The Stovebolt Site Forums The Shop Area Engine Shop Sheared off crank bolt (58 283)

I was getting ready to rotatethe 283 in my 58 to find/verify TDC relative to the timing marks on the dampener when I discovered that the dampener bolt was previously sheared off about 2/3 of a thread below the surface.

I put it in gear and just pushed the truck to rotate the engine and determined that the stamped mark on the dampener is in the correct location, so it has not spun.

I am trying to decide how worried I should be about the bolt. It is (as far as I know) bone stock except the HEI distributor. The only accessories are the water pump and alternator. I put an electric fan on, so that is a little bit less load on the belt.

I don't really want to pull the engine to fix that right now since I am just getting it on the road for the first time.

In y'all's experience, what do you think the chances are of it walking itself off puttering around town?

Pretty low. I had a 283 in a 1957 and a 1958 Bel-Air and neither of them had a retaining bolt...if that's what you're asking.

Edit...you know there is a key in there that keeps the harmonic balancer from rotating...

Yes, somebody drilled and tapped it for a bolt then probably used the bolt to press the dampener on the crank instead of using the proper installation tool. It will have to be drilled out and use a easy-out to remove it. possibly a left hand drill bit may work as long as it is not bottomed out in the crankshaft hole.

Yeah, I know there is (supposed to be) a key, but I have also seen them get sheared off.

Personally, I have never had a dampener that I could remove without a pretty stout puller so it *seemed* low risk to me, but I wanted a second opinion anyway.

Maybe I've just been lucky but I've never seen one sheared off in a dampener. A friend had a 2 stroke Lambretta motorscooter that used puny aluminum keys for the flywheel/magneto. Occasionally it would shear one and then spin around and get the timing so retarded it would run backwards. Yes, I know. Sounds really strange but it can happen.

The balancer bolt on my '56 Cadillac broke a few years back and the balancer walked itself to the end of the crank. Luckily the fan started hitting the pulley and I pulled right over.

I bought a left handed drill bit and just drilling the bolt was enough for it to remove the remaining part. I didn't even need to use the Easy-Out.

I reinstalled it with red Loctite on the shaft and a new grade 5 bolt.

I was able to gain access by removing the radiator and ac condenser.

My '57 2 ton has the original 283 with no damper bolt, I pull the damper when I replaced the cam, lifters, chain and sprockets. Re-installed everything as it came from Chevrolet, been driving it for 7 years at high RPM without issues.

I would definitely use some Loctite as added insurance with or without a bolt.

G.M. Save lots of money not putting damper bolts on many of their engines.

If any 283s came from the factory with a bolt-on damper, I'm not aware of it, and I started doing engine work in 1958. They're a press fit. The first engines that came with damper bolts came out in the mid to late 1970s, mostly late model 327s and 350s. If you have a 283 with a bolt in the crankshaft snout, it has been installed (and probably overtorqued) by some shade tree wrench jockey long after it left the factory. The balancer/damper is keyed to the crankshaft, so it cannot possibly spin out of position. The outer ring of the balancer can lose its grip on the rubber damper that holds the two pieces in alignment, and the timing mark can move that way, but the center hub cannot move unless the Woodruff key shears off. I don't think I've ever seen that happen in 60+ years of making a living fixing everything that rolls, floats, or flies, and 30+ years of teaching the trade.
Jerry

The 283s did not have damper bolts, same as 235 and 261 cranks. So if your 283 crank has a bolt, it was drilled and tapped for a bolt at some point in its life. I drill and tap all of my 235 and 261 cranks as a matter of course so I can use a real damper installer instead of a block of wood and a big hammer.

A lot of guys will use this bolt to turn the motor around. And a lot of the bolts will stretch and brake as a result. So use the correct tool for turning the balancer.

So first thing, are you 100 percent sure yours was drilled and tapped for a bolt?

If you are 100 percent sure, you might try drilling the center for threads, largest bolt you think you can get away with, tap for threads, red lock tite and after that stuff hardens up, see if you can back it out with the broken bolt.

Another possibility, the bolt was probably one for a small block Chevy, 7/16-20. Drill the entire thing out for the larger big block bolt, tap and install a big block size bolt 1/2-20.

If it turns out it was not drilled for a bolt, and you want to drill and tap for one, here is a tool to help with that process.

He also sells one for the larger big block size bolt.

https://mrhotrod6.com/products/cran...t-sbc-283-and-327-cid?variant=1142530117

The casting numbers indicate that the block is a 58 283. That being 66 years ago, who really knows what is going on now. At least as far down as the rockers and valley it appears stock.

I ran a borescope in the center of the pulley to see what was going on when I didn't see a bolt head and it sure looked like a sheared bolt.

I assume that the end of the crank would have been machined and not left as-cast? Picturing it in my head, it *could* have been a rough cast surface, but I don't think so.

I think I will just run it as-is and keep an eye on it.

Thanks for the info!

I actually saw a "proper" installation tool once for these older pressed on balancer engines. I wish I knew where that was. Has anyone seen them? Maybe someday I'll build one.

Oh there was mention of "RED" Loctite, I wouldn't do that on any bolt that I wish to ever remove, read the label its supposed to be permanent, or requiring a bunch of heat to soften it to remove the bolt.

Any type of LocTite (including red) softens up at around 500 degrees F. A torch is your friend when you think you're about to shear off a bolt or round off the head if it doesn't respond to normal disassembly methods. We assembled racing engine connecting rods with red LocTite.
Jerry