WS6FTW

My friend has a 402 in his vette. His crank bolt has backed out now for the second time while driving. First time it was while he was on the dyno. He has torqued it to the right ftlb, and the second time with the new bolt I beleive he even put locktite on it. So, what can he do to stop this from happening? Or what is causing this to happen?

GOaT Cheese

The bolt needs to be new everytime. And how is he torquing it? GM procedure, or some goofy aftermarket procedure? If GM procedure he is using ALL the proper "J" tools to do it, or is he short cutting it some way?

ls1itldo

iTrader: (30)

No need to change the bolt, it just needs to be pinned. No more problems.

Jake@EPP

If you are using the torque to yelid bolt then you will need to use a new one everytime it is torqued. With the TTY bolt you need a 15/16 socket and a long wratchet with cheater bar on it. Torque pretty much as tight as you can go, there shouldnt be a need for locktight if done right. Now if your using the ARP bolt, then just follow there instructions.

WS6FTW

As far as I know he has been using a new bolt everytime. Is the torque spec on it 240ftlb? What is the GM procedure?

GOaT Cheese

GM procedure requires several steps. First you must remove the starter and lock the flywheel with tool J-42386A, then install balancer using tool J-41665. Install balancer 2.40 - 4.48 mm short of being flush with the end of the crank snout. Then using the OLD bolt, tighten to 240 ft.lbs., remove and discard OLD bolt. Install new bolt and torque to 37 ft.lbs. for first pass, then tighten an addition 140 degrees, not pounds, but degrees. If you stick to this procedure exactly, the bolt will not come loose.

WS6FTW

Wow. Didn't know that. Thanks for clarifying. How expensive are these tools to buy/rent.

04Yukonxl

I've done several of these without any problems and without the "J" tools. If it's an automatic, you need to use a screw driver to hold the flywheel, if it's a manual, put the car in 4th gear. Drive the pulley on using the old bolt until it's tight. remove the old bolt, install the new bolt and then torque to 37 ft. lbs. Use a sharpie to put a horizontal stripe on the head of the new bolt and make sure you have rotated it 140 degrees, this is the torque to yield step. If you didn't do this last step, your bolt will come out.

Camaro_Zach

iTrader: (19)

new bolts are about $3-$5 from gm

mikep2002

iTrader: (10)

If your running a 402 I would just pin the crank and be done with it. Why bother playing stupid games with it. I had mine come loose on the dyno under boost what an interesting dyno sheet. Your really gonna be depressed if it tears the crank seal on the timing cover. Bob over at epp has the kits.

Its alot of work to move the steering rack and everything else. I think your asking for it to happen again by not pinning the crank.

michael402z06

iTrader: (15)

where can you get the stuff to pin the crank??

andereck

Kinda makes you wonder why the old way needed to be "improved" huh? I have never had a Gen1 balancer bolt or balancer come loose.

TTY is risky and unnecessary for that application. Head bolts I can see the benifit, but a balancer bolt? Must have done some hiring ifrom the Dearborn area.

Hell Chevy didn't even use a bolt until '67-'68.

XLR8NSS

iTrader: (4)

I'm with you, why couldn't they just have a keyed crank from the factory.

Interference fit balancer with a TTY bolt =

Best thing to do is get a pin kit and never worry about the crank spinning again.

Magnacharger or any of their dealers sells a kit to pin the crank.

XLR8NSS

iTrader: (4)

It happens when the interference fit between the crank snout and pulley is not enough to keep the pulley from spinning. This can be caused by extra load being placed on the drive system like when you put a belt driven blower on. It can also be caused by high hp engines accelerating too fast for the crank pulley fit to keep up with.

When the pulley slips do to whatever situation it is effectively like a wrench that just backs the balancer bolt right out since the bolt is in contact with it. The crank is spinning clockwise(looking from front), the balancer is slipping(effectively counterclockwise), the bolt is right hand thread so lefty loosey.

It's kinda like what happens when a tire spins on the rim.

GOaT Cheese

Ya, I don't know why they changed the basic design. Or just put in a goddamned keyway.

Bandit28

iTrader: (28)

You dont have to pin it, and it souldnt back out, even when you bap it on with an impact

garrettpen

Who makes a pin kit?

GOaT Cheese

Your right, it shouldn't. But in all honesty, every one of those things I just hit with a gun has come loose. Now I use the proper procedure every time.

andereck

ATI
and
ATI

Accessible Technologies Inc
&
ATI Performance Products

mwalls54

well i am going thru the after math of a crank spinning. i just put a new cam in my 408 and i broke it in then i did a wot run and at 6500 the pully started to slip which led the bolt to come out. made the pully wobble and it messed up the pulley and it was a asp under drive pulley. its shot now, so i got a stock pulley and bought a new bolt. same thing happened, bolt backed out and pulley messed up. well i picked up another stock pulley and was putting it on when my crank bolt broke off in the crank, so now i have to have that fixed. and i am having a hard time getting it done.
so the moral to this story is if you are running 450+hp then you need to pin the crank.