stock crank limit

[4.8t]

ok with supporting mods ie rods pistons..... what is the limit to stock crank with stock 2bolt mains with arp studs? and what does the splayed caps do for it? i'm sure its been ask a hundred times so thanks for answering. also the motor is balanced internally.

http://videos.streetfire.net/video/a...43L_700455.htm

[92 Ty 1173]

As far as the limits. Jeff says 625ish, with proper supporting stuff. Definately splay it, much stronger than 2 bolt or even factory 4 bolt. the tighter and stronger your mains are the better. If you got good money into the other internal don't cheap out with the bottom end. Get the main check and honed if need be also. And get the crank treated also. If your stocker is junk Scat has new cast cranks for @ $300 which are a higher tensile which = stronger than stock.

[4.8t]

Originally Posted by 92 Ty 1173

As far as the limits. Jeff says 625ish, with proper supporting stuff. Definately splay it, much stronger than 2 bolt or even factory 4 bolt. the tighter and stronger your mains are the better. If you got good money into the other internal don't cheap out with the bottom end. Get the main check and honed if need be also. And get the crank treated also. If your stocker is junk Scat has new cast cranks for @ $300 which are a higher tensile which = stronger than stock.

what is proper supporting stuff though? the guy at scat was a joke, we called to ask questions and he was the most unhelpful guy I've ever talked to. he said its a stock crank replacement so its not stronger than stock. then i ask about there billet crank, how much power it could hold. he told me its billet there is nothing stronger. that's all he kept saying. hey never gave me a guess or anything. i ask can it handle 700hp he said"its billet there is nothing stronger" i hung up it was irritating to listen to.

[Quickstop [UK]]

He probably couldn't explain this over the phone

[Quickstop [UK]]

Originally Posted by 4.8t

what is proper supporting stuff though?

ARP bolts
clevite main bearings
billet main caps
4 bolt splayed conversion
nitrided main crank after crank cryoed...
crank balanced plus line honing

haven't read of a broken crank on here with people running 10s...

what's your goal?

[clone 94]

broken cranks are rare. i would be willing to bet that 99% of the cranks that do break, broke because of main cap failure ie walking etc.

[NOJIMMY]

For what its worth....
I beg to differ about 'the rarity of breaking a crank"....
My old crank was nitrated, cryo'd, balanced, (etc, etc) with block filler and best parts.

Not all nitrating is "equal", by the way, as there is some evidence that it can make
a crank brittle and produce harmonics (if not done correctly).






-Larry

[Six-is-Enough]

Originally Posted by NOJIMMY

For what its worth....
I beg to differ about 'the rarity of breaking a crank"....
My old crank was nitrated, cryo'd, balanced, (etc, etc) with block filler and best parts.

Not all nitrating is "equal", by the way, as there is some evidence that it can make
a crank brittle and produce harmonics (if not done correctly).






-Larry

Ouch, that is ugly!!!!!!

[clone 94]

i guess what i should have said is that to me it seems rare that a craak would just break on its own and not because of some other reason, like cap walk etc. just because it may have happened to you doesnt mean it happens all the time also

just the way i see it

[Raist103]

I made 500 to the wheels on n/a 4.3 cranks. the weak point i have found is with srp pistons at 20-22psi.
EDIT
i do have 4 bolt mains

[THEMADTYPH00N]

Originally Posted by NOJIMMY

For what its worth....
I beg to differ about 'the rarity of breaking a crank"....
My old crank was nitrated, cryo'd, balanced, (etc, etc) with block filler and best parts.

Not all nitrating is "equal", by the way, as there is some evidence that it can make
a crank brittle and produce harmonics (if not done correctly).






-Larry

Just an observation. Looks like you have 2 bolt main caps. I'm sure that makes a big difference in keeping the crank in place vs letting it walk around.

[4.8t]

so it seems 4 bolt mains are the biggest saver of the crank. we had a goal of 500rwhp but i think we are close to that already. its pretty damn fast. we wanted 15-20psi out of the turbo. but at 13 right now it freaking moves. we want to be sure the crank can handle the 15psi. we are turning to 55-6000 rpm max.

[firstsy]

I run 22 pounds of boost on a stock block, crank, 4 bolt splayed caps, eagle rods and JE pistons. I have run 28 psi on the dyno but my vortech heads have a mild waller port job and we didnt see any gains.

[4.8t]

Originally Posted by firstsy

I run 22 pounds of boost on a stock block, crank, 4 bolt splayed caps, eagle rods and JE pistons. I have run 28 psi on the dyno but my vortech heads have a mild waller port job and we didnt see any gains.

how big is your turbo? we are using a 70mm. t70 master power turbo.

[syclone3]

Have another engine I will build soon. With splayed 4 bolts, rods, JE's. Spare set of Vortecs.
Current engine. Stayed with the 2 bolt mains. No ARP main studs. Eagles, JE's. Stock mains were good when line bore was checked. Ported stock heads that came on the truck. Old ATR cam. 60-1. If it makes 420-450whp I would be surprised on my dyno.
Don't see the stock crank having any trouble with 500. Even SBC's. To break the caps off. There are other harmonics going on. Lifting the heads and compressing water, etc. But like anything, stuff breaks when pushed and its not always easy to pinpoint the exact cause.