Crankshaft Hub Bolt Loose? Torque spec?, Sigh... Options

[GregAmy]

Is it a known issue for the fan hub bolt to loosen?

Backstory: car started running like hell last Spring on my Microsquirt conversion. Wouldn't rev, #3 CHT going vertical, very hot exhaust. WTF, over? I checked some basic stuff, nothing found.

Drove it again a week later and it seemed to be getting worse. Checked the ECU logs and all seemed normal, TPS, MPS, all working as expected. I even went back to a tune that worked great in November (only difference was cold startup stuff, which I can test/adjust in the Spring when it's colder), but still even worse. Checked timing with an adjustable light at full advance, spot on for what the ignition map was calling for.

I parked the car. Life was busy this year and I just didn't have time to deal with it. But I trotted it out again in September, and it was just as bad. Since I had problems with the IGN4VW coil a year or so ago (mounted in a hot place and was cutting out), I replaced the coil with one from NAPA.

Suddenly the car would not start at all. And when I looked at the ECU logs during cranking, I was seeing 0 RPMs. Bad crank position sensor?

Today I put the car on the lift and visually inspected the crank position sensor (as well as I could, anyway; the toothed gear replaces the A/C spacer) and the spacing of the CPS tip to the teeth was clearly too large; whereas it should be about 50-thou, it was actually around 1/8"-3/16". I pried on the sensor bracket with a screwdriver, and it was solidly mounted, no looseness.

I know I spent a LOT of time getting that sensor set just right during the install (you can't get it it with the engine installed). So I knew something was up. The sensor was solidly mounted, the toothed wheel was not loose, so there was only one thing to check...

..and yup, the hub bolt was loose, allowing the hub to walk outward. Sigh...

I tightened it down - best spec I can find in the interwebs is 23ft-lbs - and of course the car fired right up and drives fine. I hope this didn't cause any other damage...

Is this common? I've never seen it before. The engine was built in California and I truly don't recall who installed the hub, them or me. It's torqued down right now and I'm going to check it on a regular basis (I thought about pulling the bolt and putting Blue Loc-Tite on it, but if I lost that bolt in there then I'd be toast and would have to pull the engine to get it back. Arthritis in the thumbs and tennis elbow so NFW I'm tempting that Fate...)

Oh, and then I broke the door cam actuator when I was putting it back in the garage..it just never ends, does it...? - GA

[930cabman]

It does not end

Having the fan/pulley loose on the crank is generally not good. Need to get things apart to get a good look at what's going on. There was thread recently with this issue.

IIRC, the hardened steel crank is no match for the aluminum hub

Good luck

[Montreal914]

Would the trigger wheel material have something with it? It is probably different than the stock spacer washer. (IMG:style_emoticons/default/confused24.gif)

Edit: Sorry, just realized you aren’t talking about the fan, but rather the hub. (IMG:style_emoticons/default/sad.gif)

[GregAmy]

I can't seem to get the idle down below 1350 RPM, no matter how far I retard the advance (that's how I'm manging the RPM).

I just rechecked the ignition timing with an adjustable timing light and it's spot-the-freak-on between the pulley timing mark and the ignition map. Which makes sense, since the toothed gear is sandwiched between the fan and its hub and the CPS is fixed.

But then I pushed the rear tin back and compared the pulley mark to the nice big "V" notch in the top of the flywheel that I painted and highlighted when I installed the engine...and the pulley mark is about three fan blades retadrded versus the flywheel mark...or about 15-20 degrees off:

http://www.914world.com/bbs2/index.php?showtopic=339759

Using the diagram in that photo ^^^ my fan pulley is right about even with blade #3 when the flywheel "V" is centered in the crankcase split line.*

Sadly, I can only conclude that the hub keyway is either destroyed or missing and the fan pulley has moved. DAMMIT.

I sincerely hope I have not damaged the crankshaft...any reasonable hopes for that?

DAMMIT.

Looks like I have a weekend project...which I hope won't turn into a winter project.

DAMMIT.

GA

*Doesn't explain why I can't reduce my idle, as that's more a symptom of too MUCH advance...but it clearly does''t match the flywheel.

[Montreal914]

Was the flywheel mark marching the fan mark when you assembled it? I remember reading that there can be discrepancies and the flywheel was a better reference (if I recall…). Hopefully the experts will chime in.

[GregAmy]

I'd love to hear otherwise, but I seem to recall that when I was installing the engine I intentionally marked the TDC on both forward and rear flanges of the fan pulley as well as the flywheel. Yellow junkyard paint marker base with a black highlight...

