Hey guys... it's been a while. Sorry to pop back in on a bad note.

I blew out my crank threads this weekend. Story below.

Anyone else do this? What repair method did you go with, Heli-Coil, or just retap to a larger size? (3/4x16? 3/4x10?)

If heli-coil: Did you go with one of their kits? How hard was the install? How much room was there to work with the drill and tap? Was it easy to get things dead-nuts-on? (Straight?) How did you set the depth of the coil? Was the supplied drill and tap long enough to get down to the correct depth?

If tapped to larger size: Did you have to drill? What length bolt did you end up using? What size/pitch hardware? How close to the end of the snout did the tap start to bite?

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Long story short - Longer crank bolt method doesn't always work. It mangled the threads. .....Things got hard when I was seating the pully. I was thinking everything was hard because I didn't pre-heat the pulley like I did the last two cam-swaps. I got the bolt out, and the threads were mangled. I thought the bolt failed. It wasn't just that. It mangled the crank threads enough so that I blew out them out when I had about 2mm left to go with seating the pully with the stock bolt. Yeah, I should have gone straight for a pulley-install rod prior to that, but I was naive. I thought the longer crank bolt was the only thing that failed.

I ground down one of my long bolts to a cheap thread chaser, cut it to the appropriate lengh of the threads in the hole, and cleaned out the remmaining untouched threads back there. I cut down another long bolt to the same length, and was able to quite easily seat the pulley. I threw some locktite on the bolt, and was able to put some grunt into a 3' breaker... and so far it held.

The truck is up and running, but I don't trust my 'fix'. I used three washers stacked behind the long crank bolt, and they bend in from the torque. I don't trust them with holding the pulley back, and I don't trust them to stop the pulley from spinning and backing the bolt out. What do you all think of this... is it good enough, or should I do it right?

Then there is the issue of 'doing it right'. At this piont, I'm afraid to touch ANYTHING in the truck... (but I could be convinced to.) Do you think this is a job for a machine shop, or a regular automotive place?

Regardless... I'm going to need to set myself up with a pulley install rod so I don't do this crap 'next' time around.

Thanks,
-marc

 

For now keep an eye on it ,you might put 2 marks 1 on the bolt 1 on the pulley aligned,if it moves you can tell by a glance.

 

Good call, thanks, I was going to do that tonight before some test-driving.

So far, the thing is holding up okay in the driveway after a few heat-cycles, a bunch of revving, and with the AC bumping on and off.

 

not sure how to but a heli coil should work i have seen mech at work heli cummins main bolts and those are 250ftlb bolts.glad i didnt read this before i did mine.sorry to hear about this.

 

Man that sucks. Good luck. Personally (and I know its not right) I would keep a close eye on it for a few days....weeks maybe before I trusted, but if you decide to do another cam in that motor, I think You'll probably run into problems. The back threads will probably hold, but I know its got to be making you nervous

 

Helicoil would be the best fix at this point. Not sure if it will be needed unless you plan on doing another cam swap. If you were able to seat the pulley using a breaker bar, I'd expect you have enough torque on them to hold. Not sure about you using washers though. Mark the bolt as Gonzo suggested. Also, get a good measurement for the distance between the back of the crank pulley and the front cover and check it periodically.

 

Thanks guys... I threw the stock cam back in, and at this point, that should be the last cam to go in there.

What's really sucking right now is that I've got a camping trip scheduled to leave this coming Sunday. Towing our 5,000lb camper about 150 miles. I'm "this" close to cancelling it.

The truck is going in a shop Thursday morning. From what I told them, they seemed fairly content with my 'fix', but they're going to take it apart and "take a look at it". They were not keen on the heli-coil idea, but said they could do it. They said they've got a guy there that loves this weird/techical stuff.

 

Sorry about your trouble, but glad to see you back around here!

 

Yeah, I really don't like the washers... I think they're just regular steel. I'm guessing they're just under 3/16" thick (4mm?). All three, together, pulled in a bit.

What's the strongest type of steel, stainless? I'd order something up now, but I don't know the OD of the washers I have now, or the ID of the recess in the pulley.

 

Hey Boss...

That isn't ever a good feeling when you torque it up and just when it should get tight, things get loose....

I don't know that I'd let anybody take it apart, especially if it was holding. In my opinion, I wouldn't run the risk of HAVING to helicoil it (or some other solution, like replacing the crank) just to take it apart and inspect it. That is likely to cause more trouble. Either its holding good or its not (witness marks are spinning). I wouldn't be going in there looking for trouble (because you might just find it!)

As far as washers go, stainless isn't the strongest. Stainless bolts are little weaker than grade 5 bolts, washers are the same basic deal. If you want really strong, you'll want to use Grade 8 washers or some of the specialty products (like hardened and ground washers).

Again, I'd still say mark it, inspect it, and unless it gives you trouble, leave it alone.

Might I suggest a Good Sam roadside assistance membership?

'Dreamin'