Eagle crank claims another victim

[SSG_Karg]

Web site under construction

Just call Rod, stand up guy.

 

[nm9stheham]

so are you thinking the cranks integrity was compromised by the balancing ,because that seems like it makes sense by that photo

Not the balancing per se, but the design of the balancing and how it works out with that particular casting. That hole is there for balance reasons and is pretty big; the long stroke forces it to be bigger for balance reasons. So the casting section is thinned out there a lot as a result. The 340 forged cranks had the same hole drilled, and for the same reason, but it was not as large and the whole crank around that area was thicker and had better slopes and strength in the area around that hole.

 

[famous bob]

Not the balancing per se, but the design of the balancing and how it works out with that particular casting. That hole is there for balance reasons and is pretty big; the long stroke forces it to be bigger for balance reasons. So the casting section is thinned out there a lot as a result. The 340 forged cranks had the same hole drilled, and for the same reason, but it was not as large and the whole crank around that area was thicker and had better slopes and strength in the area around that hole.

bottom line, go forged !

 

[jimjimjimmy]

I have been thinking scat 4" for my 340 sixpack next year nothing cazy ported procomps, 490 hp or so 4speed with 275/50/15 nittos...what do you think.should I worry about it strength for that set up

I run a scat cast 4'' 530 hp plus a few 200 hits through the years not one bit concerned .

 

[moper]

Only eagle is the problem. Scat is a great crank.

 

[K.O. SWINGER]

I run a scat cast 4'' 530 hp plus a 200 shot 8 years and not one bit concerned .

wow jimmy that would put your torque over 700 ftp ..give her the spurs. lol

 

[rumblefish360]

Sometimes forged cranks break too. 340 forged.

And how hard were you pushing it?
What was the hp level?
Auto or 4spd?

 

[jimjimjimmy]

wow jimmy that would put your torque over 700 ftp ..give her the spurs. lol[/QUOT



if you ease it on over 1.5 to 2 sec it really helps save the engine .

 

[RAMM]

I've run the SCAT 9000 cast to 649HP and no issues. I remember eavesdropping on Jon Kaase and he was saying that a cast crank will make more HP than forged because they are stiffer--he's right. The trick is staying below the failure limit. J.Rob

 

[jimjimjimmy]

I've run the SCAT 9000 cast to 649HP and no issues. I remember eavesdropping on Jon Kaase and he was saying that a cast crank will make more HP than forged because they are stiffer--he's right. The trick is staying below the failure limit. J.Rob

RAMM I think a good balance job really adds longevity to a high hp cast crank build . what you say about stiffness of the cast crank is very interesting maybe that's why they snap when they reach their limit they don't flex to absorb the stress or am I over thinking this

 

[Bad Sport]

what you say about stiffness of the cast crank is very interesting maybe that's why they snap when they reach their limit they don't flex to absorb the stress or am I over thinking this

That's what I got from it too.

 

[fratzog lover]

RAMM I think a good balance job really adds longevity to a high hp cast crank build .

And being the lucky guy who gets one of the cranks with zero porosity issues helps too!

 

[nm9stheham]

RAMM I think a good balance job really adds longevity to a high hp cast crank build . what you say about stiffness of the cast crank is very interesting maybe that's why they snap when they reach their limit they don't flex to absorb the stress or am I over thinking this

Stiffness and brittleness USUALLY go together but it is really dependent on the materials. What is wanted in this use is a materials property called 'toughness' (Yes, that is real materials term...). The materials used in a forging are quite different than a casting; the forged crank material HAS to be able to withstand a lot of distortion, because the forging process involves literally 'pushing' the material around in some areas to get it into the final shape and it gets a crapload of force and movement going on within portions of the original casting. So the forged crank materials would seem to NEED to possess better toughness to even survive the forging process alone.

 

[nm9stheham]

I've run the SCAT 9000 cast to 649HP and no issues. I remember eavesdropping on Jon Kaase and he was saying that a cast crank will make more HP than forged because they are stiffer--he's right. The trick is staying below the failure limit. J.Rob

More HP with a cast crank? I am more prone to think that the lighter weight of the casting would put more HP out of the crank as you accelerate up in RPM's....IF you use lighter pistons and rods to match the lighter cast crank. I can't quite see where the casting not flexing as much (if indeed it does not flex as much) would make more HP....If the crank flexed a bit under the load from the rods, then that lost motion and energy would eventually come back into the crank output as the rod pressure dropped.

 

[nm9stheham]

And being the lucky guy who gets one of the cranks with zero porosity issues helps too!

Luck of the draw.... This reminds me of when a cast front spindle snapped in a race.... thank goodness it was in a really slow section! We found a nice little 'cave' in the casting where it broke. Too bad I did not pay attention to that 'thing' that looked like a crack when I serviced it a coupla days before but managed to convince myself that it was a 'scratch' LOL