I'm not going to feel comfortable driving it until I pull it all apart again.

[930cabman]

I'd love to hear otherwise, but I seem to recall that when I was installing the engine I intentionally marked the TDC on both forward and rear flanges of the fan pulley as well as the flywheel. Yellow junkyard paint marker base with a black highlight...

I'm not going to feel comfortable driving it until I pull it all apart again.

Probably safe to take it down for inspection, if the fan/pulley is loose maybe it's not too bad. I would suspect the crank is not damaged, maybe the fan/pulley. Are you sure the tapered connection has come loose? The taper does all the work here, keyway is for indexing only.

[GregAmy]

Are you sure the tapered connection has come loose? The taper does all the work here, keyway is for indexing only.

No confirmation. All I did was reach in and snug the hub bolt - it had not come out entirely - down to 23 lb-ft, which seems to have seated the hub back on the taper and pulled the toothed gear back toward the CPS.

Here's the CPS design: https://thedubshop.com/type-4-crank-trigger/

But here's the question: if the hub moved rotationally on the crankshaft, then where's the keyway? I'm pretty sure the hub is fully seated back on the taper, as it's staying in place, I can visually inspect the backside behind the fan housing and the CPS is back to around 50-thou or so from the gear. I can't imagine the keyway would escape with only 1/8-3/16" walk of the hub? Wouldn't the face of the fan stop it from walking outward?

Or, did whomever put the hub on (could have been me, no idea to know for sure) totally forget to put a keyway on? I mean I suppose I could loosen the fan hub bolt and see if it spins freely...

So which is right: my fan pulley or my flywheel? Only way I can confirm TDC with any accuracy is a depth gauge in the #1 hole, and/or confirming that the fan pulley is keyed properly onto the crankshaft. To do either requires engine removal...

This is why smart people buy new cars. - GA

[cgnj]

@GregAmy
Had the same problem last spring. Woodruff key sheared. You would be the third instance that I am aware of this year.

[GregAmy]

"Woodruff key". That's the search term I needed.

And I don't like what I found.

http://www.914world.com/bbs2/index.php?showtopic=365861
http://www.914world.com/bbs2/index.php?showtopic=363970

That last one is a damned good bit of info. And if this is becoming a bit of a problem with our engines...maybe this is a problem with our rebuilds.

I'm aware that taper fits are very reliable; hell, the '00 Audi B5 S4 I used to have had every pulley on its whole V6 timing belt system secured by taper-fit pulleys and no woodruff keys! (yes that made me nervous when I was doing the t-belt job). You'd jig it all up, move things into proper place, then tighten it all down (and, I thought to myself, "and pray"...it worked).

But to be reliable, the tapers have to fit snugly; if there's any imperfections then the friction is lost...and the bolt loosens and stuff moves.

I had my 914's engine rebuilt a couple winters ago. I sent the rebuilder a core engine I bought off here, along with all my accessories, probably including the fan hub. Now, let's be clear: I don't know who assembled the fan hub on this engine. But I wonder if either of us had even considered the "sympatico" of the taper fit of the hub to the crankshaft? I know I didn't.

We're a small community. The failure of three for this whole year really makes me wonder if using valve lapping compound on these things shouldn't be a standard part of our rebuild procedures...?

I'm likely to pull the engine onto my toolbox Edd China style and lap (likely a new) hub onto my crankshaft over the winter. It's annoying, but I suspect it could be worse.

Then we can talk about that 968 I convinced myself to buy (no, not letting go of the 914s...) - GA

P.S. Dammit.

[ChrisFoley]

The front crankshaft seal rides on the fan hub. If it sustained any damage, you will have a front seal leak.
When you go in, it's probably best to ditch the old hub and install a fresh one.
Lapping the tapered face shouldn't be necessary.

[930cabman]

It does not end

Having the fan/pulley loose on the crank is generally not good. Need to get things apart to get a good look at what's going on. There was thread recently with this issue.

IIRC, the hardened steel crank is no match for the aluminum hub

Good luck

I mispoke earlier, crankshaft is hardened steel, hub IS NOT aluminum, but also steel

[Superhawk996]

But to be reliable, the tapers have to fit snugly; if there's any imperfections then the friction is lost...and the bolt loosens and stuff moves.

(IMG:style_emoticons/default/thumb3d.gif)

[GregAmy]

No front seal leaks, Chris. It only came out about 1/8" or so, so the seal was still sealin'...I agree you shouldn't need to lap it in, but I'll feel better if I do (and use Blue Loctite on the bolt).

