Quote:
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....
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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.