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....