[i82much]

Yeah considering what most guys have in their engine, a Chinese forging isn't that much more. And, as great as the factory cranks may be, I have not heard anyone suggest they are better than the Chinese forgings.

Of course, whether you want to run around with Chinese parts on your car is another question.

[BruceWilkie]

Originally Posted by GTOGEORGE

For me this is kind of SILLY.........if you have the MONEY to make the HP to WORRY about BREAKING a CAST crank then you have the MONEY to step up to a FORGE crank...........why RISK it. Then again what about the BLOCK? Here we go again! Just like SAFTEY EQUIPMENT the more HP a RACER makes the QUICKER HE RUNS and the more SAFTEY EQUIPMENT he NEEDS which equals MORE MONEY!


GTO George

Any crank can be broke... past few years there have been reports of a few china forgings that broke as well as billets... In all cases best I can tell... crank strength in terms of Horsepower amount itself had little to do with failure! In other words it wasnt the amount of torque applied that caused the failure.

RPM, Stroke, Recip weight, connecting rod material all have a big role in loads imposed on the crank. Applied torque contributes. However, excellent harmonic control and avoiding stupid things like belts too tight, balancers poorly fit, pushing detonation limits, etc. will go a long way with just how much abuse a combo can take.
Keep in mind, cast ,forged, billet, each has a different point of critical harmonic frequency. The more flexible the crank the more forgiving it is,,,to a point(too flexible not good either)... any of the 3 types can fail.

BTW George, (curious not rying to be a smart ass )have you addressed the cause of your billet crank snout to break last year? Hub problem, belt too tight, machining issue ???

I'm not telling anyone a factory cast crank is a better choice over a good forging or billet... simply pointing out that factory N castings are pretty tough and with good practices and plenty of attention to harmonic control they have shown good life at high rpm and high hp levels.

[GTOGEORGE]

Originally Posted by BruceWilkie

Any crank can be broke... past few years there have been reports of a few china forgings that broke as well as billets... In all cases best I can tell... crank strength in terms of Horsepower amount itself had little to do with failure! In other words it wasnt the amount of torque applied that caused the failure.

RPM, Stroke, Recip weight, connecting rod material all have a big role in loads imposed on the crank. Applied torque contributes. However, excellent harmonic control and avoiding stupid things like belts too tight, balancers poorly fit, pushing detonation limits, etc. will go a long way with just how much abuse a combo can take.
Keep in mind, cast ,forged, billet, each has a different point of critical harmonic frequency. The more flexible the crank the more forgiving it is,,,to a point(too flexible not good either)... any of the 3 types can fail.

BTW George, (curious not rying to be a smart ass )have you addressed the cause of your billet crank snout to break last year? Hub problem, belt too tight, machining issue ???

I'm not telling anyone a factory cast crank is a better choice over a good forging or billet... simply pointing out that factory N castings are pretty tough and with good practices and plenty of attention to harmonic control they have shown good life at high rpm and high hp levels.

Bruce,
Seriously the CRANK was 10-11 years old and ALL that time being yanked on by the BLOWER........you tell me why it gave out.
If I'm going too build an engine to race Im going to buy the PARTS that give the engine the BEST chance of surviving.........not parts that are just OK.....MAYBE! YES, anything can BREAK BUT......................!


GTO George

[vin63]

Originally Posted by BruceWilkie

Any crank can be broke...

Yep, and it doesn't matter how much money or what someone thinks are the best parts, if machining and balancing is not good, or you miss the tune, catastrophe ensues no matter the material of the crankshaft. We had a really good handle on the alcohol tune and the machining/balancing, so, we were pretty confident about running the Nodular 400 crank. After switching to nitro we went with Ohio forged cranks. We have since cracked two forged cranks, in each case it was when we lugged the motor (put out one or more cylinders) and had a bearing failure. We seemed to have solved that problem, but it's just indicative of how quick damage can be done. It happens often to the NFC guys even with their billet cranks...my racing partner builds the engines for GT's Pedaler nostalgia funny car and does the bottom end at the races. The difference is that sometimes they can repair the billet cranks.

[mgarblik]

X2 with VIN63 post. We were worried years ago about using the nodular crank in the Grocery Getter. Had an opportunity to buy an SD 990 crank and bought it, prepped it properly and put it in the car. In less than 20 runs, we had a clutch switch fail intermittently in the nitrous system and guess what? We cracked the high dollar, holy grail of factory cranks!. It was right back to the N crank cause that was the choice in those days. No Chinese stuff. Either factory cast, billet or ancient forging. Yes, tune-up and potential detonation have a huge effect on crank life. So, I will go out on a limb here. If my tune-up was right, correct balance and a press fit ATI balancer, I would not give a second thought to running a stock crankshaft to 850 HP. I genuinely feel it would be fine. I would be much more concerned about a Chinese cast crank due to little or no oversight as to the metal composition, casting and finishing process. The only thing they care about is cheap. period. Personally, I would rate a Chinese forging only slightly above a Chinese cast crank for the same reasons, although inherently, it should be much better. Tom Vaught is always talking about Timkin bearing quality steel billets for crankshafts and he makes a good point. This means the steel meets or exceeds the quality standards to make bearings. When you buy a Chinese cast or forged crank and they say it is 4340 steel. That is an entire category of steel and I can almost guarantee you Chinese 4340 barely meets the minimum standard, if at all. Pete Harris , who makes our billet cranks at Crower said they did some extensive testing of steel billet stock from China, as they were considering doing a lower cost billet crank years ago. Their tests on the metal itself were all over the map as far as material composition and quality. Look it's no secret Chinese stuff is cheaper. Most of it is labor, but not all of it. Material quality is also a factor.

