Inliners International Forums General Discussion Hi Performance Forged Crankshaft for Chevy 250

Hey Guys!!!

On the last race with my Orange car, I used the last Stock Crank I had here, with Standard measurements on main and rod.
So, I'm starting to build up the engine for my 1300 hp project, and I don't have here more Stock crankshafts for that car, and I was wondering to use a Forged Custom unit...

We have here in our town one of the best crankshaft builder of Latin America. It calls SUSIN FRANCESCUTTI crankshafts. They build cranks for PAUTER MACHINE and for EUROSPEC. They are the official crank supplier of truck racing here in Brazil. Those cranks are really a peace of art...

But talking with some guys about a forged crank for teh Chevy 250, they told me that the forged cranks can broke easier than the stock cast iron unit, because the forged one can't handle the vibration so well like the stock cast iron one!!

So... what do YOU GUYS have to say about these???


Thanks!!

Douglas Carbonera - Brazil

A forged crank for a 300 Ford is about 40% stronger than its cast iron counterpart. This I was told by a Ford crankshaft engineer. I would just use a good vibration damper on the forged crank.

If you go with a forged new crank.
I would make sure it has huge radius's (SP) where the rods & mains are machined.

Then you will have to cut or narrow your rod & main bearings to have clearance form the bearings fron hitting/touching the radius's.
Hope that makes sense.

MBHD

HI Bruxu

How much r$ for new one? would he give a discount for 2 cranks? :p


Edy

$2500 US From what Douglas told me.

MBHD

i was reading an article in carcraft.com about cast cranks vs forjed cranks... i got scarried by difference in strenght between them.

http://www.popularhotrodding.com/tech/0710phr_crankshaft_tech/index.html

Edy

Hank

4340 steel?

4340 steel?


Not sure of material,ask Douglas or the company that makes them.

MBHD

In general forged crankshafts are stronger then cast crankshafts. As always, and in particular for the Chevrolet 250 the past application of the design and materials is important. Per Leo Santucci' "Chevrolet Inline Six-Cylinder Power Manual" the forged steel crankshafts, '63 - 64', had narrower crank arms than the later cast units and six counterweights. The nodalur cast iron '64-'66 crankshafts had six counterweights. The nodular cast iron '67 and later crankshafts had 12 counterweights. So for the Chevrolet 250, in the previously built forged versus cast crankshaft comparison, other significant factors are important.

AISI 4340 is a strong, tough, steel. On of the standard super steels. In general, when you need something stronger and tougher than the standard chromly's, though technically it is a type of chromoly. Good for axles, shafts, landing gear, connecting rods, etc. It is tougher to machine than the lower strength alloys steels.

4340 (chromoly) Normalized Alloy Steel
Minimum Properties Ultimate Tensile Strength, psi 186,000
Yield Strength, psi 125,000
Elongation 12.2%
Rockwell Hardness B100
Chemistry Iron (Fe) 96%
Carbon (C) 0.37 - 0.43%
Chromium (Cr) 0.7 - 0.9%
Manganese (Mn) 0.7% max
Molybdenum (Mo) 0.2 - 0.3% max
Nickel (Ni) 1.83%
Phosphorus (P) 0.035% max
Sulphur (S) 0.04% max
Silicon (Si) 0.23%


In comparison to AISI 4130

4130 (Chromoly) Normalized Alloy Steel
Minimum Properties Ultimate Tensile Strength, psi 97,200
Yield Strength, psi 63,100
Elongation 25.5%
Rockwell Hardness B92

4130 (Chromoly) Annealed Alloy Steel
Minimum Properties Tensile Strength, psi 81,200
Yield Strength, psi 52,200
Elongation 28.2%
Rockwell Hardness B82
Chemistry Iron (Fe) 97.3 - 98.22%
Carbon (C) 0.28 - 0.33%
Chromium (Cr) 0.8 - 1.1%
Manganese (Mn) 0.4 - 0.6%
Molybdenum (Mo) 0.15 - 0.25%
Phosphorus (P) 0.035% max
Sulphur (S) 0.04% max
Silicon (Si) 0.15 - 0.35%

Nascar engines use forged 4340 steel cranks,some carved from forged billet or forged into shape.Nevermind the V engine,750 plus hp at rpm's between 6500 and 9000 for hours on end is a torture test.

As far as I know, there are no (stock) forged 250 cranks.
Only forged cranks available (stock) are for the 194 CI & the 292 CI engines, & both of those forged cranks are weaker than the cast units.
I have heard of forged 230 cranks,but those are the same as the 194 cranks.

MBHD

There are titanium crank shafts for SBC. Certainly aren't going to be the economical solution. There was one in our JF Fuel dragster it was on the dyno at 950hp.


Larry

The crank in my Mercruiser 250 looked like some sort of steel crank.It had a lot of machine work on it and balance holes drilled and some that were welded up part ways. All kind of purple lay out fluid and numbers painted on it. I know for sure this motor had never been out of the boat I took it out of. Compared to the crank in another 250 motor out of a 69 chevy pickup it was totaled different. When i had my motor balanced the crank was perfect. On the subject of cranks I have a 292 crank that IS A CAST crank with 12 counter weights on it and 3 dowel pins on the flange. I wonder what this came out of ???

What Douglas and i mean, is that we invested a lot of money in internal engine components and we are really concerned in putting in risk all that high priced parts. As Hank said is known that stock forjed cranks are weaker than the cast ones, but now is clear (at least for me) that a billet 4340 crank will be much more stronger than other kind of crank. we are talking about Chevy´s 250 making 1000HP+ and it´s a unknow world here in Brazil...

I just got his from Robert A. Jones from Scat Cranks

"That is one heck of a motor. The inline six motors are a smoother motor with the 120 degree power pulses but your going way beyond what a cast Iron crank was ever designed for. Since it is turbo that helps a lot but still If I had the budget I would billet it. Saying that I don't make a billet for your motor but if you call Moldex 313-561-7676 they can"

Edy

Read a couple forums on Moldex cranks.
Long waiting periods 8,10,12, months & more.
Saw another forum where a Moldex crank for a inline six crank cost $7000 US.
But ,give them a call if you really want one, what is the worst they can say,OK, that will be $8000? LOL, Not funny I know.
MBHD

My GMC crank from Moldex cost $3800 and took six weeks. Henry Velasco in So Cal will make one for about $3500 with a four month weight. I had a quote from Crower for $4000 if they had to do the drawing. Weinberg wanted $7000. These numbers are all within this year. Anything more than $4000 is too much. Years ago Hank the crank made a GMC crank for Bruce Johnson's stream liner for less than $2000, now that company is part of LA Crank. Their are also many others in NASCAR country with CNC machines big enough to do billet ones for this price range.

Any body know what the weight of a stock 250 vs these light weight cranks?

Steven