, the only thing I can see to account for this would be backlash, OR its possible that the whole debacle was perfectly timed and the rod broke first causing the rod to be propelled upward with the assembly at the exact time the exhaust valve was only say 100 down and the mark was a marvelous coincidence of timing ? Or is it more likley the cam fell slightly retarded in relation to the crank for a moment and this started things in motion ?

If there was no binding or galling of rockers, guides, no bent valve, nothing else and adequate ptv clearance, and no other taps, how else can this be accounted for ?

Excessive RPM, especially in a burnout, will often over stress the rods, especially on the exhaust stroke where there is little or no resistance to upward piston motion, and only the rod stops it.

Agreed.

When a rod bolt shears, it is usually a sign that the bolt was not properly preloaded.

Thats incorrect, In this case, I saw it done on this engine at Stantons facility in person on this engine.

I've never seen a need to spin an engine past 5K in a burnout. I count it as I'm doing a very poor job of driving if I even hit the burnout chip I usually set at 5500

Really only second time in a car ? And at that in a FI car with the setup we have ? It wasnt intentional of course you are correct in that there wasnt a need. Hmmmm.... I wouldnt and it wasnt me driving so. The engine will go from pretty much nothing to 8k at 55% tp in the water. Instantly. So I should have seen it and do as my failure for not anticipating someone else , and we did set the car up for multiple drivers, my fault for not anticipating the need for one. Not the drivers in a NEW and wholly different setup than they are used to.

[sst1988]

Sorry to hear about your mishap......

[Adger Smith]

Roller Chains don't work that way. The slack was probably caused by something wrong in the valve train making it go going harmonic.
Pick something else to blame.
I don't like revs in a free spin too high for the weight/strength ratio of the parts. That usually separates the valve train and makes it unstable, hence loose chain... There is probably other damage in the valve train you havent seen.
I've never seen a valve hitting a piston long enough to blue a rod/rod journal and loose a bearing. Valve head usually breaks off at the valve stem first.
ditto:
On lubrication or pulling the rod out of round. A long time ago.. close to the time you were born. Big block chevies had problems with rod bearings being too tight on the journal at the parting line and when the revs went high they pinched the crank and wiped all the lube off and caused the rod to fail/spin the bearing. I've seen a lot of that in the early days of my business.
I made some good money fixing them where they would last. It would be interesting to do an inspection of the pieces.

Another thing that makes rod bolts fail is excess load by negative G-forces on the piston-Rod assy. To put it bluntly the piston and rod trying to launch into orbit on the Ex stroke with no load. Resulting in a load that is too much for the strength of the bolt. Condition of the parts could determin if this was the case. Also if the burnt/blue of the rod extends into the bolts the heat could have weakend the bolt lowering it's strength and it's yeild point.
Just my .02

[Rich Biebel]

What gear are you doing burnouts in?....

Use high gear or start in second and quickly shift to high and watch the tach closely..........Starting in low allows the engine to rev much too quickly....,

No need to do a burnout anymore than 500rpm over converter stall

Trying to determine what broke in a major engine blowup is difficult.

If it had spun a bearing it would be easier to diagnose.......but any blueing of the crank or rod has me thinking that is where the event started....

Suffice it to say 8000+ rpm is to high. Any contact between the piston and the valve is enough to start a catastrophic failure.......

Without testing how do you know your engines rpm limits? It is much better and safer to approach that from a conservative side....


Small block Chevs are known for being able to spin very high with ease......Stock solid lifter small blocks could go to 8000rpm or higher.......BUT they did not make power there and they usually broke within a short number of runs at that kind of rpms without many parts upgrades....

[Chris "drooze" Wertman]

Originally Posted by Rich Biebel

What gear are you doing burnouts in?....

Use high gear or start in second and quickly shift to high and watch the tach closely..........Starting in low allows the engine to rev much too quickly....,

No need to do a burnout anymore than 500rpm over converter stall

Trying to determine what broke in a major engine blowup is difficult.

If it had spun a bearing it would be easier to diagnose.......but any blueing of the crank or rod has me thinking that is where the event started....

Suffice it to say 8000+ rpm is to high. Any contact between the piston and the valve is enough to start a catastophic failure.......

Without testing how do you know your engines rpm limits? It is much better and safer to approach that from a conservative side....


Small block Chevs are known for being able to spin very high with ease......Stock solid lifter small blocks could go to 8000rpm or higher.......BUT they did not make power there and they usually broke within a short number of runs at that kind of rpms without many parts upgrades....

Burnouts in 2nd and then 3rd as you said. The "target" was 5000-5500 (stall is right around 5200) so yep on target there. The issue was it went to high, that was not intentional.

Now that being said I would agree 100% its difficult to diagnose exactly where it started, that being known the reason for my post was the following

For many of the DP Owners we are in contact with, but its easier to put it here and on the blog than repeat the same thing 25 or 30 times to interested parties.

My plan was.

To provide facts (what we saw)
To provide observations
To provide conclusions we came to, and get feedback,

The facts are immutable, the facts are #3 rod bolts are borked.,
The rods are intact , and didnt break causing the failure itself.
The bearing journals elsewhere looked excellent and didnt suffer mass oil starvation as we expected and THOUGHT we may have encountered.
The wrist pin was torn from the bottom of #3 piston, and shattereed the pieces causing a peppering thoughout the bottom end.

Now conclusions those are both subjective and subject to change...

Others and other DP teams may come to different and more accurate conclusions, hopefully if they do they will share them with us, and we will look at what we have seen and move forward reformulating our conclusions. HOPEFULLY in the end, well....we will ALL get closer to the actual event and ALL be able to learn from it.

I am not big on keeping things "secret" I joke about secret squirrel things, but other than our exact cam profiles, well there is nothing we wont share with other DP team.

So this seemed like as good a place as any to do that.

There have been some very accurate assesments on certain items here that normally I would agree with but other things others arent familiar with, valve train harmonics can be an issue on this engine, but no damage to the valve train elsewhere is present, not even a bent pushrod, the pushrods are a large moly partially tapered and well they are staunch enough to take a massive hit and break the rocker shaft pedastals without bending themselves. So I dono, it dosent mean I will discount it, it means I will in fact look where I may have not.

I appreciate all the feedback and insight, there are things here, some Ive thought of, some I havent.

I will get the pics posted as soon as possible I think they will be a big help.

I guess Phase I was share what we saw with the other DP team.
Phase II is show everyone what happened and while I know it will never be a 100% consensus perhaps its an excersise we all can learn from.

Like my dad says "Were trainable" so....let the ideas flow forth, the other DP teams and us can take what we see, hear and reformulate our conclusions.

My X once asked me and my dad why we do nothing but argue, we looked at each other shocked, I dont think wed had an "argument" in years...Its how we "think" and change our conclusions.

In as much as how do we know the limits ? Well other DP teams are running the same, Dyno testing has showed these engines stable to 8k at no issue with better springs, 72-75 with no issues, the lifters are killers....very cool for a totally stock piece. In our case we had run to 8k under load on the dyno with no issue,.

I would like to see 8 as our limit, needless to say 8k under load and 8k freespinning arent exactly the same And the 8k freespin was not intentional.

[gmonde]

what was the water temp when the failure happened???? cold seize ??? wrist pin pulled from the bottom and broken bolts ,,, gmonde

[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.