[adam woodmancy]

im actually a little nervous about the forged cranks. I have three friends, all regulars on here and in the last 3 years, these 3 guys have broken a total of 7 forged cranks.. all brands, eagle, ohio, scat... ect... different strokes too, 4.25, 4.50 and 4.75. No a guy could say, maybe so and so doesnt know what he is doing... fair point... but to have it happen to three separate, very good and experienced racers in a matter of 3 years has scared me away from the forged cranks..

If i could find a factory 455 N crank that was turned down to fit my 3" main blocks, i would feel better going that route under 900 hp

[vin63]

Just as an example...4 years on the Nodular 400 crank (still have it under the bench) with 100+ passes in NE1 and 7.0 Pro, no issues.

Forged 400 crank 6.35 ET no issues all journals cherry. At Phoenix - 7.20 ET had to pedal it twice (should've shut it down the first time) cracked crank.

[Elarson]

We've really abused the Crower billet that's in the Boss Bird. Dropped cylinders, pedaled once, burned bearings (and bent crank) and then straightened crank 3 times. And it's still fine.

Eric

[BADDTA]

Originally Posted by Elarson

We've really abused the Crower billet that's in the Boss Bird. Dropped cylinders, pedaled once, burned bearings (and bent crank) and then straightened crank 3 times. And it's still fine.

Eric

I chuckled when I read that Eric! Lol. That's awesome!! The funny car is just SICK!!
I love it!!!!!!

Brian

[i82much]

Help me out here - what do you guys mean by "pedal"?

[GTOGEORGE]

When you lose traction and the car gets out of the GROVE (rubber tracks on the concrete or asphalt).......... Getting on and off the gas pedal ( pedaling).


GTO George

[i82much]

Originally Posted by GTOGEORGE

When you lose traction and the car gets out of the GROVE (rubber tracks on the concrete or asphalt).......... Getting on and off the gas pedal ( pedaling).


GTO George

Thanks George. Does this contribute to breaking cranks somehow?

[vin63]

Originally Posted by i82much

Help me out here - what do you guys mean by "pedal"?

It means that we have overpowered the track at some point during the run and had to get in and out of the throttle quickly. When we lose traction and the engine free wheels with no load, one or more cylinders go out, but the fuel keeps pouring in. This severe imbalance of some cylinders firing and others not firing can be catastrophic to bottom end parts. Here's a video of our car overpowering the starting line a couple months ago. The track photographer caught the car just as it hiked the front end and then went into wheel spin and put out the #4 cylinder. That instant of wheel spin sent our RPMs to 10K, which means the fuel pump was sending way too much fuel to burn.

http://youtu.be/rV2vODpnzjI

[GTOGEORGE]

Originally Posted by i82much

Thanks George. Does this contribute to breaking cranks somehow?

YEP!

Now that you brought it to my attention I did have to pedal my car 3 times on the pass before I broke my crank last year at Norwalk!


GTO George

[Willshire]

What about heat treating or cryo? Additional Rockwell can't hurt can it?

[Don Chapman]

Here is the thread of the car i was talking about. Jimmy Jammel was the owner.
http://forums.maxperformanceinc.com/...highlight=8.08

[Dragncar]

Seen a lot of engines blow during a burnout and just after crossing the stripe as they get off the gas.
Seems those rods like to be compressed under acceleration more than the like to be pulled apart getting off the throttle.

[i82much]

Wow, I had no idea losing traction was so hard on an engine. I assume this is a bigger deal for boosted engines or maybe running a lot of nitrous? Is a naturally aspirated car ever going to hurt anything by backing off the throttle?

I guess I don't quite understand why running the engine up with very little load and then backing off the throttle causes so much fuel to be dumped in, I would think the carb would still meter it. But I don't know much about high-end engines, just street stuff.

[Half-Inch Stud]

On the other hand; 300+ foot wheelstands (Langer) during Eliminations might be good for the crank.

[Cliff R]

The offshore cast cranks are a ticking time bomb, and not suitable for big power. Everyone I've known that has used them had issues. One of my customers broke two of them at 735hp. One last 2 seasons, the other lasted about as long as it took me to type this.

Early cast steel cranks (and even some of the later ones) were WAY off on the machining and very poor finish. Don't ever get the mic out during engine assembly or you will be sending it back! Just put it together, say a few kind words or prayer over it, and go racing.

We've had perfect success with the forgings to 750hp, and all of them that we have installed are still getting it done with zero issues anyplace. We've freshened up a couple high HP set-ups, and just rolled new rod bearings in them and put them right back in service.

One of my customers recently pulled 455 out to freshen it up, and his Eagle cast crank had over dozen cracks in it, but had not failed yet.

I will not use them here at any power level.....FWIW......Cliff