what does this mean? i know what it is kindoff, but what does it entail, what all do you do? how much does it cost? if you do go ahead and do that can you run a supercharger without worrys?
thanks

 

Forged parts have an advantage over a cast part due to the fact that compression is involved in the manufacturing process. Thus the parts are plastically deformed and can take higher loading and such before failure.

'Forged internals' refers to the reciprocating assembly:
The crankshaft
The rods
The pistons

For a (stock) LT1 application.....strength/reliability is in this order:
-LT1 Cranks are normally fine for horsepower under 600 rear wheel HP.
-PM rods have been said to handle ~500 RWHP
-Stock pistons will NOT tolerate detonation. 6-8 psi.

A forged-dished piston will allow you to run a decent amount of boost without exceeding the limits of the factory rods and pistons.

 

When people talk about forged internals, they are really referring to three basic parts:

1. Pistons
2. Rods
3. Crankshaft

The difference between forged and cast parts is, at it's most basic, simple:

a) Cast parts are made by pouring molten metal into a mold.

b) Forged parts are made by forcing metal into a particular shape with pressure.


The two process create parts that have many differences, but for this discussion there are two important differences:

1) When cast parts reach their limits they tend to break. When forged parts reach their limits they tend to deform.

2) The limits of forged parts are generally higher than the limits of cast parts.



The reason people tell you to run forged internals for higher power applications is because, due to their nature; forged parts can take more abuse before failing. Furthermore, when they do fail they tend to do so in a far less catastrophic manner.

 

You will still need a good tune to prevent detonation; also called knock or ping. Detonation can destroy cast or forged parts, it just takes a little longer with forged parts.

 

WRT the parts in question, you also have to consider that the materials used for making forgings and castings are different. In general, the forging are stronger. There are newer technologies like powdered metal "castings" used for the stock rods that don't fit into this schema though.

As far as use with a blower, pistons are the key here. A good set of forged pistons are much more tolerate of detonation than stock pistons, and putting in a new set of pistons also allows you to lower the CR, which is itself a key to making a blower car live.

Rich

 

Speaking of which, have you seen the Oct Super Chevy yet?

 

No, worth looking at, I assume?

Rich

 

Well, they do have an article on the subject; which is mostly about the manufacturing process with a wee bit of theory thrown in.
I thought you might find it interesting, although I doubt it'll tell you anything you don't already know.

 

ok thanks, if i got just some forged pistons, would i have a better chance of my engine surviving? if so what do you guys suggest i get?

 

Cast<Forged<Billet

 

There are many good piston brands. My own preference is JE. You want to be sure to get a piston specifically designed for forced induction. This involves a thicker ring land and thicker crown as well as the dome volume needed for your desired CR..

Rich

Rich

 

This is what I did due to a tight budget. I had some dished JE/SRP forged pistons installed on the stock rods (stock bore, honed) with ARP bolts for the rods and mains. This gave me close to 9:1 compression ratio. Depending on the condition of the cylinders you may choose to bore them and use the appropriate size piston. This will add machine cost. I could get away with stock bore because my engine had only 35K miles (fair shape).

At this point you shouldn't have to worry about ring lands or any other piston failure due to detonation. The next thing to look at is the connecting rods. I chose to re-use the stockers with ARP bolts. With connecting rods you have to take into account the RPM of the application. Rods have some of the greatest loads on them while in tension...at TDC, when the inertia of the piston and pulling from the crank are in opposite directions. With this in mind, maybe 6000 RPM and 500rear wheel horse power are the limit (just my opinion). The stock crank can take that with out any problems.

So my rotating build cost was around $1200 (stock bore SRP pistons/rings pressed pin, ARP hardware, hot tank block, freeze plugs, all bearings, honing, and what ever labor). I did the assembly myself.

I dont feel I'm pushing this engine very hard with 5psi and 5500rpm shifts. I would feel safe with 10 psi and 6100rpm (considering my cam) which might equate to 500RWHP.

Do a bit of research and get in touch with a decent engine builder/machine shop.

Hope any of this helped.

-Scott.

 

never heard of billet cept for like a billet flywheel(i have) whats the dif from that and forged? hmmmm never heard of that metal for engine parts rly...

cory

 

thanks boosted for the info, ya it helped.

 

A forged crank begins as a roughly finished piece of steel in a shape looks a lot like a crank and is "pressed" into final shape.

A billet crank starts with a forged cylinder and the crank is "carved" out of it.