DP #24 Engine failure....

[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.

[art leong]

I tend to think the valve hit the piston after the problems with the rod started. Maybe the rod bolts stretched causing the hit.
If the bearing looked good but there was heat showing on the rod could side clearance have been a problem? The bearing should have been toast way before the rod showed heat.

[Chris "drooze" Wertman]

Originally Posted by art leong

I tend to think the valve hit the piston after the problems with the rod started. Maybe the rod bolts stretched causing the hit.
If the bearing looked good but there was heat showing on the rod could side clearance have been a problem? The bearing should have been toast way before the rod showed heat.

Side clearance looked good before chassis dyno....didnt look after but cant imagine that much lunch after engine dyno....looked good was checked , but I just dono, what makes 1 fail faster than another, clearance.........

The rod bolts stretchin could have cause a hit I guess, anything over 080 would have caused an exhaust hit, in the pics though, well for it to hit that square in the pocket it still had to be attached to the rod I think and it was a tdc when it happened, but streched bolts, certianly I think now, didnt before....or a shelled bearing maybe.

The force at which it hit causing the valve train damage....thats whats got me puzzled....

[gmonde]

looking over the pictures it looks as if the bolts stretched and broke and the rest is damage from rotating mass ,,in one of the pictures of the bearing halfs it looks as if one of the tangs is missing or flat(spun bearing?)(could be caught up in the damage) ,,,one thing i would check of whats left of the 7 rods and pistons is if the big ends are still round ,,maybe the rpm is taxing the bolts or the bottom half of the rod cap is just flexing egg shape ,try to retorque the bolts to see if they will turn(they shouldnt)

i hate to see that damge on all the hard work and money that go's into this stuff

just my 2 cents gmonde

[art leong]

I think the rod bolt failure is the cause. Thats a heavy piston and rod. And when they change direction on the end of the exhaust stroke. There is a lot of force to make the change.

Hang in there,

Good Luck

[Rich Biebel]

If you ran the engine to 8000 on the dyno.......I would have to ask if the HP and TQ was still near peak or at peak........Those numbers would indicate if the valvetrain was still stable or going into valve float. What kind of lifters do these engines use? I am sure they are rollers but are they solid rollers or hydrualic rollers? Was the engine looked over carefully after the dyno session? A valvetrain exam and an oil filter cut open and checked? Just some questions here nothing else.

I have seen engines run on a dyno that had an issue during testing and that engine failed soon after it was raced......Not saying that's what happened here but it's just a thought......

How heavy are the pistons and pins in one of these engines? I don't have a real warm and fuzzy feeling about spinning an engine to 8000+ with import I beam rods in it......I would at the very least replace the bolts with the best I could find.......