cause of broken crank keyway?
 

my 383 D1 in my 69 camaro had some balancer problems. the keyway broke and the balancer hub is cracked right down the keyway guide. whats the cause of this failure in your opinion? can't remember if i had a hardened steel woodruff key or just a stock one from my original 350 (if there is a difference?).

do you think the woodruff key broke and the balancer cracked from the stress as it spun off or did the weak spot in the hub crank giving play resulting in the keyway failure?

just curious. should i put a hardened woodruff key backin and a new balancer and hope its fine for next year or go through the PITA to pull the engine and have the crank and balancer double keyed?

thoughts.

thanks,

mike

Check out these for info.. Welcome to my world :D

http://web.camaross.com/forums/showt...threadid=94281

http://web.camaross.com/forums/showt...threadid=94282

http://web.camaross.com/forums/showt...hreadid=202609

Too much pressure on the crank pulley will cause the keyway to break, next thing is your crank is going to break..

--Sean

I had the same issue and it turned out to be that my crank bolt was backing out.. I ended up buying an ARP crank bolt and using some red loctite. :)

God, I wish that would've worked for me :D

--Sean

what about this option. instead of pulling the engine and tearing it down to have it double keyed, what about an innovative west custom balancer. after talking with their tech, he feels double keying is better than a single key, but the weakness is where the key guide is in the balancer and how thin it is. he said the best option is to go with a custom balancer that has the ID of my sbc snout and an od of a BBC. they make covers that match up to the SBC but have a seal opening for a BBC snout and balancer. also, a belt drive would be cool also but expensive, but help in tuning easily.

so thats the direction i am leaning right now. put a stron single key in but a very thick hub that WONT crack.

thoughts. think that is as stronger or stronger than a double key.

thoughts.

mike

That's exactly what I had made .. ATI (Superdamper company, not procharger) made that exact piece for me.. I got it, it's a quality piece, but hasn't gone on the car yet, as the engine is out for a rebuild..

http://users.csionline.net/~dawulf/i.../NewATIHub.JPG

http://users.csionline.net/~dawulf/i...NewATIHub2.JPG

http://users.csionline.net/~dawulf/i...NewATIHub3.JPG

http://users.csionline.net/~dawulf/i...NewATIHub4.JPG

In speaking with Scott @ SD Concepts, he doesn't think a double key is necessary, he runs a few +1500 HP cars with single keys.. Also, he said unless the keyways match up 100% perfectly, all the stress is going to be on 1 key anyway..

Of course, the ATI design has 2 keyways in it, but, I am only going to run one ..Of

Good luck!

--Sean

cool. so ATI built yours. how much? innovative west wants 350. i do have one question. this may seem silly, but i am not sure why your hub is seperate from the balancer. is that because its a late model set up? my damper is one piece with hub and balancer welded. is yours a bolt together or are you not running a balancer at all? just confused about what exactly defines the "hub" piece? any help appreciated.

thanks,

mike

The LT1 has a separate hub that mounts to the crank, then the balancer bolts to the hub .. The supercharger pulley has a spacer then mounts to the balancer..

http://users.csionline.net/~dawulf/i...Damper&Hub.JPG

http://users.csionline.net/~dawulf/i...s/ATItoATI.JPG

The hub cost $150 and the ATI Superdamper cost something like $300.. I forget exactrly, I have the receipt at home.. All in all, the package cost like $75-100 more than the ATI Superdamper for an LT1 you can get from summit ..

--Sean

cool. that helps. thanks

mike

alright, i got my new cloyes aluminum 2 piece timing for a sbc with a bbc snout opening. i am ordering the ati hub and balancer same as you Sean94Z. not sure if i will double key or not.. probably not. wish there was a place near me (cleveland ohio) that would do the additional keyway in the crank like second street speed did for baxter, but not worth a trip to the otherside of PA from here.

finally, i am looking for a good woodruff key now. i am not sure what the local shops around here have or if they are even hardened? assuming the hub wont crack with the additional meat, i'm thinking the key is the weakness now.

anyone know how to tell if a woodruff key is hardened or a supplier of strong keys? isn't titanium super strong.. why couldn't you make the key(s) out of a small stock of a this or a super hard metal or is that just necessary?

thanks,

mike

well, got my ATI balancer, similar to yours Sean94Z, but looks slightly different. its a nice looking piece, but i have some concerns that i think will end up forcing me to send it back :-( i will have to get some pics and talk to ATI tech probably.

first, i liked that my fluidampr lined up the blower pulley perfect as far as depth. I never had problems tossing blower belts with my new tensioner. i see what might look like a problem with the ATI. its about 1/4" or slightly more taller. i don't want belt problems and once you install the balancer to see how it lines up, you can't return it per the instructions. just comparing the two leaves me with definate concerns.

second, the side of the procharger 12 rib crank pulley that mates with the balancer is flat with the exception of a small snout that penetrates into the balancer to help line it up and provide support other than the bolts. the snout is the same size of the SBC snout. the side of the fluidampr that mates to the procharger pulley has a hole the size of the snout opening. this ATI balancer two piece has a hole much bigger (close the BBC snout). the ATI hub side ID is SBC. this will mean the pulley can flex more, move around, and potentially put a lot more stress on the 3 bolts its mounted with. not sure how long that would last.

it just looks like it might be asking for problems.. Sean94Z do you recognize these same concerns? :confused:

I was thinking about giving InnovativeWest a call for a custom balancer matching the fluidampr exactly in dimensions with the exception of the BBC OD hub size.

am i over analyzing this?

thanks,

mike

I don't know about the belt lining up. I still dont have my engine back from the enginer builder to try anything yet.. I Have parts all over the place, and haven't really compared the exact sizes ..

I understand what you are saying about the ati supercharger pulley and the new balancer. It is not like that on mine.. I have a damper, then an aluminum spacer which fits PERFECTLY inside the damper hole and then the supercharger pulley fits on top of the spacer and that fits perfectly inside the spacer..

Sorry,but it's too hard for me to say, I Dont have anything in front of me and havent installed it yet either to check out the spacing ..

--Sean

here is a pic of what i am talking about for those that might not be able to picture it.

http://msm.cz28.com/damp_f.jpg

I may have missed something but that hub looks like the one sold by ASP. They charge $100 for theirs.

Never seen the one by ASP, this is an ATI Piece.. But, that would piss me off is ASP sells one exactly the same for $50 cheaper :D