Destruction of a BBC, WITH PICTURES!!!

Well, some of you know of the demise of my rockem' sockem' BBC powered green truck. Well here are the gory details for those interested.

May 15 2004 5:15pm;

Just got done installing the new racing clutch from 10,000rpm.******in Kevlar/bronze solid steel disc. 13 pound steel flywheel and lightened pressure plate. Son-of-a-bitch hooks up and scoots now!

Took off for dinner in Scottsdale, nice 30 mile drive.

11:30pm and heading for home. Absolutly no one around as far as the eye can see. I stand on it and wring it out for third gear. Gawd this is fun.

11:35pm; OH***** that sounds like a bent pushrod or something,,, Damit!

11:35pm and five seconds later; OH DOUBLE***** that pushrod sound just got worse. now it sounds like a piston.

11:35pm and ten seconds later; OH TRIPLE***** it seized?!?!?!?!


Ok your first dumb****ed question, "why didn't I just stop as soon as I heard the noise?" Well I was in the middle of an intersection trying to make a left hand turn. So I had to get out of oncoming traffic. Thats why.

Postmortem: Valve spring retainer gave up, split in half, dropped the valve and the mayhem ensued.

 

retainer:

 

!!

 

!!!!

 

!!!! VALVE HEAD

 

WOW
that is some nice scoring on the sleeve
lo ciento dude

 

!!!! COMBUSTION CHAMBER

 

My 360 looked like that, but with a "window" on the thrust side of the cylinder... OUCH!! Of course, he was doing 70+ when it let go...

That sux man.

Jay

 

From that we can tell the piston and rod are now door stop material. Gonna check the crank tomorrow and see if we can sleeve that hole. Provided the cracks don't go too far down the hole.

This was a standard bore 68 Corvette 427. Lots of compression and head work. If it's junk more cubes are in order. I have to present well for the Rod & Custom Ego Rama!

 

Scoring my**** thats some nice holes/cracks.I have seen my share of dropped valves but I have never seen a retainer split like that!!

 

OUCH! hope you can save the block & crank. Anything worth doing is worth doing to excess. Including*****ing up a good engine playing. Keep us posted.

 

EWWWWW! That is really unpleasant.

 

I was gonna suggest sleeve it, but you're way ahead of me.
Looks like maybe a new valve seat and some combustion chamber cleanup could save the head.

Does the retainer have any witness marks on it that would indicate the bottom of the rocker hitting it?
Or marks on the bottom side of the rocker?
Enough flexing on the retainer could cause it to fatigue and break.

Another one you may want to look at is if the valve lock bore has worn to the point where the retainer is coming up and the valve locks are going down in the retainer.
This one happened to me on a built Olds Rocket motor when I was using a high lift cam, 1.8/1 rockers (stock are 1.5/1).
Went to run the valves at San Fernando dragstrip and found about .125 clearance on one of the valves. Shoulda been somewhere around .006 if I remember right.
Amateur engine builder that I was I didn't check for retainer/rocker clearance and the stock retainer was hitting the high-lift rocker, rocking back and forth and the valve lock hole was getting enlarged.
A set of Isky aluminum retainers went in the next day and their smaller profile did the trick.
At the track and on the street until a rod let go....

 

damn, and double damn....

 

C9, this engine has been together since 91 and only has 5k miles or so on it. Was a drag engine for a while with a tunnel ram and Joe Hunt mag. I rescued it from its cruel fate in the Camaro and traded some labor for it. It was supposed to be built by the same folks that build the fuel/alcohol engines for Budwieser/Miss Budwieser racing boats. Given that it appeared to be well built, nicely balanced and machined. There was documentation as to the blueprinting when built. We double checked for spring bind and contact with the rocker arms and found none.

About the only thing that would cause the retainer to fail at this point in the investigation is fatigue. Go figure

 

i've never seen a block give out like that just from dropping a valve.

