formula_k

I've been looking at some 383 stroker crates on Ebay and the one I want has an Eagle 383 Cast Steel crank. I was wondering if that would hold up ok or if it should really have a forged steel crank. I just don't want to drop a lot of money on an engine and then the crank snaps or twists. Any advice would be appreciated thanks!

sofakingdom

iTrader: (1)

to what?

What is "alot of money"?

TheNuge876

building a decent 383 can end up taking a lot of money. Before you start getting into anything, you should plan out what kind of power you want from the engine and how your going to go about getting it, supercharger, etc. Once you decide that you can figure out whether you want a cast or forged one. But you need to plan out what you want to do prior to the beginning of the build.

formula_k

Hmm shoulda been more specific I suppose, sorry about that. I don't plan on using nitrous but a supercharger will probably come down the road. It's supposed to put out around 425-450 HP but it comes with the cast crank. I just don't see the cast crank being that reliable even though it's an Eagle. I mean the engine is built to put out that much HP without any mods, and I want to put the Holley Systemax II top end kit on it with the heads and all.

Coach Hawk

If your serious about running the juice or the blower, I would not run a cast crank. For high HP, high winding 383's, my personal favorite is the Callies Dragonslayer. It's not cheap, but you will never have to worry about your crank again. Just my opinion...

http://www.callies.com/catalog/cranks/dragon.html

Damon

450HP in a street driven car that only sees an occasional WOT blast and occasional high RPMs can live for YEARS AND YEARS with a cast crank. Most of my motors fit that description and they almost always use a stock cast crank.

450HP in a road race car or boat application that spends extended time at high RPM and/or WOT is a different story entirely. That's when you need a good crank.

grumpyvette

Damon

is esentially correct, a CAST STEEL crank is significantly stronger than a production cast IRON crank tho not as strong as a FORGED STEEL.
at the 450hp level its RARE for a crank to fail, unless the PISTONS OR RODS FAIL FIRST!
rods and rod bolts, and valve train problems are far more likely to cause problems.
Id use a CAST STEEL crank and spend the money saved on good (H) style connecting rods with 7/16" ARP rod bolts

this may help


"5140 or 4340 ? Get the Facts and End the Confusion."

Before we can answer the question "which metal do I need in my crankshaft". I think we need to take a moment and review just what each metal is made of and what are the best applications for each. In the following discussion we will see the strengths and weaknesses of each and with this information we will be able to decide which Crankshaft material will best fit our needs.

Starting with the basics, metals containing primarily iron are classified as "ferrous metals". They range from pure iron through exotic high-alloy steels. Stock Crankshafts are made from cast iron, a metallic iron with more than 2 percent dissolved carbon. One preferred variation, ductile or nodular iron has all its carbon contained in the form of tiny spherical graphite nodules uniformly dispersed throughout the metal's matrix. This makes the material more ductile (deformable rather than brittle) and eases casting and machining.

Even the best cast iron has only limited tensile strength. Increasing ductility, hardness, malleability and fatigue resistance requires removing most carbon and at the high end, alloying iron with other elements, creating "steel" an iron with less than 2 percent carbon

The most basic form of this is carbon steel, which contains up to 1.7 percent carbon and minimal additional alloying elements. Carbon steels are designated by a four digit number. The first two digits indicate the basic type, and the last two digits indicate the approximate midpoint of the carbon content. The "10" ID's these alloys as non-resulfurized carbon steel with some manganese (popularly called medium-carbon or mild steel). The second two digits the "45" or "53" means the steel contains about 0.45 or 0.53 percent carbon respectively. Stock forged OEM cranks are usually made from 1045 or 1053 steel. There are exceptions to this, some 350 high performance steel cranks in the sixties were made from 5140 and some manufactures offer 5140 or 4340 in their high performance aftermarket catalogs.

From these mild OEM steels the next step up is Alloy steel. Alloy steels allow for more variations depending on the alloying materials. Over time as manufacturing techniques improved and chemical knowledge grew., metallurgist developed whole families of alloy steels, custom-tailored to make metals stronger, lighter, more durable, more ductile, and harder. Alloy steels are also identified by a four-digit number, with the first two digits indicating the major alloying element or elements, with the last two digits indicating the approximate midpoint of the carbon range.

