lsxmini

Whats going on guys, I did some searching and couldnt find anything that directly answered this question. As it states in the title, at what point/power level is a forged crank absolutely necessary?

I never really considered this question until talking with a good friend about my current engine build. Just for some background, my build is a LM7 5.3 going for boost (either a big single or twins) with the following plans for the bottom end:

TSP 347 rotating assembly (3.903" wiseco dished pistons, TSP H-beam rods w/ARP2000 bolts, factory GM crank)- not yet purchased

ARP head and main studs- already purchased

So in telling my friend about my plans for the rotating assembly, he goes on a rant about why I need to get a forged crank instead of a factory one. His argument is based off of a few people he knows who have managed to break factory cranks under moderate power levels (500-700rwhp). From what I know, those guys were running procharged setups on true LS2s. The only sense I can make of those instances are that perhaps the added stress from driving the procharger snapped the crank, or their bottom ends were never properly balanced. But, I do not know enough about their setups to draw any conclusions.

Now from my research, on here and other sites, I've always seen guys making serious power with a factory crank on a turbo 5.3 setup. My goal is to build a bullet proof engine that can safely and reliably run at 700~800rwhp. So for my build and goals, would a forged crank be worth the money? I'm fairly confident I can reach my goals with a stock crank, but would like to be sure before I pull the trigger on a rotating assembly.

ls1charged

iTrader: (8)

if theres physical damage to your crank replace it or if your planning on making over 1500 hp

JoeNova

700-800whp is still within range of the stock internals.

The stock crank gets iffy around 1400 hp, which is about the same area that the 4-bolt OEM blocks stuggle to keep the heads sealed.

Stock block? Stock crank.

Aaron at SDPC

For what your goals are I would recommend sticking with a stock crankshaft.

redtan

iTrader: (5)

Given your choice of boost (eg. turbos) and desired power levels you will be fine with a nice Gen IV crank especially if you keep the RPMs relatively low.

Although depending on how much you have to pay for a stock crank you may be able to find a slightly used forged crank and only have to pay an extra couple hundred more which is not bad. But I wouldn't go out of my way to spend $800+ for a forged crank on that build.

pantera_efi

iTrader: (1)

OK, I realize the "HP" question being answered correctly.

My concern does relate, the "cost" question.

At this time I have Forged 4340 crankshafts on sale, 4.10" & 4.125".

These will be at a great price, just PM.

These are forged/manufactured in the Calles, Scat, etc. plant, the same as their "intro" class, NOT BILLET.
This crankshaft has 1850 BW, good for metal removal when balanced. ( No Mallory)

Thus if the OEM crankshaft needs a "grind", a balance with "heavy metal" AND RE-NITRATED, COST is LESS for a new crank.

What do your rods weigh ?

Lance

lsxmini

Thank you everyone for the feedback, I'll be sticking with the stock crank like originally planned.

Lance,

I appreciate the offer. Since the crank I have only needs to be polished and balanced I'll be sticking with that. It also helps that a good friend of the family is an engine builder, so costs will be minimal.