[slowbird]

I keep seeing post stating that the forged cranks that are currently available cant handle much power. So who here has actually had one fail & what stroke was it? If there has been a lot of failures i'm wondering if its related to a certain stroke. Also did it have steel or alum rods?

[grnmnstr]

We just tore my motor down. Forged China crank that was cryo'd. Making about 1000 hp. 4.50" stroke. Started losing oil pressure after about 130 passes. #2 and #3 mains were blackened on only half of the journal. ??? We assumed the crank was flexing. Rod bearings were fine.

We just ordered a Bryant billet.

[badgto]

I had my 4.500 in my 496 break in half on the top end. It was a eagle. Keith

[GTO Dan]

Originally Posted by slowbird

I keep seeing post stating that the forged cranks that are currently available cant handle much power. So who here has actually had one fail & what stroke was it? If there has been a lot of failures i'm wondering if its related to a certain stroke. Also did it have steel or alum rods?

Good thread. I was just about to start one after I read Tom V's comments on the other one. Thanks

[XSIVPWR]

Yes very good thread! even a little scary as I am in the process of building a 535 right now using a IA2, Scat forged crank, Oliver billet rods & ross pistons. Will probably only be around 800/825 hp.

[S/st 54]

Great thread! I've read previous threads ,in the past,about this very topic and and I have a hp number in mind that I don't want to go over. If it cost me 2 mph in the 1/4 then so be it I would rather keep racing another day than sit on the sidelines and wait and wait for parts.And I have heard of more than a few forged cranks breaking not sure of the brands but I have an idea of how much power they were making.
I think it's great the pontiac world has come out with parts Capable of making enough power that we can finally have this discussion.I just think it would be cool if the aftermarket crank companies could keep up with the demand.

[BruceWilkie]

interesting topic... I have to wonder also about stroke and rpm...especially knowing of a few cast 3.75 stroke cranks taking a heck of a beating and high power too. Two exceptions come to mind Brad Spidel ran an Armasteel at 1200 hp level for awhile...block fail took it out. Vin63 has run a 400 N crank in excess of 1800 hp and near 8600 rpm supercharged and 15% NITRO. How??? I think light parts, excellent prep and excellent balance and harmonic control... Certainly stroke plays abig factor... Vin63 wasnt too lucky with a 455 crank... exceptional for sure but... it does leave one to wonder. Espeacially considering we have also heard of billet cranks breaking on occaision. We need to learn more...

[mysticmissle]

do you guys think a crank will break at 962 hp but will live at 959.9999?
Its racing, there are components that are more prone to failure at level X. even if you spend 3200 for a crower billet or 5500 for a moldex with all the tricks, there is another part that will fail IF THE TUNE UP IS INCORRECT. those cranks may be junk if your $90 oil pump fails. then you need the $800 titan.
Kinsler, Kaufmans, Picketts, slow bird, and many, many others push the 950hp imagined threshold, but their set ups are correct. even I made over 900 at the crank on nitrous, on pump gas on the calculator Index or bracket racing can tune to a lower hp level for maintenance and reliability. Thats a budgetary and longevity choice. Nothing wrong with that.
my only point is this, I think more people push their 'junk' stock blocks, forged crankshafts, cast rods harder than alot of people think are the normal limits. Its their choice. Those are the people that impress by running faster than you, we, or I think they should be able to go with the 'junk' stuff.
Im going to go as fast as my wallet lets me. then if i break it. Im going to rebuild my junk. fwiw

[Jeff Kinsler]

I'm going to use my scat forged with nitrous. Shooting for 1350 + HP. think it will be fine.

[T Syron]

Originally Posted by Jeff Kinsler

I'm going to use my scat forged with nitrous. Shooting for 1350 + HP. think it will be fine.

Jeff,
Did you do anything special to the crank? Or is it an out of the box Scat?

Tom Syron

[XSIVPWR]

I do know my 4.25 stroke eagle cast/steel crank in the old motor coming out has been in since 06 freshen one 1 time in 09. Aluminum rods with over 500 runs

[BruceWilkie]

Originally Posted by mysticmissle

do you guys think a crank will break at 962 hp but will live at 959.9999?
Its racing, there are components that are more prone to failure at level X. even if you spend 3200 for a crower billet or 5500 for a moldex with all the tricks, there is another part that will fail IF THE TUNE UP IS INCORRECT. those cranks may be junk if your $90 oil pump fails. then you need the $800 titan. Kinsler, Kaufmans, Picketts, and many others push the 950hp imagined threshold, but their set ups are correct. Index or bracket racing can tune to a lower hp level for maintenance and reliability. Thats a budgetary and longevity choice. Nothing wrong with that.
my only point is this, I think more people push their 'junk' stock blocks, forged crankshafts, cast rods harder than alot of people think are the normal limits. Its their choice. Those are the people that impress by running faster than you, we, or I think they should be able to go with the 'junk' stuff.
Im going to go as fast as my wallet lets me. then if i break it. Im going to rebuild my junk. fwiw

You've hit on something big...tune... if you push detonation limits you can create all kinds of issues ...your oiling can cover/prevent bearing damage of very light detonation but it may not be enough to suppress the harmonic disturbances that detonation could create. I think that may be a bigger cause than we may want to believe. I believe it was on Scats site awhile back that timing gears with more than 3 keyways might lead to crank failure... there were other things listed.

[mysticmissle]

why would the timing gear effect it so much? the hollow areas between the keyways transfering/creating a harmonic issue that a solid sprocket does not? thats interesting thought. so now you need a timing belt or a gear drive to make over 850 hp safely. see how it starts?

[R 70 Judge]

Originally Posted by Jeff Kinsler

I'm going to use my scat forged with nitrous. Shooting for 1350 + HP. think it will be fine.

Have there been many Scat forging failures or have they been the other knock offs? It was my understanding that the Scat forging was actually quite good

I have a 4.25" Scat forging for my build. It checked out perfect out of the box.

[cfmcnc]

The tune is most importent for crankshaft life ,Detonation kills engine parts ,When we see the center mains showing distress the cylinder pressure curve is trying to' push the crank out the bottom' another reason to dyno every engine .Bill C.

[estep455]

i have had an ohio and a scat fail trying an eagle now and it will be the last time i use one. all at 4.50 stroke steel rods turning 7000 at shift thru the traps at 6600 (1/8th mile) steel rods. both broke with about 500 passes on them over the course of 2 seasons use each.

[XSIVPWR]

i did dyno my 474 and it liked 34deg timing. lost at 33 & 35. Probably won't be able to dyno my 535 but I know I won't run over 34.

[mgarblik]

We ran stock 72 and 73 455 blocks with N crankshafts at 1000-1050 HP for years without a single crankshaft failure. However, we ran a 2.200 rod journal allowing for a much wider fillet radius. Also BME aluminum rods, a light aluminum ATI damper, 5 Program Enginnering main caps. We also keep the RPM's at a conservative 7800 RPM's. Finally, after several years of running that basic combination, the block would fail, cracking at the #2 oil feed hole on two blocks. I still feel detonation was the ultimate root cause of those failures. Even though I have no direct experience, you would have to believe that ANY forged crankshaft, even the Chinese ones would be better than a super brittle N crank ? I would hate to think a stock station wagon nodular crank is superior to a forging!

[cfmcnc]

Originally Posted by XSIVPWR

i did dyno my 474 and it liked 34deg timing. lost at 33 & 35. Probably won't be able to dyno my 535 but I know I won't run over 34.

34 may be to much.Bill C.

[XSIVPWR]

Very possible Bill, That is why I say I will not go over 34. Will start out @ 30 or 32