We will now examine the four most common groups of steel, we will examine their best uses and hopefully come up with a buying criteria for making a decision on our crankshaft purchase. We want our purchase to be based on knowledge of the product and its intended use.



4130 The best known chrome-moly steel. It is a high-strength/high-stress alloy when produced in thin sections (sheet metal and tubing). But 4130 possesses very poor deep heat-treating characteristics which make it a bad choice for machined or forged parts.
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4140 A deep-hardening chrome-moly steel , it forges well and has good impact resistance, fatigue strength and general all around toughness.
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4340 A nickel-chrome-moly steel, this alloy is used to make premium cranks.4340 has good tensile strength, toughness, and fatigue resistance. Modified 4340 alloys with vanadium and more silicon can make this already good alloy even tougher and more fatigue-resistant. The main drawback is cost.
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5140 This chromium alloy increases tensile strength, hardness, toughness, and wear-resistance over carbon steel. It has the same basic elements of 4340 and is made with the same process but is more affordable.
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So what can we conclude from this short primer. Our first conclusion is that we don't want to purchase a crank made from 4130. The lack of deep heat treating properties makes it unacceptable for most performance applications. That leaves us with 5140 and 4340. Of the two we feel 5140 is the crankshaft material that suits most clients needs. Reason #1, based on feedback from clients using our cranks the 5140 crankshaft lasts as long as the 4340 when used in all but the most extreme racing conditions. For applications where the engine is putting out 800hp or less and turning 8,000rpm or less, 5140 is the right choice. Reason #2, in engine building you save money where ever you can, if it doesn't effect the performance or durability of the engine and our 5140 crankshafts are priced 30-40% below 4340 crankshafts in cost.

short answer,forged is best, cast steel is significantly stronger than plain cast iron and can be slightly more flexable, unfortunately, as the quality gets better the cost gets higher, and your connecting rods are FAR more likely to fail than the crank in most engine combos below about 6500rpm

http://machinistinfo.com/types_of_cast_iron.htm

http://www.key-to-steel.com/Articles/Art1.htm

http://www.seaportsteel.com/TechHeat.htm

http://crankshaftspecialist.net/cryogenics.html

http://carcraft.com/techarticles/116...to/index1.html

Tibo

iTrader: (15)

There is a lot of misinformation floating around about crankshafts. There are mainly 3 different categories of cranks: Cast iron, cast steel and a forging.

cast iron is what the fastory (chevy) uses in our cars. It is not the strongest, but stronger than what many people are told. Author David Vizard has tested many SBC's. One of them was a motor assembled with a stock rotating assembly. All cast. He then ran nitrous on it until something "gave up." He reached over 1,000 hp when the cylinder wall of the block cracked. Many peple are also able to run larger shots of nitrous on there stock blocks and run them for years. Usually when you hear of a crank "breaking" it is due to excessive heat in the chamber or because of detonation, which can also be from heat. If these factors are monitored closely, a cast iron crank can hold up to quit a lot.

A cast steel crank is stronger than a cast iron crank. It has been heated up thousands of degrees and then purged in a liquid solution. Now there are oxygen molecules in the small once empty spaces of the iron and the structure is stronger because there are more bonds to hold the metal together. Power levels on these is above 450 Hp. I think that the LT1's make almost 375 Hp at the flywheel, and they are cast iron. They just rate them at that so someone who cannot properly ssemble an engine and not tune it will not go and try something foolish.

Forgings are of course the strongest, the heaviest too I believe. they are needed for the real engines that are going to produce high power levels for extended periods of time on a regular basis.


Do not fal into the trap of "I am eventually ina few years going to put a supercharger or N2O on a motor." That is foolish. You need to build a N/A motor or a supercharger engine. If you do not know that there are large differences that ned to be accounted for, you have no business even thinking of building one yet. Compression is just the tip of the hat.

Ricktpi

One point not mentioned, lesser quality cranks can flex with high horsepower loads. While they may never break, they transmit harmonics to all attached & surrounding parts, bearings, rods, pistons, balancer, flywheels, etc. causing their failure.

Tibo

iTrader: (15)

True, but the forged steel cranks (even cast steel to a degree) are much more brittle, instead of flexing, they just crack. Assumnig you are at the conditions in an engine to exert the force needed.

formula_k

It sounds like the cast steel will work for what I'm looking at. I think the forged steel will be a little overkill. Thanks for all the input y'all and if anybody else wants to add somethin please do!

shaggy56

Interesting quote on this subject from A. Graham Bell in his book, 'Forced Induction Performance Tuning'

D's89IROCZ

now I am lost.

Tibo

iTrader: (15)

Cranks can be forged from many different metals. Remember that that author is talking about factory forged cranks. Seems like the author is trying to take a jab at American cars. For that reason I think that it is redundant to put that in his book.

I would not listen to this guy about crankshafts, engine tuning maybe. It sounds as if he is contradicting himself. First he says that the american FORGED cranks are not good for racing or competition. Then he says that the CAST american cranks can do right under 500 hp for a long time? By that reasoning a forged crank should be good for a couple hundred hp past 500, and that is not performance quality?

For engine building and crankshaft selection I will stick with the people who are actual mechanical or aerospace engineers, such as David Vizard.

shaggy56

I dont think he is contradicting himself at all. He is actually stating that the cast cranks made from the American factories are better quality than the forgings they use. So how is that a jab since he is complimenting the cast version?(This is a good thing right?).

It is a fact that the quality of factory forgings are generally a lower quality than an aftermarket forged crank and probably as durable or less than an aftermarket cast crank. I dont think you have any idea about different grades of steel since he is discussing the lower grade factory forged cranks. Factory crankshafts in general even the 1053 forgings that GM makes are not intended for high performance use. The article above is making a point if you had to choose between a factory forged or cast crank to choose the cast version for other reasons other than the material.

Tibo

iTrader: (15)

I was only disagreeing with the author last time, now I am going to disagree with you on this. Comparing one chevy crank to another is fine, it will help out chevy guys choose a crank. Comapring a Chevy crank to a Honda (or whatever) crank only works as an attempt for the author to show of what he might know. It is comparing apples to oranges, not apples to apples. I will never use a Honda (or whatever) crank in my chevy car. Do you see why that is futile?


I would rather go with a forging, not a casting. I could be wrong on this too but I think that almost all of chevy's cast cranks made in Camaros and Firebirds and GTO's, etc, were iron, not steel. I am finding it very hard to believe this author that the forged cranks are not stronger and that the cast cranks are good only to 500 hp. I have read many books, articles and tests of cast chevy iron cranks sustaining higher power levels and being OK. Many people on here even run around with hp at the crank in excess of 500 hp and are fine. You can easily get 400hp at the flywheel (usually 300 at the wheels) on a mild rebuild with a carb and good intake. There are also those people that have N20 shots that can put down high numbers. Sure those people can and have broken parts, but it is usually something else that goes.

Heck, I think I even posted above how Vizard was able to take a stock bottom end to 1,000 hp and did not break the crank.

shaggy56

High Perfromance muscle era cars as well as high performance factory engines came with forged crankshafts. Aftermarket forged crankshafts are much stronger because they have added chrome like the 5140 forged crank. This is the problem with the typical factory 1053 forging because its a basic soft steel forging. I did some research and found some interesting info about the GM forging which may lend to the reasoning behind this. Forged cranks are softer than cast cranks but cast cranks are harder and brittle but are better at long term wear. So you can see how the 1053 forged crank will be the softest since it lacks the chrome like a 5140 crank but doesnt have the long term wear like a cast crank. The 1053 is not much stronger than you average cast crank.

most forged cranks are nitrided, which is a bearing journal treatment that increases the hardness of the surface so impurities in the oil that get stuck between the bearing and the journal do the least damage to the crank journal. if a GM crank has to be cut. They should be re-nitrided because GM's nitriding doesn't penetrate as deep as some aftermarket crank manufacturers. re-nitriding is expensive. if your looking at cutting a GM crank and re -treating it it may be worth it to just buy a new one.

In any case most of the forgings GM put in engines are old and fatigued from time. This is getting off topic since the main reasoning was placed for the fact that the cast crankshafts can hold their own.