1 FMF

iTrader: (1)

hi,
from reading here and there, and hearing of crank bolt breakages and other horror stories, I gather the harmonic damper is bolted onto the end of the crankshaft and the crank is not keyed. And you tighten the crank bolt to some ridiculous torque spec like 200 lb-ft to hold the pulley on.

if that is correct, why is the torque value so high and why do it that way?

i am guessing there is a flange on the nose of the crank that the damper pulley gets pushed up against?

and the huge torque value of the crank damper bolt is to clamp it against the crank hard enough so it doesn't spin, because it is not keyed?

just trying to understand how the crank damper pulley mounts, and why. I'm guessing it's a manufacturing cost savings by having a keyless crank?
thanks

SLP Firehawk

iTrader: (9)

the pulley kind of gets pressed on the flang or " snout" of the crankshaft. the reason u hear storys about putting the pulley back on is because its hard to get it to go back on the snout and it needs some good pressure and the stock crank bolt is not long enough to install the pulley with out damaging the threads on the crankshaft. that is why everyone highly recommends a longer crank bolt so there is not a high chance of messing up the crankshaft threads however that bolt is for installation purposes only you need to buy another stock crank bolt from the dealer oh yeah i forgot to mention the installation bolt gets torqued to 200 foot pounds or around there

1 FMF

iTrader: (1)

thanks, i understand the reason of how the threads are stripped now.

just for clarification, if the damper is not keyed onto the crank what keeps it from spinning? It is the clamping force of the bolt at around 200 lb-ft which is pushing the damper against a step (increase in diameter) on the crank on the backside of the damper, which is why that crank bolt torque value is so high?

Grimes

iTrader: (3)

I think it's a combination of the bolt and the interference fit between the crank snout and the balancer.

massls1guy

iTrader: (9)

It's called an 'interference fit'. There is no step on the crank. The bore size of the balancer is a little bit smaller than the diameter of the crank. The card that came with my underdrive pulley has specs on the fit:
http://www.putfile.com/pic.php?img=7575622

I believe the purpose of the bolt is to keep the pulley, oil drive & cam gear pressed home against the crank.

If you install a belt driven supercharger on an LSx they suggest that you 'pin the pulley to the crank'. There was an article in GMHTP where they did it on a GTO with a centrifugal supercharger. It's essentially adding a key to it.

vettenuts

iTrader: (4)

Don't use a longer bolt, it overloads the threads.

Massls1guy is correct, the bolt is providing the force required to spin the drive belts, oil pump and the timing sprockets. The bolt preload is set by GM to provide the necessary forces to do this. There is no torque value with the stock bolt, it is a rotation through a specific angle which provides a more accurate method of providing the correct preload. If you deviate from the GM procedure, including the removal and installation methods and tools, you do so at great risk.

SLP Firehawk

iTrader: (9)

how do you go about installing the pulley back on the snout?
everyone told me to use a longer crank bolt to install it. either that or i would heat up the pulley but not sure if i want to do that to a brand new underdrive pulley

rpmauto

iTrader: (14)

the factory bolt is a tty bolt.

Weezzer

You need a piece of all thread (with lots of washers), its 16 mm by 2 pitch (two mm per thread, one nut revolution =0.080" axial movement.

The pully needs to be on the crank a certain distance, if I recall correctly on my 02 the crank snout face needs to be recessed into the hub between 0.094" to 0.176". GM formulated it will take 240 ft lbs for the bolt to "pull" the hub into the correct position. In my Helms manual it says once the bolt is torqued to 240 ft*lbs remove the bolt and check the depth. If the depth is not in the range you are to repeat the 240 ft*lbs torque.

Once the hub is in the correct position you take your new crank bolt, torque it to 37 ft*lbs then turn the bolt 140 degrees further.

If you get some all thread and can use a depth mic or are good with a dial caliper you don't need to torque it to the 240 ft*lbs. Just use the all thread and be sure the hub is mounted within the required specs distance(remenber one turn of the nut or bolt makes the hub move 0.080" axially), then you can simply do the final torque sequence and try to turn it an extra 140 degrees.....I say try to turn it another 140 degrees but even with the emergency brake on, the tranny in forth, and someone standing on the brake pedal I could only get about 95 degrees then the car would start moving....

Weezzer

TTY simply means your purposely taking the bolt thru the elastic range and into the plastic range of deformation.
All bolts can be torque to yield bolts if you over-torque them....assuming the parent (tapped) material doesn't strip first.
Once into the plastic range of deformation the bolt gives you a higher clamping force but its a one shot deal. Once you remove the bolt you've weakened the bolts head clamping strength. Like I said..its a one shot deal.

There is nothing special about a TTY bolt....

Weezzer

I disagree, while the balancer is driving the drive belts -the crank thru the engine is providing the force to spin the oil pump and the timing sprockets.
The bolt simply provides the force to hold the balancer into position on the crank.
Since the the oil pump is driven by the same sprocket that drives the timing gears and this sproket is keyed on the crank snout. The balancer never touches it - I just don't see how you can come to the conclusion above.
If this was the case you'd pull the balancer tight against the sprocket and the oil pump and you'd not need to worry about the position of the balancer from the end of the crank snout.

vettenuts

iTrader: (4)

Actually, the key is an index only. I ran some numbers and didn't like what I found on the aftermarket crank sprocket since the key engagement is 3/8". I spoke with Cloyes tech support and they confirmed it is the load from the bolt that also hold the pulley in place that drives the whole thing. The key is not designed to handle the loads, especially when you examine an aftermarket timing set. The balancer is pressing the crank sprocket of the timing set into a chamfer on the crankshaft.

larrygto

iTrader: (3)

Stupid question Where would be a good place to find all thread? I have read you can get longer bolts a John Dear dealers is this true?

massls1guy

iTrader: (9)

I bought this install tool from a member here. It worked very well, no problems.
https://ls1tech.com/forums/removed-locked-thread-graveyard/391883-new-crank-dampener-installation-tool-pics.html

Weezzer

Perhaps this is true on an after market set up, but nothing was mentioned by the OP about an after market set up - but for stock set up I stand by my observations.

Weezzer

[QUOTE=larrygto;8592895]Stupid question Where would be a good place to find all thread? ...QUOTE]

A good old-fashioned Hard Ware store should already have it in stock.
If your lucky you can find it in a one foot stick, more than likely it will be a 3 foot stick and be around 12-15 bucks.

Andy1

I suppose it's possible that there's some variation to the interference fit to where some dampeners are more difficult to install than others. In my particular case, I heated my dampener to 180-200 degrees and it nearly slipped right into place except for perhaps the last 3/8". I gently tapped on the dampener hub with a short aluminum bar and hammer, and it easily seated without the need for a special installation tool.

Andy1

s346k

iTrader: (4)

set that mug in the oven on 300* for awhile. it will go on like butter.

Andy1

Guess I should have added that you now need to torque the bolt to the proper spec.

Andy1

99mongooSS

iTrader: (4)

a big hammer and a 2x4 on the pulley and then once its seated on enough install new bolt and crank down. be care full to get it on there a ways first cus i didn't and stripped the threads in my crank then had to go and find a 16 mm thread tap to re thread mine.