Keyway damage - what caused it, what prevents it ?
 

Built motor – crank was last at machine shop getting balanced and then installed by me. New keyway, new bolt, new Supermiata damper – torque wrenched on. Car ran great for about 20,000kms. I’d like to note that I had rev limit settings based on what I found on here. She did like to shoot a flame or 4 and a beautiful staccato sound that was especially nice in tunnels and when playing in the snow and on a few city 2nd gear corners etc etc. Keep the rev limiter in mind for later on.
Started to hear some sounds on start up – maybe rod or cams or VVT ?? Pulled the VVT plug and it sounded better – must be VVT. Car didn’t run as good – down on bottom end power and overall power but I attributed this to the VVT issues. . Sound came back a bit. Decided to pull motor to put in FM Stage 2 clutch (ACT HD slipping at 20psi) and I had a front main or oil pan leak and I wanted to get the sound sorted. Cam timing looked spot on, but at TDC the timing marks were about a cm or more off. Interesting. Pulled the damper and oh no!

What caused this? What can prevent it? Could the violent action of the rev limiter and the mass of a dampers sudden retardation start to work the keyway ?

BTW - I found a 90,000km 1.8 short block so I’m going to take that crank probably. Rather that than weld and machine the old keyway.

Insufficient or overtorqued crank bolt.

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My guess is not enough torque, not enough red loc tite. The ATI damper presses onto the snout, makes for a much less-prone-to-stripping-or-vibrating-loose keyway interface.

So does the supermiata damper.

Landrew did you use loctite?

i can't tell by the pics if the key way in the crank itself is worn but I would doubt it as the key itself is usally what wears as yours shows. I would do as mentioned above, new key and crank gear. What could have been the problem is the key itself design. I have built several motors and I grind the inner end of the key to match the curve machined into the crank. This does two things IMO. It gives the key a little more sitting in the crank key way groove but more importantly it gives the key a better chance of not binding the dampener when sliding on. The stock square end on the oem key design well not slide back down forward if it is too high by just a little which can give a false torque reading. Then when you run the motor it can vibrate forward and down in the crank grove and let the torgus value on the crank bolt loosen If the key is formed more to the grove in the crankshaft if it is say a little high in the crank at the rear it well tend ti slide down and forward in the crank as the dampener is installed if that makes sense. I have done this to several motors I have built and never had a problem and this is the way a lot of keys are in cranks on other manufacturers as they use the half moon design keys. I install the key with some rtv in the crank grove and let it set and then never seize the crank and key and the hub inside before pressing on. I use a old crank bolt to install the dampener and then install a different one that has never been used to install the dampener. I personally use ARP lube to get a truer torque reading on the threads and under the head of the crank bolt and when torqued to the 125 ft lbs if I remember the recommended specs correctly have never had a issue and mine gets tortured. As stated above it is important to shape that key to matche crank grove and allow it to be able to slide down level as the dampener is installed so you don't have the key bind.

I have never once in my life used red loctite on the crank bolt. What I do use is the proper OEM torque spec, and 100ft.lbs is not it. (99-05 Engine FSM specs 116-122ft.lbs, I use 120ft.lbs). Blue loctite is the appropriate compound.

That whole area looks really impressively terrible for 20,000km.

Also, how's the torque wrench. They lose calibration over time and especially if handled roughly. The ones in our factory are on an annual recalibration cycle. Critical fasteners like head bolts/nuts and this one should be torqued with your golden wrench, not the one you use for quick wheel lug checks at the track.

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Just to clarify: You're mad because he stated the OEM torque specification and proper loctite?

Red loctite can cause stripped threads and broken bolts when removed without heat. And heating the nose of my crankshaft is not my favorite thing to do if I'm doing a timing belt job.

Blue loctite and FSM spec is the way to go.

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Its not closed minded. You listed an incorrect value. On a bolt with a specified torque. He was just correcting it.

Incorrect information doesnt help anyone.

Wadded panties don't either.

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Are you done crying?
Red loctite seems fine until you need to remove that bolt later.

Bigass impact wrench turned to setting #3.

:scratch:

:spit:

What?

Why y'all looking at me like that?




j/k

I don't have time to sugar coat it for you. 100ft.lbs is wrong. The FSM says 116-122. You don't need any experience at all to read the FSM and use the right torque spec. Red loctite is wrong. It's a serviceable fastener which must be removed every ~60k miles for timing belt service. Red loctite is designed for permanent applications. "Remove every 6 years" is not permanent.

This has nothing to do with popularity or your perception of my ego or anything else. Torque specs are not subjective. You published incorrect info, I corrected you. I'm not going to waste my time tip-toeing around your feelings because you think that you deserve a participation trophy for your new ideas. If you don't like being told off for being wrong, be wrong less.

