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

[technicalninja]

SH is right about the crank bolt not being the reason stuffs loosening up...

I got a core 2.0 from 914Sixer.
It was complete stock engine in pretty good shape.

During disassembly the crank bolt removed easily.

The crank hub not so much.

I pimp-juiced it and fitted a harmonic balancer puller.

Went tighter on that puller than I normally like too.

Long 1/2" breaker bar tight

Tapping on it with a hammer didn't do shit.

It stayed "torqued up" for a couple of days.

Impacting the flywheel bolts off (at the other end of the crank) popped that bitch right off.

The taper connection was TIGHT!

[930cabman]

SH is right about the crank bolt not being the reason stuffs loosening up...

I got a core 2.0 from 914Sixer.
It was complete stock engine in pretty good shape.

During disassembly the crank bolt removed easily.

The crank hub not so much.

I pimp-juiced it and fitted a harmonic balancer puller.

Went tighter on that puller than I normally like too.

Long 1/2" breaker bar tight

Tapping on it with a hammer didn't do shit.

It stayed "torqued up" for a couple of days.

Impacting the flywheel bolts off (at the other end of the crank) popped that bitch right off.

The taper connection was TIGHT!

If fitting correctly a tapered connection should not come apart easily. Generally a bit of heat is required to open it up a bit.

If this connection does come loose when in service, is there a telltale noise or other symptom us novices could heed? I know this winter I will be checking mine.

[GregAmy]

...is there a telltale noise or other symptom us novices could heed? I know this winter I will be checking mine.

Yes, but I suggest by then it's too late.

Either end of last driving season (October?) or beginning of this year's (April?) I began to hear a knocking noise at idle, frequency changing with the RPM, a lot like a light rod knock. It was coming from the fan end of the engine. Car drove OK, and the noise went away off-idle. I ignored it.

I suspect this was the key and keyway getting beat to s**t. If I hadn't been such an idiot I would not have ignored it.

However, it was very soon after that, like maybe 2 hours' driving time, that the engine began to run like crap and thus post #1. So I may had staved off some damage by investigating the noise sooner but I probably would have had to rework the crank anyway.

I do admit to giving the fan/hub a light tap-tap with my small ball peen hammer prior to tightening it down, both cars.

GA