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Posted by: GregAmy Oct 22 2023, 11:20 AM

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

Posted by: 930cabman Oct 22 2023, 01:27 PM

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

Posted by: Montreal914 Oct 22 2023, 02:05 PM

Would the trigger wheel material have something with it? It is probably different than the stock spacer washer.

Edit: Sorry, just realized you aren’t talking about the fan, but rather the hub.

Posted by: GregAmy Oct 22 2023, 03:50 PM

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.

Posted by: Montreal914 Oct 22 2023, 04:41 PM

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.

Posted by: GregAmy Oct 22 2023, 05:11 PM

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.

Posted by: 930cabman Oct 22 2023, 05:49 PM

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.

Posted by: GregAmy Oct 22 2023, 06:22 PM

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

Posted by: cgnj Oct 22 2023, 06:33 PM

@http://www.914world.com/bbs2/index.php?showuser=15565
Had the same problem last spring. Woodruff key sheared. You would be the third instance that I am aware of this year.

Posted by: GregAmy Oct 22 2023, 07:52 PM

"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.

Posted by: ChrisFoley Oct 23 2023, 04:47 AM

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.

Posted by: 930cabman Oct 23 2023, 05:03 AM

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

Posted by: Superhawk996 Oct 23 2023, 08:07 AM

Posted by: GregAmy Oct 23 2023, 08:47 AM

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

Posted by: Dave97 Oct 23 2023, 09:06 AM

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

Posted by: 930cabman Oct 23 2023, 10:49 AM

Major victory "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.

Posted by: ChrisFoley Oct 23 2023, 12:50 PM

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

Posted by: Montreal914 Oct 23 2023, 01:58 PM

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?

Good luck with your repair.

Posted by: 930cabman Oct 24 2023, 01:32 PM

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

Posted by: GregAmy Oct 30 2023, 01:00 PM

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



And a nice surprise:

Posted by: 930cabman Oct 30 2023, 01:07 PM

Ouch

Any idea how long this had been loose?

Think this item will go on my list of winter projects, check and double check the taper fit

Posted by: GregAmy Oct 30 2023, 01:36 PM

Just a wild-assed guess, but "not long at all". My fuel logs indicate I've driven it only about 400 miles since October 2021 (not a typo)...

The engine was rebuilt in November 2020 by a company out west, and I installed it over that winter. Fuel logs indicate that was roughly 2,000 miles ago. Most of the miles I put on it since were in 2021.

I seem to recall hearing a light banging noise from the front of the engine earlier this year or maybe late last year, but it went away off idle. Since I had installed a crank position sensor toothed gear behind the fan pulley when I installed the rebuilt engine I thought ok maybe I didn't tighten the fan? So I actually stuck a socket in there to check those bolts but they were fine...but I didn't think to check the hub bolt since I had not removed it since the engine rebuild; there was no reason to.

How long was the bolt loose? Anyone's guess. But with two o-rings stuck in there, maybe it wasn't even tight when I got the engine (or maybe the crushed o-rings affected the torque). I don't recall if I ever checked it.

I'd suggest it was a major failure of imagination on my part for continuing to drive the car once I heard that light knocking happening, and I should have parked the car right then and there to investigate it. That's my fault.

I'd also have to offer that, absent the cranked tooth gear getting massively off time causing the engine to basically stop running, it's quite possible I'd still be driving it anyway.

What a mess. We'll see if we can repair it. Otherwise I think the car will have to get stored somewhere long-term, as I recently got laid off and I have no desire, money, or patience to pay for a replacement crankshaft and new engine rebuild.

We'll see what happens. Fingers crossed. - GA

Posted by: AZBanks Oct 30 2023, 01:49 PM

This happened to me.
The guy who put the engine back together got distracted and didn't tighten the crank bolt properly. It was just finger tight when the whole engine went back in the car.
It worked loose and sheared the woodruff key just like the previous pictures.
I noticed it at the emissions testing station. I was watching as the engine was running but the fan was not turning. It got hot enough to deform the rubber grommets around the spark plug wires.

The next time I saw the guy, I told him he was an idiot and tried to kick his @$$.











My wife is not happy about the broken mirror.

Posted by: GregAmy Oct 30 2023, 01:58 PM

You owe my a keyboard.

Posted by: Superhawk996 Oct 30 2023, 02:21 PM

Pretty good chance you can repair it with careful file work, emery cloth, lapping and Prussian Blue.

Patience

I’ve repaired worse looking Morse tapers to useable condition with just those basic items.


Don’t lose hope. Sorry to hear about the layoff - that hurts. Why do those companies always pull this around the holidays. them!