I was thinking overnight how in the hell was the car was still running with 20 or more degrees retarded timing, let alone idling too high. Then it hit me: I'm actually off enough to where the car is running ~70 degrees or so advanced for the subsequent cylinders. And that makes sense, since I noticed it started hard the first time I tried (acted kinda like the spark plug wires were not installed correctly, which I subsequently checked) and I now do recall hearing some "tinkling" during my brief (2 miles) test drive after tightening the hub.

So it all comes down to "the hub spun on the crankshaft". I'll get a replacement hub and maybe pull the drivetrain onto my toolbox in a weekend or two (I'm fortunate to have a lift and a 44" toolbox...and beer).

Fingers crossed it just need some light filing/emery cloth and some lapping in...news to follow. - GA

[Dave97]

I had the bolt come loose on mine a year ago. It all started with replacing the alternator. I adjusted the belt, went for a test drive, made it maybe a mile heard a bunch of noise as the fan became loose. I bought the car with a 2270 motor. Pulled the engine and found not much left of the key and the crank key way on one side looked pretty bad. Now I have a stroker crank that doesn’t look good. I went for it and did the shade tree mechanic repair. I figured that it will turn out to be a total rebuild if it didn’t work anyway.
I got anther hub and new key, then lapped them. The threads in the crank were worn because the fan moved with the loose bolt. I tapped to the crank to the next size. Used jb weld to set the key into the crank. The crank had one good side of the key way. Put the hub on and lock tited the bolt. The one thing I didn’t do and should have was confirm the timing mark on the fan in relation to the engine. Just a little bit off at the hub gets bigger at the mark on the fan. It’s close as I didn’t touch the distributor before and check the timing after and it looks right.
It’s been running for a year now with about 4000 miles. No problems.
Dave

[930cabman]

I had the bolt come loose on mine a year ago. It all started with replacing the alternator. I adjusted the belt, went for a test drive, made it maybe a mile heard a bunch of noise as the fan became loose. I bought the car with a 2270 motor. Pulled the engine and found not much left of the key and the crank key way on one side looked pretty bad. Now I have a stroker crank that doesn’t look good. I went for it and did the shade tree mechanic repair. I figured that it will turn out to be a total rebuild if it didn’t work anyway.
I got anther hub and new key, then lapped them. The threads in the crank were worn because the fan moved with the loose bolt. I tapped to the crank to the next size. Used jb weld to set the key into the crank. The crank had one good side of the key way. Put the hub on and lock tited the bolt. The one thing I didn’t do and should have was confirm the timing mark on the fan in relation to the engine. Just a little bit off at the hub gets bigger at the mark on the fan. It’s close as I didn’t touch the distributor before and check the timing after and it looks right.
It’s been running for a year now with about 4000 miles. No problems.
Dave

Major victory (IMG:style_emoticons/default/piratenanner.gif) "tapped the crank" I wasn't sure this was possible with it being hardened. Must be at the journals only

My gut would have said there is little chance for lasting repair when there is damage.

[ChrisFoley]

No front seal leaks, Chris. It only came out about 1/8" or so, so the seal was still sealin'...I agree you shouldn't need to lap it in, but I'll feel better if I do (and use Blue Loctite on the bolt).

I was thinking overnight how in the hell was the car was still running with 20 or more degrees retarded timing, let alone idling too high. Then it hit me: I'm actually off enough to where the car is running ~70 degrees or so advanced for the subsequent cylinders. And that makes sense, since I noticed it started hard the first time I tried (acted kinda like the spark plug wires were not installed correctly, which I subsequently checked) and I now do recall hearing some "tinkling" during my brief (2 miles) test drive after tightening the hub.

So it all comes down to "the hub spun on the crankshaft". I'll get a replacement hub and maybe pull the drivetrain onto my toolbox in a weekend or two (I'm fortunate to have a lift and a 44" toolbox...and beer).

Fingers crossed it just need some light filing/emery cloth and some lapping in...news to follow. - GA

You can come see me for one of those hubs. I might have a good halfmoon key too.

[Montreal914]

Seems like there have been Woodruff key issues recently from what is being said…
Is this a situation of poor quality non OEM spec keys? (IMG:style_emoticons/default/confused24.gif)

Good luck with your repair. (IMG:style_emoticons/default/sad.gif)

[930cabman]

How many,what size are you looking for?

https://www.mcmaster.com/products/keys/

When fitting the hub, it should be mandatory to test with Prussian Blue

Bolt torque 23 ft/lbs

[GregAmy]

And...update. Here's several thousand words in photos.



And a nice surprise: