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/another-350Z-vs-43L_700455.htm

 

[92 Ty 1173]

Re: stock crank limit

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]

Re: stock crank limit

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]]

Re: stock crank limit

He probably couldn't explain this over the phone

:rotf:

 

[Quickstop [UK]]

Re: stock crank limit

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]

Re: stock crank limit

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]

Re: stock crank limit

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]

Re: stock crank limit

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!!!!!!:tdown:

 

[clone 94]

Re: stock crank limit

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]

Re: stock crank limit

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]

Re: stock crank limit

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]

Re: stock crank limit

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]

Re: stock crank limit

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]

Re: stock crank limit

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]

Re: stock crank limit

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.

 

[4.8t]

Re: stock crank limit

true. i think we are going to tune in 15psi and then back it down for street use. that way if he comes across something fast he will be set to just turn it up a bit for the race the turn it back down. we need a dyno day for this thing to see where we are at. we put in some 3.90's and a trutrac this weekend.

 

[clone 94]

Re: stock crank limit

true. i think we are going to tune in 15psi and then back it down for street use. that way if he comes across something fast he will be set to just turn it up a bit for the race the turn it back down. we need a dyno day for this thing to see where we are at. we put in some 3.90's and a trutrac this weekend.

i ran 25 psi for a very long time on my old motor, a bone stock never opened 4.3 balance shaft short block with stock vortec heads, a mild cam and a pt61

its all in the tune, if your confident you can get it spot on i wouldnt think twice about running lots of boost on these motors. i spent many hours tweeking the tune on my truck

 

[blk00z28]

Re: stock crank limit

i ran 25 psi for a very long time on my old motor, a bone stock never opened 4.3 balance shaft short block with stock vortec heads, a mild cam and a pt61

its all in the tune, if your confident you can get it spot on i wouldnt think twice about running lots of boost on these motors. i spent many hours tweeking the tune on my truck

x2, I ran 26psi on my stock motor with 50lb injectors, a pte61, 3k stall, 255 fp, and meth for a about a years time until I finally broke a ring land. And it was only on a base, get it running tune.

 

[4.8t]

Re: stock crank limit

x2, I ran 26psi on my stock motor with 50lb injectors, a pte61, 3k stall, 255 fp, and meth for a about a years time until I finally broke a ring land. And it was only on a base, get it running tune.

how much meth were you spraying? we have 60lbhr injectors which flow more like 72ish lbhr with our fuel pressure. with 13psi we are at 85% duty cycle. how big is that pte61? the way this thing runs with 13psi i would be scared at 20+psi.

 

[rdyto12]

Re: stock crank limit

May I ask you a question?

Will stock 4.3 (Bravada) heads work on a Typhoon 4.3?

Thanks,
Randy