Posted by: ChrisFoley Oct 30 2023, 06:07 PM

I'm a bit more worried about the damaged keygroove. Considering how to reshape the groove after doing some weld buildup on the edge... or possibly using bronze to secure the key on the crank. I'm pondering if I can do it on the assembled longblock. Tough spot to work in. First step will be to practice on another crank, without all the challenges.

Posted by: 930cabman Oct 30 2023, 06:22 PM

This is not an easy repair. It's possible you can pull it off, but .....

From what I know the key/keyway do little work other than indexing the hub. At least 90% of the work is done with a well fitting tight tapered connection.

Posted by: Superhawk996 Oct 30 2023, 06:40 PM

Woodruff key only determines timing mark location relative to crank.

If the key is a little loose side to side it will only affect timing as seen with a timing light. Example 27 degrees may now be 25. A little trial and error will figure out the offset.

The key has no significant effect upon securing the fan to the crank once the taper is engaged properly. This is borne out by how easily the key shears once the taper comes loose and can no longer handle the torque.

Posted by: Superhawk996 Oct 30 2023, 06:45 PM

The taper does 100% of the work.

Machine tools like Jacob’s tapers, and Morse tapers, ER collets; all can take a lot of torque and none of them have a key way or positive engagement feature to resist torque. R8 taper has a key way, but that is only to prevent the collet from rotating while the draw bar is tightened, pulling the collet tight into the R8 taper.

Posted by: GregAmy Oct 31 2023, 07:05 AM

I was recently reminded that early Miatas had a problem with the valve drive gear bolt coming loose; we used to lose Miata crankshafts often in racing, and checking the crankshaft bolt became a regular pre-weekend prep item. The design was fixed after '91 with a longer nose and bigger bolt.

The Miata design is different, in that it's a straight fit and the keyway drives the pulley. But a buddy reminded me of the DIY trick for "repairing" the situation if you're on a budget.

https://www.miata.net/garage/hsue/Loctite%20Crank%20Fix%20-%20Part%201.htm

And a video from Loctite: https://www.youtube.com/watch?v=LLSLtr0ECbc&ab_channel=LOCTITE%C2%AENorthAmerica

I'm leaning toward small files to knock down the high bits on the backside of the key damage and then valve-lapping-compound the taper all the way around with a replacement hub (and bolt and key). Chris is leaning toward having me schlep the assembly to his shop for bronze TIG, but I'm wondering, given a good taper, if something as simple as Loctite 660 to stabilize the key would be fine. Loctite lists the shear strength of 660 as approaching 3000 psi, which is more than adequate. What I can't tell if the keyway would removable; I'm guessing not.

Let's check those bolts, team. It's not hard at all to do and I fear there may be more of us out there...23 ft-lbs and use Loctite 243 on the bolt. - GA

Posted by: Superhawk996 Oct 31 2023, 08:18 AM

Loctite site says 500F heat to remove the key.

I have no experience with that product but sure looks interesting and appropriate for the application. I would imagine you’ll still get minor variation in timing depending on how perpendicular the key is to the crank.

I remember the Miata fiasco vividly - had a friend with a 90’. Mine was a 91’ specifically to avoid that issue. Pretty rare for the Japanese to screw up the engineering that badly but it happened - probably in the rush to get it to market. Put 220k miles on my 91 and never had an issue after they fixed it. Completely different design than a taper though!

https://www.youtube.com/watch?v=6-m2IT4Xojo

Posted by: GregAmy Oct 31 2023, 08:34 AM

What grit lapping compound do we suggest?

Amazon cart has:
- Loctite 660 "quick metal"
- Loctite 22355 cleaner/degreaser
- Loctite 7649 primer
- Loctite 243 Blue threadlocker
- Small set of needle diamond jeweler's files

Add in some lapping compound and I can probably get this done for less than $120 and an hour or so of patient work (plus reinstall)...we'll see. - GA

P.S., I'm not worried about small timing variations. I can set my baseline timing off the mark I put on the flywheel, visible by moving the rear sheet metal back. I can even adjust it in the Microsquirt so that the pulley matches. The important part is ensuring the hub is secure and never to move again...

Posted by: Superhawk996 Oct 31 2023, 10:03 AM

Start coarse and work down - use Prussian blue to monitor progress until you have uniform contact around - across the entire taper . With lapping compound it’s not like you’ll ever take too much material off.

Pits below the surface are of zero concern but you don’t want any high spots.

Posted by: Superhawk996 Oct 31 2023, 10:12 AM

Budget three hours

Anytime I tell my wife it will only take an hour in the garage - it’s three or four.

