Ford Power Stroke Nation banner

billet rods vs Forged.

24K views 127 replies 43 participants last post by  southmike 
#1 ·
What is the difference between a forged rod and a billet rod other than the

easy to swallow forged price

and

the hard to swallow billet piece and sexiness
 
#10 ·
I went with a set of 2500$ forged rods vs billet....billet has its weak points, from what Ive read me and a lot other would prefer forged over billet....
 
#11 ·
A billet rod can sustain more cylinder pressure without fatiguing, than a forged rod, or PMR rod, in a 7.3 of course we are talking about. Given it is a smooth pressure build curve in the cylinder, and not a violent sharp one, because sharp pressure curves in a cylinder will kill even a billet rod.
 
#19 ·
Forged, when done right, is typically stronger than billet. Billet is popular because all you need is a CNC mill to form whatever you want out of it. The setup cost to forge something is huge and only pays off if you're producing mass quantities of it.
The end billet product looks cooler though, and that combined with a lot of people getting the idea that billet is stronger allows a lot of manufacturers to charge more for the billet products than the forged ones. So in the end a lot of times you're paying more for less.

Justin
 
#20 ·
Forged, when done right, is typically stronger than billet. Billet is popular because all you need is a CNC mill to form whatever you want out of it. The setup cost to forge something is huge and only pays off if you're producing mass quantities of it.
The end billet product looks cooler though, and that combined with a lot of people getting the idea that billet is stronger allows a lot of manufacturers to charge more for the billet products than the cast ones. So in the end a lot of times you're paying more for less.

Justin
I've had a couple engine builders tell me the same exact thing.
 
#24 ·
IMO "billet" and "forged" are contradicting terms and therefore a forged billet is does not make sense.

Billet (to me) means machined of a solid piece of steel or whatever material

Forged means hammered into shape.

Forged will be stronger/harder and billet will be more tolerable to flexing.

Anyway, what advantage is there to forge a shape purposely oversized and have to machine it? Besides raising the cost for no advantage.

Correct me if I am wrong.
 
#27 ·
The problem with a forged rod also comes from the act of forging. The forging process leaves an inconsistent, rough surface on the rod. This roughness creates a multitude of stress points on the rod. "If you disregard the fasteners, most failures in a connecting rod are generated from some sort of inclusion or stress riser on the surface, "It's like putting a notch in a coat hanger. When you bend it, it is going to break at the notch."




A billet rod is created by literally machining the rod out of a solid chunk of metal. The machining process creates a smooth surface that is (unless there is a problem in the manufacturing process or simply a bad design) free of surface inclusions. By avoiding the forging process altogether you have avoided a weakness, but you haven't been able to take advantage of strength by influencing the grain flow

Not that forged cant be made as strong as your run of the mill billett but billett can be made stronger than forged if the right steel and process is used such as used by your higher end perf manufacturers. Carrillo,crower,and R&R etc.
 
#28 ·
Shot peen a set of Forged rods, which is what the suppliers of high performance forged rods do and you have removed the surface stress factors.

Another thing to consider is that billet rods usually have thicker sections to compensate for being "weaker", which adds to the rotational mass and that can be a negative factor for some engine building goals.

Apples to Apples in terms of design, if the 2 rods in question have all of the same dimensions a forged rod is stronger.
 
#29 ·
All things being equal (i.e. the physical dimensions of the rod, material type, etc.) a forging will ALWAYS be stronger than a piece made froma a "billet", or from casting.

The forging process changes the internal grain structure of the piece. These "grain lines" follow the shape of the piece, making it strong.

When you cut a rod from a "billet" (a solid block of material), the grain lines in the piece all run parallel to each other. The machining process cuts through these grain lines, thus making a weaker piece (again, all things remaining the same).

Here is an example of grain structure in a forged piece, and how forging vs. machining cuts the grain lines. (Couldn't find a pic of a con-rod, but you get the idea):



The forging process DOES leave a rough suface finish, which can create "stress risers" and cause a surface-stress fracture. Shot-peening and polishing of the rod's outer surface removes most of this, which further increases the strength. Heat treating is last step in creating a hi-strength forged piece.

The problem with forging is that it is expensive, requiring dies, large presses and big heating equipment.

Cutting a piece from a solid billet is relatively inexspensive, particularly with todays modern cad-cam milling machines: throw the piece in and let the machine run it's program while you sit back and read the paper (well, maybe not that simple, lol...but you know...)

Lastly, "forged billet" is kind of a joke, IMO. Yes, you can have a billet block that has been forged instead of the more conventional roll-forming, but the machining of the piece will still cut through the grain structure of the forging, so there is little advantage to this...other than it sounds cool...
 
#30 ·
Enter what is commonly known as the "fully machined" rod. This process produces the strongest rod (gauging material strength only) by taking the best traits of the forging and billet processes and combining them. A fully machined rod starts out as a large forging (over six pounds in the case of most of Carrillo's rods) and then is machined into its final form much like a billet rod. This produces a rod that has the optimum grain structure of a forging along with the smooth exterior that you find in billet pieces. It's the best of both worlds
 
#34 ·
They'll handle 500 without doing anything to them with the proper tuning. They still won't be as strong as some of the aftermarket forged rods like Hypermax. They're not as beefy.

Now do the hypermax rods come shot-peened and polished?
Definitely shot peened, I'm sure polished too. They are also cryo'd.

Justin
 
#32 ·
Now do the hypermax rods come shot-peened and polished?
 
#35 ·
I just fined it hard to stomach the cost of 2600 american

thats a good chunk of change not to mention what the rest of the motor will cost. if your gonna spend that much on rods might as well balance the crank and get a good set of pistons and throw in a main girdle or that sexy swamps bed plate.

even with all those goodies a guy is right up there near 10k
 
#39 ·
My Hypermax rods weigh less than stock, and they should be more than capable of enduring what it would take to rip my block into pieces around them.

I believe the billet options all weigh more than the stock pieces. Some of them considerably more.

You had to have just read that the billet rod will have to be dimensionally larger than the forged rod to produce the same rod strength when equal material is used.
 
#60 ·
Maybe this will help clear things up a bit. Now here is the key with billet parts... billet parts have the CAPABILITY of being of higher strength than a forged part, it depends on what kind of steel the part is made from. A billet part is cut from a solid chunk of steel, so the material does NOT have to be forgeable. You can make parts out of superior strength materials to forging because you do not have to pick a material that is forgable.

P.S. 550hp was a year ago
 
#61 ·
Maybe this will help clear things up a bit. Now here is the key with billet parts... billet parts have the CAPABILITY of being of higher strength than a forged part, it depends on what kind of steel the part is made from. A billet part is cut from a solid chunk of steel, so the material does NOT have to be forgeable. You can make parts out of superior strength materials to forging because you do not have to pick a material that is forgable.
You need to cut your losses and walk away from this discussion.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top