 

DAMN!!!!


jerry

 

sucks donut,

I'm always surprised at how thin the cylinder wall is in a "modern" motor.

cool pictures anyway

Paul

 

Yep... That*****s!

I dropped a valve in my Chevy II the first season I drove it; I am running****anium retainers, and the center of one busted right out. Luckily I was just cruisin about 25 MPH, and as soon as I heard something rattlin' I shut her down. A new piston, new valve & valve guide (and retainer & locks of course), and a little die grinder work on the chamber and she went back together!

The guys that did my heads for me wer really cool about it and didn't charge me anything for any of the Cyl Head labor, and they sold me a piston at their cost, so I wasn't too pissed.

They told me that they have installed around 10,000 of those Ti retainers and have NEVER had one fail... I told 'em that's my luck! If there's 1 bad one in 10,000, I'm sure I'll be the guy to find it!

 

[ QUOTE ]
This was a standard bore 68 Corvette 427.

[/ QUOTE ]

Double OUCH!

 

Aye chinga!

 

WOW! Man those walls look thin. Standard bore huh?

 

Bummer dude!

I'm sure it will get built bigger and better than before.
Sam.

 

The block looks like a goner to me. Do you think that can be sleeved?

 

[ QUOTE ]


About the only thing that would cause the retainer to fail at this point in the investigation is fatigue. Go figure

[/ QUOTE ]

I would have never thought there would be enough movement in a retainer to cause fatique.
But it makes sence, the forces on it are high...
Do you think its because of the force on the valve spring, or could it have been operating to close to its natural frequency?
Or did the taper of the key just split it?
I hope you can save that engine, from what you told me, it was a good one...

 

Alex,,, Yeah I am gonna say fatigue on this one. If you hold the pieces together you can see the way it just split in half. The keepers fit nicely into each half and match up to the cracks on the retainer. The keepers didn't pull through. Just enough spring pressure and possibly a weak retainer.

We are waiting to get the piston out before determining if the block is cracked too far. There is a crack on the outboard side that runs down pretty far, so long as it doesn't make it to the bottom register it can be sleeved.

I think what caused the wall to blow out like that was the valve. It snapped off and wedged between the piston and the bump for the spark plug kicking the piston up into the valley area.

Thin walled for sure, every piston is marked STD across the tops and they measured out on the money, so yeah it is a standard bore.

 

Wow, I've never seen engine destruction pictures so well done...that's a lot of damage...I'm with the person who brought up the thin piston walls...doesn't look like much meat on those bores, but as you mentioned, STD pistons. I would guess a sleeve job wouldn't be worth it? Wow. Good luck to you on your (future) rebuild.

 

[ QUOTE ]
every piston is marked STD across the tops

[/ QUOTE ]

That don't mean nuthin to me...

[ QUOTE ]
and they measured out on the money

[/ QUOTE ]

But that does!

I've seen pistons marked STD only to find out, they're STD for an engine with a different bore size!

But you measured them, so rules that out. Besides, modern blocks are so much thinner than older blocks. That's why they can't take the overbores like the old ones can...

 

ElP, if it was fatigue, look real close at the fracture surfaces of the retainer. Even use a magnifying lens to help. Look for "beach marks" which will look like successive ridges that appear like sand on the beach when the water subsides. It will be flat (relatively) and kind of smooth appearance. That is the fatigue crack zone. The final fractire overload portion will be like lava rock, very jagged and rough.

On steels, especially heat treated ones like your retainers are most likely, the fatigue zone can be kind of hard to see, especially the beach marks can be difficult to discern. But look for a transition are where the final fracture took place vs the crack propagation region.

Regardless of the cause, fatigue crack or otherwise, it*****s that it happened and hopefully you can save the crank and rest of the rotating****embly excpet that piston and rod. That crank should be forged, not cast. Hopefully also the block can be sleeved. I agree with C9, it seems the head can be saved with a new seat?

 

Yorgatron
I did way worse on a Y-block dropping a valve. The valve was sideways in the intake port and the piston and cylinder wall were just small pieces in the oil pan.
Judd