As far as cranks are concerned, the three top crank brands are Cola, Crower, and Callies, from what I read. You shouldn't go wrong with any of those if the machine work and balancing is up to par.

 

Thats definetly user error. If I read this right, the crank snapped externally from the motor. Thats out of the engine builder's hands, like mentioned before, belt too tight is a HUGE load on the crank.

 

thats what it seems like now i guess
no one has ever mentioned this to me before so i never knew a crank snout could just snap like that.

 

You know never heard of this **** before but i guess now i did, and its too late as far as 750rwhp goes i dont think my goal is that high but defanatly i was planning on just to tap a little over 700 mark. but like i mentioned before the car was never really pushed i was still braking the motor in and just hit a 400 mile mark, the car only has 50lbs injectors and fmu still. My plan was to brake it in, and put mototron 60lbs injectors and get rid of FMU...but looks like now time for another rebuild. Tomrow i'm going to call Eagle and see if they at least can work out a deal with me on BB snout crank.
thanks for the replys guys
this board rocks

 

The crank drive pulley stick's out a good bit,and you have a hell of a lot of leverage pulling sideway's on the crank when you tighten the belt TO tight.If the belt was slipping you need a 12 rib belt or a cog belt to prevent this again.Don't pull the belt dick band tight to try to stop it from slipping or it will happen again even with a BB snout.If it is slipping you NEED a different belt,period.

 

WOW
Thats terrible. I had never heard of that either.
Good luck. Let us know what Eagle says.
I'm using a Eagle 4340 lightweight crank but without a blower. I went with Eagle because a coupe machine shops in the Phoenix area said that the Callies Dragon slayer had broke.

 

Thanks for the advice i do have a 12 rib set up

 

i'll keep you posted i'm waiting for eagle to open right now

 

This is one of the reasons why a good freind of mine that races regularly (runs mid 8s in a 67 Nova) doesnt like superchargers, he thinks the extra bottom end work and special parts to make it run right and reliable (to a point) are not worth it, thats why he sprays it hard (500 1st stage 250 top end stage).

He has run Eagle 4340 forged cranks in the past and he says he had no problem with them making over 1000 hp!! of course this wasnt on a blower motor. He's using a cola crank right now.

 

well Eagle totally blew me off today, not willing to help.
i'm waiting on my machine shop guy to give me a call back with a price on a new crank, bearings and while i'm at it i'll go ahead and take that 847 cam out and already talked to Joe O, he'll grind me something nice

 

Was it just the front main bearings that were eaten or was the thrust bearing eaten as well?

 

I too would like to see the front main bearing, especially the top half. I have see them worn thru to the steel backing due to blower belt load! That kind of load on the crank nose causes quick fatigue cracking especially near any keyway machining or grooves in the crank nose, or at the rear end of the balancer. If that's where it broke, and the front main is worn, it's a very predictable failure.

While it's difficult to do, the blower belt should be right next to the timing chain cover, not hung on the front end of the balancer. Of course that's not how most are done as add-ons. Durability, like speed costs money. How fast (or how long) do you want it to run?

The BBC size snout will help, but getting the belt closer to the engine will help a LOT as will less belt tension.

My $.02.

 

How far back did the crank break. You stated that there were still threads on the end of the crank..That tapped hole must have been deep for it to break behind the pulley and STILL have threads right! sounds kinda weird to me but who knows.

 

That will definately help, but if you are doing a custom setup, I think the best thing to do is run a cogged belt. A fairly simple stress analysis will show you that a load on a spinning shaft can cause massive shear stresses. A cog drive runs almost no tension. Like you said, "speed costs money".

Out of curiosity, did the crank break straight acrossed (perpendicular to the way it spins) or did it break in a diagonal?

Dustin

 

Ok as far as BB snout goes its pretty much out of question.
I called Eagle they said they dont make Custom Cranks, they told me to try LUNati. So when i called lunati they told me the only SB crank with a BB snout they make is for 2 pieace rear main seals.
As far as how it broke, about 1/4 of an inch to 1/2 an inch is still attached to the hub/pulleys and about 1/2 to an inch of the actual snout is still on the crank. Its broke flush like i cant see where it would crack or anything but it looks like it shattered in two pieces completly flat down. I'm looking into getting a COLA crank this time and just keeping the tension easy on the belt i will probably consider a cog system later down the road, but i heard cog drivability sucks but i'm sure its better to be not driver friendly then not drive at all...right?