I've always used red loc tite, 272 I think, didn't know blue was the OEM spec. Either way never had a problem taking a bolt out, never used heat either. I use red on that bolt, the flywheel bolts, and converter bolts as I don't ever want those vibrating loose. Not surprised that OEM spec is not Red loc tite but ther'es plenty of non-OEM things folks do to engines when building them for high performance/racing.

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In racing sometime you have to go above-and-beyond for reliable fasteners. Turbo bolts are well covered here, folks run high end stuff to make sure fasteners work right. For a crank bolt stock spec is probably fine. Since I ran a SC back when I put that bolt on I torqued it to 150 and put red loc tite cause SC guys strip the keyway with extra loading a lot more often than other folks. And I ran a lot of boost and a big SC, so I was pullling 100+ hp off the crank to drive that blower. Probably overkill but better than a failure from that bolt vibrating loose or stripping the key. For a crank bolt I'd rather over than under tighten that bolt, since under torque is very likely going to end like it did for the OP here.

On my converter bolts, I torqued them to 40-50 ft*lbs (7/16 grade 8 bolts) and they vibrated loose in about 10 miles! After searching some drag racing forums, the known to work fix is 80-90 ft*lbs and lots of red loc-tite. I did that, problem solved. Have a couple thousand miles on it now and so far bolts haven't moved. For the curious, that's not factory spec because factory spec on those doesn't work reliably in a drag car.

Sure. Overtorquing is great until the bolt yields and then it fails.

Torque specs exist for a reason. Especially FSM torque specs.

FSM torque spec is actually 3 braps.

Also, re-using a crank bolt can sometimes lead to the above damage. It is a pain, but I always buy a new crank bolt when doing timing belt work.

Ditto. The FSM doesn't specify it as a TTY bolt, but I replace it (and the key) on every motor I build. The exceptions are on my own personal motors during maintenance, since I know the bolt was replaced and has never been overtorqued.

Fwiw it's a $9 bolt through Mazdacomp. I bought 2. Seems too easy to replace to mess around with.

This.

But I'm also the type that when I completely redid the entire suspension for '90 Track rat, every bushing/bolt/nut/washer was replaced with fresh.

Wise. The last issue I had with my suspension was a yielding eccentric bolt. Leads to all kinds of mischief.

Still waiting to see what the used crankshaft I'm after looks like. Going to get my wrench tested (for free!) I'll definitely be buying new hardware. Won't be for a few.eeeks at least.

Thanks for all the discussion.

It's hard to tell from the pics, but have you tried a new key in the crank yet? Cranks are pretty hard steel.

I have not tried that. I will pull the sprocket and take a better look.

Got some pictures of the used crank I'm thinking about using. Not sure that I like it. I see some grooves and wear on the oil seal surface and some bearing surfaces look rough? not to mention there is slight keyway wear as well. What do you think ?

I wouldn't use it. I'd find a good 1.8 to get a good crank out of. One that doesn't need any repairs can be found for probably 100 bucks. Maybe less if you find a good deal.

That's what I suspected - thanks..

Run away.

That keyway is already hosed. Why start out with bad when good ones are available?

Contact Partsgroup.com. They've always done alright by me.

http://partsgroup.com/part/1994-2005...00c-bp0611300c

That crank is a paperweight

I have always wondered why there is not a better field repair for this common problem.

I was thinking something similar to what they do for GM LS motors for superchargers. Like this:
Pinning the crank pulley - LS1GTO.com Forums

Thanks for the tips, its either look at the parts group crank and ship to Canada or perhaps, but probably not look at the pinning options available.

So you tried a new key in the crank and it wasn't a tight fit?

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well this is debatable.

That's not the only thing debatable in the post.

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Why are you the way that you are
I did what you suggested when I was 18 and poor, mostly out of necessity, and the timing was off again within a few weeks and the keyway went from worn to destroyed.
I'll give you 0.1 poscat for the TPB references, redeemable at a later date when you've earned the other 0.9.

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It's been to long, much to long. I found a solution but Im not sure everyone will share in its joy. Like Spock said in the Wrath of Khan "What do you think of my solution?
So in sharing my dilemma with the head tech at a shop one day he said why don't you just enlarge the crank slot and get a stepped keyway or enlarge the rest of the peripherals. I couldn't shake the idea. I would lie awake at night debating it and also whether I should have a bowl of Crispex with 10% cream (so good).

My only other option was a new crank, then new rod bolts, new lots of stuff....

So I did it. Had the Supermiata damper and timing crank sprocket broached to 7mm. Bought some keyway stock and opened up the crank. It all fits like glue after some sanding etc. I even made the keyway longer.
Just finished torqueing it all up tonight.

pics to follow.

Here are the pics

Happy endings!

Make sure to note your "bespoke" damper setup for the next owner :P

I hope to keep this car in the family forever. I've sold some things in the past I regret and this one I'll try to keep off that list.