how important is the key that lines the damper up with the crank? mine sheared off and left a big pit in the crank and i don't want to change the crank or put a new engine in. the timing mark was already off so that wont realy matter if it is lighed up for now. will the pressure from the bolt holding it on be enough to hold it in place? its a 67 283 that was drilled for a bolt and is a press fit design.

 

i'd say the key is right at 100% needed part. look into using devcon or something similar to make the repair if you don't want to swap cranks.

 

whats devcon, and how do you use it? will it be strong enough?

 

Yup, pretty essential, the natural job of the damper (damping vibration) will cause it to walk without one. Even the old 283s without a bolt, had a key; that's how necessary it is.

Devcon is a brand of epoxy.

Expect trouble from that part of your motor from now until the day it dies. I've never known any repair, other than welding up and re-cutting the keyway, to be long-term successful. The repair is costly enough that the crank is usually not worth saving, because a core is cheaper than the repair.

You might want to figure out why it sheared the key, and make sure it doesn't happen again. And put on your calendar to inspect and/or tighten the bolt every week or 2. With the key gone, when the bolt backs out (it's "when" not "if") the balancer will launch itself, perhaps through the radiator, or hood, or water pump, or who knows what; and of course it will be more prone to happen at high RPMs, just when it is the most dangerous to yourself, your car, and everyone and everything else in the vicinity.

Good luck!!!

 

If you have a welder or know someone, they could weld the balancer to the crank. Big down fall of this is crank and balancer will not be usable in future rebuild, of course your crank is shot right now, so no biggie, right.

 

i found the problem i think. the damper had a woble in it so when the belts and all were pulling on it at high speeds it stripped the bolt and moved it out about 1 thread making it come off of the crank a little bit. just enough to put all the pressure on the key. luckily we tapped the hole deep enough to put a longer bolt in and have it hold. i think a new balancer and some devcon will hold it on long enough to be able to get something like a 350 in before summer.

 

can you buy that devcon at someplace like autozone? if not where can you buy it?

edit:i'l try to get some pics tonight

 

Dang. When I did the front seal on my car I remember as I was putting the damper back in, the key just came out of the groove with only a slight touch. The damper went in fine with the key there, but I didn't know it was supposed to stay attatched to the crank as one unit.

 

I'd only do this as a temporary fix but. . . you could drill a 1/4" hole into the end of the crank and balancer, getting as even as possible, (as much crank as you do balancer) and then tap it for a 3/4" long 5/16x18" set screw. Make sure the balancer is pulled all the way onto the crankshaft first and lined up as close as possible to the original keyway. Then, install the pulley and the dampner bolt and tighten it. Matter of fact, you could put two of them in there 180° apart. It'll bet it will hold it quite a while.

Just a suggestion.

 

what i'm probably going to do is cut another slot for a key about 180* on the other side. i'l probably put some epoxy in the slot to hold the key tighter incase there is any play. that should work just as well as the original if i get it close enough. i'l also move the timing mark on the balancer to the other side.

 

i'm also going to tack weld it in a few places to make sure it stays put and i can grind them off if i want to take the damper off.

 

Sure. Just remember that you're working with castings. And a rubber ring, so forget about a torch or the damper will be shot.

Another possibility is a new key - a round one. There are several industrial applications that use round keys instead of square or Woodruff, and in a helluva lot higher stress than any thirty gasoline engines together would ever see. The repair takes a little preparation. Drill small (about 1/8") longitudal hole at the intersection of the crank snout and the balancer hub (so that half of the hole is in each part). Drill about 1½" deep. If the hole is straight and where you want it, step the drill size up to about 3/16-13/64". Using a small tapered reamer (about a Morse 6 or 7) and cutting fluid, start reaming up the hole for a taper pin.

Check the size frequently to make sure you don't over ream. When it's close, insert a 6 or 7 taper pin with a tapped end (for removing with a slide hammer) and lightly tap it in place so that it's fairly well seated. Mark the depth, then remove it. Cut the pin just slightly longer than the marking so that the heavy washer under the crank center bolt holds it in place. Tap in the pin and finish assembly.

When you're ready to pull the balancer hub, rememnber to pull the taper pin first. You won't be able to use the crank again, but it's already trashed. You COULD re-use the damper, but I wouldn't - especially if you're changing strokes.

You can find tapered reamers and taper pins (by the bag full) at any industrial power transmission supplier or general supplier like McMaster, Fatenal, Grainer, or MSC.

If you were really cheap and dirty, you could drill and tap two holes at the intersectio at end of the crank, just as you would in a taper bushing. There are plenty of 200 HP and large electric motors with couplings and sheaves attached that way, and they see 200+HP all at once - as sonn as the power is turned on. .

 

the way i was thinking was just using a stock key and cutting another slot just like stock. i'l use a dremel with about 6 thin cutoff wheels stacked up. i'l cut it to about stock depth then remove a little from the sides to make it fit just right. i tryed it on a piece of scrap metal and it works pretty good. it takes some time cutting but i'm going to take my time on something like this anyway. with some epoxy to hold it on place better i think it will work about as good as stock.

 

And I guess you'll have to use some timing tape or whatever to get a "correct" timing mark...

This sorta happened to me, when I was doing my timing chain- I tried to use the center crank bolt to draw the balancer on- yep, snapped the bolt off right at the crank snout. Took it to my mechanic, he arc welded the balancer to the crank for me... it's been that way since '98.

 

Had a balancer literally FALL OFF the front of the crank on an engine recently (no center bolt was used by whoever built the motor- go figure). It tore he11 outta the crank keyway as the balancer fell of the front of a running motor.

I took one look at it and concluded: I'll never get this fixed right. New crank time.

Suckes thorwing an otherwise perfect crank in the trash but that's what I did.

The idea of drilling and tapping a bolt of some kind into the crank snout through the balancer's inner ring probably has merit but use something STRONG- grade 8. The stock key has a LOT of surface area to transfer force between the crank and the balancer versus a small bolt.

 

I might not have clearly described the method, so this may help illustrate it:

 

thx vader, that looks like it would work pretty good. i'l talk to my dad about that and se what he thinks.

 

that would be kinda hard to get a hole in the middle though on mine. the edge of the damper sits about 1" off of the crank when its all the way on.