A (forged) 340 Crank is Not a (forged) 273/318 Crank?

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340 .010/.020. cast

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3 lbs lighter than the 2 forged ones.
4 lbs lighter than my forged weighed on the same scale.
 
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d55dave said:
Forged is steel. Cast is cast iron.
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I don't think that's quite true. Look at the link Jadaharabi posted. Casting is still done with Steel. I am not a metallurgist, but iron alone does not have the strength or harness that a crankshaft requires. I believe a crankshaft needs to be steel alloy of some kind.
 
rustyswinger said:
I don't think that's quite true. Look at the link Jadaharabi posted. Casting is still done with Steel. I am not a metallurgist, but iron alone does not have the strength or harness that a crankshaft requires. I believe a crankshaft needs to be steel alloy of some kind.
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maybe not......

Since the invention of nodular cast iron in 1947,through the efforts of long time,the tensile strength increased to 600 ~ 900 mpa, approach or exceed the level of carbon steel.Compared with forging steel materials,nodular cast iron crankshaft not only has the characteristics of simple manufacture simple and low cost,but also shock absorption,abrasion resistance and is not sensitive to surface crack.

For high grade materials like QT800,QT900 for cast crankshaft,many cast crankshaft manufacturers also have done a lot of research experiments including alloying research is not all,often need to combine the size of the crankshaft and using iron mould coated sand,shell mold casting process such as filling pill to achieve together,and the molding process in the production of QT600, QT700 brand of the crankshaft and camshaft has a large number of applications,and become a development trend.
 
340 standard. forged

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My forged crank has solid throws and my cast crank has the holes. I think that's interesting.
 
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How many balance holes are drilled in each of your crankshaft counterweights? More than one? I would like to find out if the crank I pictured (see post #24) was only factory balanced or has been re-balanced since then. Thank you.
 
dibbons said:
How many balance holes are drilled in each of your crankshaft counterweights? More than one? I would like to find out if the crank I pictured (see post #24) was only factory balanced or has been re-balanced since then. Thank you.
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You're crank in post 24 looks pretty standard to me. One of my cranks has one hole in the throws and some have 3 holes in the throws.
 
Now I am thinking about aborting the re-assembly of this core 340 I purchased (with new rings and bearings), since the forged crank it came with does not have the holes drilled in the #1 and #4 connecting rod throws. I don't have a clue if the reciprocating parts (stock connecting rods and aftermarket cast pistons) are balanced correctly to this crankshaft. And I don't know anyone in the area who can balance a motor. Just to be safe, I think I will find some Baja 1000 racers and ask them who builds (and hopefully balances) their motors down here.
 
How about taking your original Rod piston wrist pin and rings and connecting rod bearing weighing them on a gram scale.
Then take your new piston Rod wrist pin rings and rod bearing and weigh them and see how close they are to the original ones.
 
yes, in order for that "lightning hole" to be possible, the crank flange is pie cut for the drill access.
 
Evidently no one in this area can balance a motor, locals referred me to Crower in San Diego, a mere 1000 miles away.
 
RustyRatRod said:
And yet most factory builds ran well in excess of 100K miles.
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Those are put together Factory family cars and muscle cars. Then people started mixing up crankshafts and putting oversize pistons in them and not balancing them and breaking things.
 
dibbons said:
How many balance holes are drilled in each of your crankshaft counterweights? More than one? I would like to find out if the crank I pictured (see post #24) was only factory balanced or has been re-balanced since then. Thank you.
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Thing is, the balance holes in the crank throws arent drilled to a drawing, they are drilled differently on each crank, depending on where it needed to have weight removed to be balanced. No two factory cranks would be the same.
 
There is a certain amount of unbalance that is acceptable in production work. 318's/forged 340s were neutral so everything was neutral balanced. 360's were externally balanced so their balancer had the weight on it. The closer you got to true neutral balance ($$) , the smoother the motor became. My 1UZFE Lexus V8 can idle with a nickle balanced on its edge on top of the intake. They also said that that line had $1B in develpoment cost. Its all in the bottom line.
 
I culled a 273 crank for use with a 340 setup and I noticed the 273 had THICK wall piston pins, I mean like DIESEL thick, to offset the lighter piston weight, I guess so they could use a 318 crank without Swiss-cheesing the counterweights!!! Couldn't really tell the difference in it and a '68 LA 318 crank, both using the skinny beam rods.
 
Hi Folks,
Real 340 cranks have a deep line cut across the second counter-balance that all the other S/B steel cranks don't have.
The undrilled rod throws is also a big giveaway too!
Any good shop will re-balance a steel crank for the heavy rods.
Most heavy rods S/B (and B/B) can be reworked on the beams and end weights to get them real close to the stock 318 rod wieghts anyways (and LY rod).

PJ
 
Another difference between 273 forged steel cranks and 340 forged steel cranks is the 273 has a smaller centering recess for the torque converter hub (67 and earlier at least). If you put a 273 crank in a 68 and newer 340 or 318 then you won’t be able to get your torque converter to bolt up. The recess can be machined I believe though to accept the larger hub on the newer torque converter.
 
STRorange said:
Hi Folks,
Real 340 cranks have a deep line cut across the second counter-balance that all the other S/B steel cranks don't have.
The undrilled rod throws is also a big giveaway too!
Any good shop will re-balance a steel crank for the heavy rods.
Most heavy rods S/B (and B/B) can be reworked on the beams and end weights to get them real close to the stock 318 rod wieghts anyways (and LY rod).

PJ
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Got any pictures of these lines?
A big give away?
 
yellow rose said:
You can have two identical cranks, that weigh the same and they will take different balance corrections. With the same bobweight.

A few degrees difference in where the counterweights are makes a big difference in balance correction.
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All of confuses me to no end. That is why I took my crank's to a good machine shop and let them balance them.
Good luck to all and thanks for the info.
 
Bighead440 said:
I culled a 273 crank for use with a 340 setup and I noticed the 273 had THICK wall piston pins, I mean like DIESEL thick, to offset the lighter piston weight, I guess so they could use a 318 crank without Swiss-cheesing the counterweights!!! Couldn't really tell the difference in it and a '68 LA 318 crank, both using the skinny beam rods.
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I have two sets pf them little skinny rods!
 
RustyRatRod said:
I have two sets pf them little skinny rods!
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Perfect for 300hp-ish builds. I have some of the (4340?) MoPar aftermarket skinny rods that I think would withstand 500'ish HP, but haven't tried them. Lightweight pistons always help longevity. Might have to massacre the crank counterweights to balance, however!!
 
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