Billet & Forged Crankshafts

[More Power]

Can anyone tell me the difference in strength & durability between billet & forged?

Thanks,

Jim

[gmctd]

Forged cranks, having the general shape of the finished product, need centering, cross drilling, do the hubs, snouts, crankpins and mains journals, and you're done, maybe some tuftriding and polishing

Billet cranks are labor intensive, being totally machined from a round bar , or billet blank, the diameter of which must be greater than the throws\counterbalances.

Would be my guess.

Now, about those billet door knobs, steering wheels and columns, mufflers, brake pedals, license plate brackets, etc...............

[Robyn]

The forging starts with an almost white hot chunk of metal and they stuff it into the forging die and the giant drop hammer comes down and smashes the metal into its finished shape.

Big, heavy and monsterous machines to do this.
The advantage is there are few stress risers left after the process.

With a billet it is as has been mentioned cut from a large chunk of round stock.
After the initial machining the unground crank needs to be stress releived in an oven at temps just almost red hot and then cooled.
This will allow the thing to settle into whatever shape it needs to be and not have any internal stresses left in it.
Once the crank is just about done the journals are nitrided and then they are done.
The nitriding /tufdriding (GM) gives the bearing surface a nice hard wear surface a couple thou thick..

We used to hard chrome the journals and grind back to spec.
If done right its tougher than the hubs of hell and will really make a nice crank.
If done wrong it peels and your toast.
Last crank we hard chromed was a 454 gasser and we underground it .005 and chomed it back .007 and then ground it to standard spec.

It ran 5 seasons in the race boat and then ended up in a pickup. Have not a clue as to where it is now.

Too many folks are using the term "Billet" for everything from door knobs to rocker arms.
Its sounds way kewl so they use it as a selling point.

I asked one of the crank companies a while back to quote me on a billet crank for the 6.5. $2600.00 plus freight to get it here.

Ballanced and ready to go as long as I sent them the goodies such as rods, pistons, ballancer and such.

Robyn

Truth is its highly over used

[ronniejoe]

The major difference is in the strength. The forging process yields preferential grain flow which improves strength (in one direction). As was mentioned, you start with a hot chunk of metal and progressively form it with dies until it is close to the final shape.

Billet (a fancy way to say machined from solid) parts are just machined from a chunk of metal. The material is homogeneous. The machining will cut across the grain, interrupting the pattern.

Depending upon how the initial chunk or material was formed, a machined from solid piece may be stronger than a cast piece, but a properly forged piece will be stronger than either.

[gmctd]

The billet piece has an added advantage - any weak points in the forged piece can be strengthened in the billet piece by leaving extra stock - this is easily seen in the aftermarket transmission shafts, where the shaft diameter is increased in critical areas, and splined areas are lengthened for more 'bite', or spline length is reduced for increased strength in the uncut diameter.

And often the billet piece is 'tempered', where the forged piece is not, or is to a lesser degree

GM offered forged crank blanks, totally un-machined, to be cut and finished by those with facilities to improve the piece, or alter stroke somewhat - also offered semi-finished pieces for minor alteration.

Be neat if the 454 blank could be machined for the 6.5, requiring also an altered camshaft.

What's the thought(s) behind your question?

[ronniejoe]

The billet piece has an added advantage - any weak points in the forged piece can be strengthened in the billet piece by leaving extra stock - this is easily seen in the aftermarket transmission shafts, where the shaft diameter is increased in critical areas, and splined areas are lengthened for more 'bite', or spline length is reduced for increased strength in the uncut diameter.

And often the billet piece is 'tempered', where the forged piece is not, or is to a lesser degree

The only reason people advertise "billet" parts is to sucker gullible folks into thinking they're getting something that they aren't. The word actually comes from the fact that large chunks of raw material are called billet...hence, "machined from billet" which has been shortened to "billet" for advertising purposes. By making a redesigned piece from solid stock (billet), one can alter sizes and gain some strength in some areas. If one were to design and make a new forging that incorporated the increased section sizes and make a part from that, it would be by far stronger.

The reason that new forgings are rarely made by the aftermarket folks who really like to use the "billet" advertising advantage is because a forging is expensive and their small production runs cannot justify it economically. In this case, a "billet" piece becomes a reasonable compromise, but it is a compromise none the less. To sell their parts, they crow about it being a "billet" piece that is "stronger than a forging" and leave the impression that forged pieces are somehow inferior. This is completely not the case.

For the subject at hand, I would be very skeptical if someone claimed that a "billet" crankshaft for the 6.5 was very much stronger than the current cast cranks that we are using.

As for your comments about tempering... What is your source for information here?

[bcbigfoot]

Can anyone tell me the difference in strength & durability between billet & forged?

Thanks,

Jim

I suspect GEP or who ever will have a HP/service life number in mind and will engineer a crank around that number. If GEP were to make a forged crank they would use a cheaper metal, if they build a billet crank it will have better metal in it to meet the engineered service requirements.

Fordged or billet isn't the issue service life is and the number that was decided on for this crank. Lets hope it is high and affordible.

[john8662]

Glad that this tread was created, finally settled some underlying questions I've had about the new rumored cranks and a custom one.

More good stuff to chat with the gear heads about here locally!

Humor is good, but stabs are not...

Testing shall continue!

J

[grape]

i think our race stuff starts life as a 10" diameter forged billet.............kinda heavy

[gmctd]

Think I'd like to try some of that billet cola, even better if they had it in 'pepper............

[More Power]

Member Hans Hauschild recently sent me the following photos of GEP's new 6.5. You can see the GEP banner behind the engine.





I was told last summer that GEP was planning to increase power from 205 to 235. Hans indicated to me that GEP is now saying 250!

Part of what I heard last summer involved forged steel crankshafts, a block girdle, cooling system mods and fuel system upgrades.

A asked an independent OEM yesterday about the new engine and the billet crankshafts. I was told "Crankshafts are being stockpiled - approx 400 to 500. The machining takes longer because of the material. The first ones are made from billet steel to run tests."

It appears from the above images that the girdle is sectioned a bit (notched) on each side to show its design.

Notice what looks like an electric fan-clutch....

It's interesting that they used 1989-95 accessory drive components, though the belt tensioner is in a non-stock location.

Some have theorized that the compression ratio has been reduced to accomodate the 250 hp rating.

More news when it becomes available....

Jim

[ronniejoe]

Using machined from solid (billet) components for testing is very common, even in the aerospace world. Large scale production usually would wind up being made from forgings.

That girdle looks very similar to the one that Andrew Ashwill made for his engine project. His was "billet", this one is cast.

[john8662]

Check out the t-stat housing, looks like it'll better accomodate DB2-type MFI injection pump, it's wide enough in appearance to hold dual stats.

Hmm...

Thanks for the pics Jim.

Pron for us Diesel heads...

J

[More Power]

Looks like intercooler plumbing on top of the engine as well...

Jim

[JoeyD]

I am glad they are still working the 6.5 but why go with a girdle when they could just design a deep skirt block?

[JohnC]

I like the polished billet oil filter...

[john8662]

I like the polished billet oil filter...

Prolly Chrome

[Hubert]

Cool!!! Glad to see new stuff and development for the future.

Just day dreaming really but I had pondered some thoughts about some type of REALLY BEEFY oil pan in conjunction with main girdle for a bolt on way of helping stiffen up things on bottom. That girdle looks pretty good. Also new pan to increase oil capacity.

I wonder if they incorporated any more or better oil cooling and or oil capacity with new bottom end "extension" ????