BBC Crankshaft Myth

Ive been told by everyone and their brother that you CANNOT run a cast steel crank with power output above 750 to 800hp without certain failure. I would like to verify that this is total BS. Ive been running a CHINESE brand (RPM) cast steel 4.25 crank for over a year now at 8000rpm at 1800hp. 565 with a 14/71 SSI at 20lbs of boost. Never had to had it turned nor has it failed. I will say that it seems to be flexing a bit because Im putting mains in it about every 10 passes or so. However the crank still looks good and so far (knock on wood) has not cracked or failed. By the way this crank cost a staggering $159 off Ebay. Beats the Hell out of spending $2800 for a "BULLETPROOF" job.

 

Cast Crank

I'm going to put my opinion in here if a may. I believe the reason people say "don't do the cast crank race engine thing" is because history has proved that they are alot weaker that forged/billet cranks. The first person any racer will come back to "if" their cast crank lets go will be the guy that said it would last to 1800HP. So no one recommends it. Take a piece of cast iron put it in a vise and try to bend it, it breaks. Do the same to a peice of steel, it bends. I think this says it all.

I'm very happy that your cast crank has worked so well, but I'm sticking to the forged/billet steel ones.

Just my opinion
Corey

 

Agreed. We won't even cryo-treat anything cast because it will only make it more brittle and can even crack it in the process. Castings have a MUCH greater porousity/less density because there is no pressure other than the weight of the metal itself when forming. Forgings use hammers and dies to more tightly pack the material. Raw billet materials are generally formed in the same fashion using heat and pressure. This is also the reason you generally don't see anything made from castings that is SFI approved for racing, other than blocks and blower housings.

 

Fair play to you and that your combo is working but I have to say I do think that your brave using cast. Its fair to say that any crank can break but using cast is just giving it a much greater risk of doing so. But its your deal and its working for you.

 

I'm no pro by any means, but I would still have a hard time trusting any cast crank at 1800 hp, a good forged or billet crank is good insurance in my opinion and well worth the extra $$.

 

What are you running for a block, rods & pistons? What did you get the HP number from?

 

Only the best parts....lol

I use a Merlin 2 cast main cap block (Bought Used for $1200). Used MGP rods bought off of Ebay ($102.50) Used JE pistons and rings ($125) So the only new item was the crank which i bought from 909 Raceparts off of Ebay as well for $159. I do believe the price is now $189. (inflation...lol) I have never dynoed my engine so as far as having firm number on paper I do not. However, My car weighs 2505 with me in it and runs 4.60's @160mph FOOTBRAKING. We did the math and that comes out to around 1800 give or take a few. Now I am not saying that cast steel cranks are stronger than billet pieces. All I am saying is that you cant always believe what you hear until youve tried it yourself. Here is the ol junker in action. http://www.pbase.com/fuelcarfan/09topmajuly10

Its the one with all the cuties on it......lol

 

I am impressed.... That is cool man!!!

On a side note, your car looks just like mine.... I am running a 498" BBC, 4340 Crank, Steel Rods, 10.7 to 1, 25 pounds of boost, Canfield Heads... My car weighs 2650 with me in it and the 4 speed lenco... Not sure what it is gonna go yet, our first time out, the track was crap and we went 5.33 blowing the tires off, peddaling, and letting off around 400 feet.... We ran 101 mph.

Check out the pics.

Your Car.




My Car.

 

Sweet ride

Nice car dude. Where you run at?

 

I run up in Maine / New Hampshire....

I was running a Blown 540 62 Nova last year... Picked up this chassis last fall from a guy in Florida ( he moved there from Texas where the car was built ). He put 35 passes on it with a Nitrous 632 running in the 4.40's. It is 25.1e certified, runs a stock corvette body / doors... Front end is glass ( appears to be basically the same as yours )

We built the 498" motor this winter and put in a 4 speed lenco with mcleod clutch. It took us a lot longer than we expected to get it done so we have only been out once this year. It was in the middle of 4 weeks of rain so the track was crap. We will be running again this weekend seeing if we can get some good runs / data.

 

Here is last years ride...

It went 4.80's / 7.60's at 3000 pounds with a glide....

 

wing

Love that Top Fuel Wing on that thing. Good Luck with the Vette.....Looks Great!!!!!!!!!!

 

Wheres the close up shots of the wrap on the blue corvette?
Mostly the sides

 

here ya go

http://www.pbase.com/fuelcarfan/09topmajuly10

 

Money shot, just saw you have a pull only throttle cable (not a morse style). That will pass tech? I thought you had to be able to pull the throttle closed (toe loop???) Just dawned on me, Outlaw Pro Mod...never mind.

You have a LOT of faith in throttle return springs.

http://www.pbase.com/fuelcarfan/image/114828646

 

Yeah, Not so sure I would pass NHRA or IHRA tech of any sort. Im just having fun trying things they say cant be done. By the way. A Coca Cola 24pk makes an awesome blower base gasket too......lol

 

My blower gasket is construction paper (injector to blower).

 

IM not trying to be funny, but I noticed you don't have a diaper on the motor, IFFF that crank goes, it might save your car....just a thought

 

Really, one of the best investments to save your life not to mention your car. Can tell you that from experience. Spend the $250 and have that comfort and piece of mind for you and your family. It also gives you the confidence to push it further.

 

Do what you want, but if I ever get paired with you, you will get a single. To me, that is simply a safety thing. When (not if) that thing explodes, it's gonna be ugly and I don't want to be anywhere near it. My BH puckers thinking about running low buck steel cranks but I know if it breaks, it won't come out in a hail of iron missiles. Just my .02