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Put a cam in our 2004 Corvette a couple years ago. At the time I used a nice puller to pull the balancer and an install tool to reinstall an UD pulley and replaced the torque to yield GM bolt with an ARP bolt. Everything went together fine and car has run well for a couple years.
Fast forward to today. I'm tearing it down again in the car to install a more aggressive cam. As I was removing the ARP balancer bolt today it seemed to be coming out fine but toward the end it snugged up a little but I kept on turning. This is what came out:
What happened and am I screwed (pardon the pun!) I'm going to chase the crank with a tap (good idea Ron ... thanks!) and see if it will clean up and if the OEM bolt will thread back in. If so I'll order a new ARP bolt and button it up. If not I guess the engine has to come out and get torn apart?
It looks to me like part of the ARP bolt is still in the crank. Have you got an OEM bolt to compare bolt lengths with. You could use a small dowel rod to insert into the crank and find where it bottoms out. Mark the dowel and measure the insertion length. I have a stock bolt and it's exactly 4.5" long from shoulder to tip. Threads are 2.5". If you have less in either measurement - there's something still in the crank.
It looks to me like part of the ARP bolt is still in the crank. Have you got an OEM bolt to compare bolt lengths with. You could use a small dowel rod to insert into the crank and find where it bottoms out. Mark the dowel and measure the insertion length. I have a stock bolt and it's exactly 4.5" long from shoulder to tip. Threads are 2.5". If you have less in either measurement - there's something still in the crank.
I don't think a piece broke off in there. I believe it just chewed the threads off the end of the bolt but don't know why it would do that. I'm going to pull the balancer and run a tap in there to see if the crank threads are shot. Before I do I'll insert a small dowel to be sure it's clear which I think it is.
The only time I've ever seen a bolt lose threads like that was when I had a crank that had the threads end before the hole did and the bolt went 1/4" past the threaded portion.
The only time I've ever seen a bolt lose threads like that was when I had a crank that had the threads end before the hole did and the bolt went 1/4" past the threaded portion.
That is a possibility. If that is the case I wonder if the crank is ok?
Crank must not be threaded all the way. Get the correct size bottom tap and run it all the way in a few times. Get a new ARP bolt too.
Bottom tap won't bite. OEM bolt is the exact same as the ARP replacement. Threads damage must be on the front. I can't get the tap to to catch. Going to try to put a helicoli in it.
Bottom tap won't bite. OEM bolt is the exact same as the ARP replacement. Threads damage must be on the front. I can't get the tap to to catch. Going to try to put a helicoli in it.
Try a regular tap to get the first threads clean. They have a long lead to start them.
i had this happen to me on a gen 1. i was being a dummy and screwed up the first 4-5 threads with the balancer puller. i gouged them out with a carbide burr and got a tap to start. there's enough engagement---especially on an LS---that the loss of 10% isn't gonna be an issue.
Just talked to ARP. Don't remember the gentleman's name but what a nice guy! He said the threads from the factory on the crank can be crude at best and it's not uncommon for GM and ARP bolts to freeze up. He is sending me a replacement bolt at no cost which is nice. He suggested I use my screwed up ARP bolt, with lots of lube, and see if I can smooth down the damaged area and use it as a thread chaser (vs. a tap which is different as he explained it to me) to get the threads started again. It's worth a try.
Be careful using a true bottom tap as that is designed with the pitch of it's threads to cut. See if you can find a thread chaser to simply clean them out. And then when you're ready to install BE SURE to use a good balancer installation tool and lots of lube on your bolt.
I'm going to use my bolt to see if I can start the threads again and if not I'll see if I can locate a thread chaser. I'm going to do everything I can to try and NOT drill this out to a larger size.
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what broke ... with picture 
