406 Finally gave up, new build coming
 

Last weekend, I was as I was accelerating up an off ramp in second gear I decided to jump on the gas for fun and as soon as I hit it the crank snapped in two towards the front of the engine. The engine kept running but it vibrated badly and was leaking oil from the balancer seal. I have not taken it apart yet but the balancer wobbles up and down at least 1/2 an inch. I limped it home 10 miles and by the time I was home the oil pressure had dropped 20 LBS and the oil temperature had climbed 20 degrees. My gut feeling is the crank snapped between the #1 and #2 main bearings but the broken pieces are staying engaged enough to keep the car running. I will have to take it out and survey the damage.

No matter what the outcome is I see a new 434 on the way!!

Bummer but it sounds like you've got it taken care of :cheers:

Already have an idea on build specs?

Bummer. My car is running really good, I'm afaraid its about to break something also.:ack:

10's for sure. At least it happened right before off season and not during summer

...and drove it home for 10 miles? That's amazing it kept going.

GEEEEZ. Good thing you made it home. It sounded great not that long ago.

I guess some things are just meant to be.:D

Good luck with the new one.

It sounded good right up to the big bang sound! I have a feeling the spun balancer and detonation issue related to the spun balancer contributed to the crank failure. I suppose the 1000 or so 1/4 mile runs and 200 plus dyno runs didn't do it any favors either.

For seven years I beat the tar out of this engine and it finally gave up. Oh well I am not disappointed because now it gives me an opportunity to play with a new combination.

Sounds like you got your monies worth out of the 406! 1000 runs is alot! Well this gives you an excuse to move on to a bigger and potentially better engine. Good luck with the new build.

I'm sorry to read about your engine failure but I like seeing that you've kept a positive mental attitude over the whole thing.

We could all learn from this though.

You know what would be of GREAT BENEFIT? The autopsy results.

If you would post all the parts, specs and what you find once you take apart the engine it would greatly help those in their next engine build.

I see many posts about valve train failures, spun brearings, etc. but too seldom do I see a listing of the parts involved, the clearances, the probable cause, etc. It would help in future discussions about cast Vs forged cranks, different brands of both rotating and recirprocating parts, balancers, etc.

All that may well help prevent others, including me, from experiencing the same thing.

Just my suggestion.

Jake

Gee, I noticed where Brian already posted the probable cause. He had a thread explaining what happed with his balancer (and what brand it was). It's in a recent thread of his. (I know you do well with the search function, Jake. ;))

Brian,,,that's too bad. Hopefully, you're as motivated to do a new motor as you sound. I'm also surprised you made it the 10m back home. Sounds like you used good stuff -- besides that balancer.

:thumbs:

Well Brain started the build yet?

Sorry to hear the old motor gave up but eager to hear what the new build is! :lurk:

I have not even pulled the engine out yet. I have been concentrating on my 555 rebuild in my real drag car.

I will get to the 406 in December.

Brian

Let me know if you want any help wrenching on it. I got mine back running.