[Tim Corcoran]

I was at Norwalk in my 65 LeMans and during my first time run on Saturday in the Pro class about 400 feet from the 1/4 mark I heard a big WHAM and everything went silent. I have included some photos. Kind of a chicken and egg situation tell me what you think went first the crack in the number 3 main web or the crank.

[Tim Corcoran]

More pictures

Last year towed the car all the way from North Carolina and took out the trans on my first time run. This year it was my engine, something evil about Norwalk for me.

[Scarebird]

You certainly don't do things by halves!

[Half-Inch Stud]

Seems the crank broke 1st, in the rod throw underarm, then then block and CYL walls.

[sdbob]

Sorry for the problem. I'd be curious what others say. I had a friend in a 66 GTO take the front out of his 455 block at Norwalk. I think it was a mid 10 sec car( he has since passed). Crank and block were used from a ... I thought balancer ,or crank and block were used with nitrous previously by the person he bought parts from. I have a stk 455 crank in my SD. Its seen 6400 couple times in the water. I'm not making power you are though.

[johnta1]

WOW!
Sorry to see all of that!

Was that a stock crank?

I wonder about the hole(s) in the bore. May have locked it up and broke everything else?

Need to see if you can find the original beginning of a crack in the crank, bore or main web.

[ID67goat]

Originally Posted by Half-Inch Stud

Seems the crank broke 1st, in the rod throw underarm, then then block and CYL walls.

This is what I was thinking also….

Sorry to see this as it looks like you put some nice parts in this engine (main caps, lifter bore brace etc.)

What crank did you have in there?

[Tim Corcoran]

4.25 Ohio cast crank, when I put this engine together years ago the forgings weren't available yet. I sure wish I would have upgraded to a forged unit. The thing is, I had a warning car slowed down about .4 from what is should have been running and oil pressure seemed a little sluggish the first two runs before the one when it broke. All the bearings look good so it wasn't starving for oil.

[Richie Hoffman]

Cast crank probably let go first
I personally didn’t like the Ohio cast cranks

[Tom Vaught]

X2 on that.

Tom V.

[chiefbigb]

Bright side you have a clean slate to work off of. Are the heads damaged much

[Tim Corcoran]

Heads are fine already bought a 71 400 block from the swap meet at Norwalk going to build a 400 stroker. Block is at the machine shop getting sonic checked so I know how far I can safely bore it out. then I will get a rotating assembly from Butler.

[steve25]

I think the block let go first.
That main web crack runs right along the oil passage that runs from the oil feed hole from that main up to the Cam Bearing .

If it was not that and the Crank did let go first, then to me since the Crank let go in its center this is a clear cut example of why at a certain point the Crank needs all 8 counter weights, not just 6!

[mgarblik]

Originally Posted by steve25

I think the block let go first.
That main web crack runs right along the oil passage that runs from the oil feed hole from that main up to the Cam Bearing .

If it was not that and the Crank did let go first, then to me since the Crank let go in its center this is a clear cut example of why at a certain point the Crank needs all 8 counter weights, not just 6!

I would tend to agree with that. We cracked 3 455 blocks in a similar fashion but not catastrophic damage because the crankshaft didn't break. We broke all 3 through the #2 main right up to the cam bore like yours. I would recommend a fully counterweighted crank of course and a slight overbalance next go. We had good luck with 2%. This is one reason the IA 2 blocks have a downsized oil feed hole from the cam tunnel to the mains. That adds a little material in that critical area. Also the solid lifter area helps hold everything together. Do you happen to know your bob weight off hand/? Curious how heavy the assembly was. Sorry about all the damage you have there.

[Don 79 TA]

good gawd those photos hurt so much to look at, especially now at this high costs of parts/labor
the price of a new engine now is just insane
i'd love another engine, but at my age, and use of the car, and then seeing the $$ needed, OMG
good luck, but...... now you can build something bigger, stronger, faster lol
that was my moto when i was doing my jetski engines lol
sounds like you did get some good life out of your setup, so thats good

[Jay S]

That is a bummer Tim. At least it happened somewhere that you didn’t end up going for a ride and it sounds like it was all contained in the engine, and you saved the top end.

From the photos the block looks like a clean break that just happened. The crack on the crank at the front side of the throw looks like it has some fatigue cracks starting. Those overseas cast cranks don’t have a great reputation anyway, and are known to break every once and a while. It very likely started a crank on one of the sides of that throw that completely broke off..

That throw further back in the engine seems to be were Pontiac cranks break when you run aftermarket balancers. Guessing this engine does not have the stock dampener. Stock balancers seem to break the crank further forward when they have trouble. The better balancer apparently moves the more severe harmonics further back on the crank.

I know people are tempted to reuse the harmonic balance when it looks ok after something like this. I learned the hard way, after something like this the dampener goes in the iron pile no matter how it looks.

[Half-Inch Stud]

Agreed, "Sluggish Oil psi" clue put the Block split 1st, then Crank.

[Tom Vaught]

Most of the failures on the 455 engine mains I have seen were at the #2 Main bulkhead,
This was at the #3 Main bulkhead I believe. Suspect a crank failure caused the block/ engine damage.

Tom V.

[Tim Corcoran]

The two runs prior to the run when the engine broke the times were down .3 to .4 where it should have been running and the oil pressure seemed lazy to come up and was lower than normal at hot idle. This is the reason I think the crack down the #3 main was already there for a while and just getting worse but I am no authority just what I think. What is interesting is the bearing on the rods looked like new and the mains all looked pretty nice too. This was a low RPM motor I shifted at 5600 and went through the traps at around 5800. This engine started out as a low 12 second street car in 1986 and evolved into a low 10 second race car. Freshened up a few times over the years this was the third crank third set of heads and third cam but the same pistons and rods from 1986. I don't feel too bad this engine served me well thousands of street miles and hundreds of 1/4 mile and 1/8th mile runs over the years.

[Jim Moshier]

WOW! Sorry to see all of this Tim!