Crank failure!

gbak

Well-known member
Joined
Mar 24, 2008
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I was wrong when I said that only the fluiddamper was damaged!
I thought from the beginning that it only was the key that was broken but this is not the case.
The crank snout is badly damaged and the snout is conical.
It seems like the damper have wiggeld more and more.
And have now ended into a disaster.
This was one of the few parts that I reused from the old engine when building the new one.

Outer diameter is 1.210 and 1/2" in the diameter is 1.238.
I could only check the dim with a dial calliper but it was enough.

A bit of the key for the timing chain wheel was also cut, as it was sticking out 1/4" outside the timing wheel flange and into the damper.

Can the crank be saved with some sleeve or so or is it just to throw it in the river Nile?


What a wounderful start of this summer, my vacation starts in two weeks!
 
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I would call Eagle and see what they say. If you need a new crank and they don't comp you, get a Scat crank this time. I would not weld it up.

P.S....I've only seen that happen once before, on a customers supercharged '78 'Vette.
 
I think I remember you bought a cast crank ??? If Eagle is really nice to you they'll send you a free crank ($200 value)... the labor is on you.... that really sux.... the assembly needs to be balanced too....might as well get a forged crank this time.....
 
I mailed Eagle yesterday and told them about this issue.
Haven't got any answer yet.

When installing the balancer I remember I did use the center screw to press the balancer on the snout.
So by that time I had press fit, not hard, but at least it was a light or middle press fit.
I also built a small removal tool to get the balanser of the crank, cause it was sitting hard.
This shouldn't happen unless something is wrong somewhere, bad hardening or bad grinding of the snout.....??
When measuring the balancer, it still seems to be ok, so the crank have taken all the damage, not the balancer!
 
Assuming the threads in the crank are good/decent, I would get a press on tool and a new balancer in place, and locktite red with the bolt, and get done with it....I have some damaged threads in my crank nose also....been that way for some 12 years....learned the hard way on a SBC to not use the bolt for pressing the balancer on.....bolt too small...for 1/2 inch of damaged surface out of some 4" of total surface, long as the key slot is clean, I would go for it, and never give it a second thought....

:quote:
 
Gene:
The total length where the balancer fits is approx 1" and I guess that 3/4" of it is more or less damaged.

One way that might?? work is to:
Remove the crank and turn the snout down, to lets say 1.210-1.215.
And then manufactur a thin sleeve in hardened steel.
Bond the sleeve on the snout with permanent Loctite.
After that open up the key slot.

If this would work I still could use the crank, and the balancing should still be good.

Theoretical this could work, but in the real world I'm not shure.....
 
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Gene:
The total length where the balancer fits is approx 1" and I guess that 3/4" of it is more or less damaged.

One way that might?? work is to:
Remove the crank and turn the snout down, to lets say 1.210-1.215.
And then manufactur a thin sleeve in hardened steel.
Bond the sleeve on the snout with permanent Loctite.
After that open up the key slot.

If this would work I still could use the crank, and the balancing should still be good.

Theoretical this could work, but in the real world I'm not shure.....

Antique engines are sometimes saved this way. The crank is ground down, a hardened sleeve is heated and shrunk on, and the crank reground. Of course, they don't see 7,000 RPM either.
 
Gene:
The total length where the balancer fits is approx 1" and I guess that 3/4" of it is more or less damaged.

One way that might?? work is to:
Remove the crank and turn the snout down, to lets say 1.210-1.215.
And then manufactur a thin sleeve in hardened steel.
Bond the sleeve on the snout with permanent Loctite.
After that open up the key slot.

If this would work I still could use the crank, and the balancing should still be good.

Theoretical this could work, but in the real world I'm not shure.....

My mammory that damn bad?? thought there was some~4" of crank from the end to the chain gear....and maybe 4.5" of balancer sleeve and it does not set flush with end of crank when home all the way....

:surrender:
 
I'd think they should give you credit on the crank, and if you have to get another I'd recommend one with a BB snout, since you need the balancer anyway..
 
This crank faliure will take me month to fix!
Lifting the engine out of the car, ordering new parts, having the new assy installed and checking the block for clereance, rebalancing the new assy and then installing everything again.
I get tired just thinking of doing all that work .......again!

No crusing/driving this summer.
I have to do the work in the coming fall/winter.
 
Hi Gbak,
Have you considered to have the damaged part repaired by "spray-metal"? Such a process is described here: http://www.gordonengland.co.uk/cws.htm
By this you can have the damage build up and remachined back to the original dimension.
I have seen this process in use at one of the local repairshops here in Denmark. Might be worth for you to investigate.
Best regards, DK.
 
Too bad you will loose this summer.

For this summer, I would be tempted to try a new regular balancer and key etc and torque the hell out of the bolt. Bmw's use a spec of 240 ft/lbs for their crank bolt, that's a bunch and if the balancer seats a little snug, but tight at the back against the crank, then I doubt it would be loose. Doubt if you could do much more damage as long as it doesn't fly off completely.

Might at least be enough for lower rpm cruising this summer.

Good luck.
 
Good idea Dk!

I just called a machine shop nearby and they thought it would be possible to spray the crank with metal a then grind it to press fit.

They have done this with crank journals with sucsess, but never a crank snout.
The guy I talked to thought this could work.
I guess that the material will not be as hard as the surface was from beginning, this could maby be a problem??

Question is; if the top material of the snout needs to be hardened?
The cranks material should be ridgid and if the sprayed material is grinded to match the balancer hole, it might be good enough!

Price for this operation will be around $200.
 
Too bad you will loose this summer.

For this summer, I would be tempted to try a new regular balancer and key etc and torque the hell out of the bolt. Bmw's use a spec of 240 ft/lbs for their crank bolt, that's a bunch and if the balancer seats a little snug, but tight at the back against the crank, then I doubt it would be loose. Doubt if you could do much more damage as long as it doesn't fly off completely.

Might at least be enough for lower rpm cruising this summer.

Good luck.

I already torqued it to hell a lot of times and it somtimes worked but most of the times the damper wiggled of imidiatly.
Of course I did not have any key at all.
And the balancer was not perfect either.

Problem is that the belts will make the damper to wiggle.
Without the force from the belt it might work, but I doubt it will work with the belts from the servopump/waterpump/alternator.
 
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