Crank hub - Roots
 

I run an old Ed Pink 8-71 race blower on my GTO and a couple nights ago at cruise night I noticed the hub had slid out and my belt was dancing around. The hub is a BDS unit for pontiacs and I was using the factory crank bolt to hold it. It looks like it became loose and the hub was working back and forth on the key causing it to wallow out the keyway in the crank and then the bolt broke and it split the crank hub up through the keyway.

Since I am now having to change out a perfectly good crank is there a better hub or system than what I had? If this had been an exepensive forged or billet I would be really ticked but right now I am “only” looking at about $1200 to fix :(

Double key and use a stud instead of a bolt.

Cant you just replace there snout of your crank?
I use loctite (blue) on my damper bolt.....never had one come loose. NOW I've broken the hub on my damper couple of times BUT I am a Bracket Racer so me getting off and on my throttle a couple of times a run is a BAD thing.


GTO George

Never heard of replacing a snout! It’s a factory 455 crank...

It was double keyed. I like the stud idea!

CAST crank.......that would be the problem!



GTO George

This is an area we have put considerable time and effort into and so far, no failures. We use a double 1/4" keyway with hardened steel keys. We use an RCD blower hub for a 385 series Ford application that is NOT fully finished. You need to call them and tell them exactly what you are doing and they will pull a Ford unit off line before final hone which will give you a nice .001-.0015 press fit on a Pontiac crankshaft. Then we use a hard steel very thick custom step washer Eric designed but can be made fairly easily on a lathe. PM me and I can scan and send you a blueprint for the washer. Then we use an L9 bolt tightened to 230 Ft. Lbs. to hold it all together. So far, it has been a very simple and reliable set-up. I have the bolts and blueprint for the washer if you decide to go this route. As George said, if it was a billet or forged crank, I would consider cutting the nose off and putting a new one on. Cast N, crank, time for a new one.

Really liked the stud idea but was unable to find the correct size made from the correct material. Talked to ARP a couple of times and it was going to cost upward of $500.00 to make a single stud/nut combination happen. So we switched gears and went with an L9 bolt from McMaster Carr for about $5.00. Has worked fine. Stud would probably be better, but the weird Pontiac size complicates matters.

Having ARP make you something it like BEND over and here it comes! I tried and to get them to make a better grade head stud........damn it was a lot and then once we settled on a price they raised it on me! Seriously the Bolt they (ARP) make for the crank should be good enough...........i think his hub cracked at the keyway.


GTO George

FYI......if a person is getting on and off the gas peddle during a 1/4 mile (or a blast down the e-way) attempt that will crack a hub or worse in a heart beat! Its that yank from the blower belt/blower.


GTO George

The ARP crank bolt was way too short for our deal with the RCD hub, which is why we went with an L9 bolt from McMaster Carr. I had to buy a box of like 15 or 20 of them so I have a few spares if the OP needs one. He will have to make our super thick step washer for the whole deal to be the right length though. Custom one-off parts like the head studs you wanted or a special 5/8" fine thread stud can get crazy expensive. Places like ARP are set up for big production runs. Little odd requests, just seem to upset them.
Trivia: When Eric designed our billet Ram Air V heads, he designed them around ARP's EXISTING 9/16" studs to avoid the custom fastener issue. That was a smart move.

If i’d known then what I know now I’d went with 9/16” head studs!
Diesels and Jap junks have better head studs!

GTO George

George,
If you were to convert to 9/16" studs, it's not too late block wise. You can direct tap a 1/2" tapped block to 9/16" You won't quite get the 75% thread engagement, but they will certainly hold an aluminum head. Since you run the KRE heads, and I know little about them, you would want to give them a call. You have to make sure they have enough column thickness to support the larger studs and won'd crush or break through. I know early E heads DO NOT have enough material to support 9/16" studs, even with deep step washers. So a conversion may not be as easy at it seems. If you can do it, 9/16" studs give you MUCH more clamp load on the heads. We torque to 135 ft. lbs. But our heads are solid.

Solid heads thats cheating! :)


GTO George

George you mentioned foreign having better fasteners lol ...

13mm is just slightly over .5" (.5118")
14mm (.5511")slightly more and just barely less than .5625"(9/16)

Might be worth investigating.

Noooooo, I guess I need to spell it out.......”ARP” make better fasteners for jap junks and diesels the Pontiac’s!
Yes as always I’ve been way ahead of you on the other sizes, thank you.



GTO GEORGE

I agree with the above posts, your next crank definitely needs to be doubled keyed. I've replaced two snouts on my crank. The side load from the side-slinger blower is brutal when you're pedaling the car.

I have a crank support that is for sale that would help with that, but it would need to be modified for your application. Mark at Luhn Performance hooked it up for me!

Good luck with your car!:)

Hi, how can I get a couple of these bolts and instructions to make the step washer?

My crank was double keyed...lots of goosing it around on the street probably did the key ways in...need a better bolt setup...

Honest.....on.....off.....on......off the Loud Pedal is a BAD thing with a supercharger, crank snout does not like it!!!! I’m the only Pontiac out there Bracket Racing a Roots Blower, a Bracket Racers is ALWAYS on and off the Loud Pedal......it’s the nature of the beast!


GTO George