Per other thread, Clay’s suggestion to pack the seal pocket with grease and/or magnet to catch shavings should be a good one.

Posted by: 930cabman Oct 31 2023, 12:58 PM

Knock down the high spots, the low spots will be 0 contact, but will not hurt you

The high spots create point loads and will in a short time start to rock. You are looking for as close to 100% contact as you can get. The Prussian Blue will tell that story

Posted by: GregAmy Nov 3 2023, 08:11 AM

Is this a build blog now...? Hey, maybe it'll help someone else in the future.

More conversation-via-photos, as follows:

- Reminder of the original discovery
- First pass at finding the high spots (using the sharpie method)
-

Posted by: GregAmy Nov 3 2023, 08:20 AM

Is this a build blog now...? Hey, maybe it'll help someone else in the future.

More conversation-via-photos, as follows:

- Reminder of the original discovery
- First pass at finding the high spots (using the sharpie method)
- Surprisingly little rework with small jeweler's files and then a couple passes with 150 grit lapping compound
- Couple more 150 grit passes and the nose came in
- Couple passes with 280 grit lapping compound. Not much difference so I'm going with this
- Nighty-nite for the Loctite 660 to cure overnight

Wake up this AM expecting it to all be good...and the Loctite 660 hasn't set. I was listed as anerobic and for spaces up to 20-thou (my gap is about 1.5mm) so maybe I shouldn't be so disappointed. I sent a note to Loctite for guidance.

Maybe steel-infused JBWeld is the answer...? <shudder>

More soon. - GA

Posted by: Porschef Nov 3 2023, 08:35 AM

That looks pretty good Greg

Tedious work, no doubt.

I know lots of folks swear by JB Weld but has anyone tried Marine Tex? It’s pretty tough stuff that’s also workable, on the package it says can be used to repair manifolds, etc...

Posted by: GregAmy Nov 3 2023, 08:44 AM

Surprisingly, easier than expected. Really, only an hour or so worth of work (with another hour tossed in for being careful).

I'm all ears for any alternative materials; Loctite's response was, "It could be likely that your product is counterfeit as we do not support Industrial products sold though Amazon. Or you could not be using the product correctly, a primer is needed if the product is used on a passive metal."

GA

Posted by: 930cabman Nov 3 2023, 09:07 AM

Looks like you are getting a decent amount of contact. What did you use as an abrasive?

Posted by: Superhawk996 Nov 3 2023, 11:12 AM

Definitely looking better and promising.

Would love to see that lapped down to 400 or finer.

The smoother the surface finish, the higher the torque that can be applied to the taper.

I wonder if the loctite would have cured more readily with clamp force applied to the key to ensure that no oxygen was able to get in under the key or on the sides to get the cure started? Assume you did use primer too? Their response to the question is highly annoying as if Amazon is the only place that could end up with counterfeit product and that seems unlikely to begin with. Who’s getting rich counterfitting such a specialized product?

Not like your average auto parts store or Walmart carries their more specialized Loctite products!

Posted by: rudedude Nov 3 2023, 11:46 AM

You might want to make sure that the hub doesn’t bottom on the crank face before the taper is fully engaged. Could the crank have been to long and kept the first hub from fully engaging? Other people have had issues with counterfeit products from amazon sealing 911 cases.

Posted by: ClayPerrine Nov 3 2023, 02:13 PM

This same thing happened to Betty's car 35 years ago in a little town called Copperas Cove, Texas. We were in town for an AX, and on her last, best run, the engine spit the fan into the shroud. She always said it was because of the lightened load on the engine gave her more HP to the wheels!

Turns out the bolt holding the hub onto the crank broke. So, with the help of a local auto parts shop owner, I got a wodruff key and a new washer and bolt, plus some locktite. I then took the hub off the fan, and put it back together. No crank polishing, no checking it, nothing. We had to drive home that day to be at work the next day. So It was a "field expedient" repair. One of the "repair" techniques I did was to use a brass hammer to drive the hub onto the crank before installing the bolt. That way I wasn't pulling against the bolt to install the hub.

The damn thing stayed on the engine for another 5 years before I had to remove it to replace the seal. And it was a bitch to get back off when I did.


Good luck in your fix!

Posted by: GregAmy Nov 4 2023, 07:36 AM

Still ongoing. Using a dental pick I realized the very bottom part was solid (it's anaerobic, after all) and the key was supported so I put in the o-ring and crank seal for final install. Then as I was taking it out one last time for inspection (Shroedinger's o-ring) the key came out with it, along with some of the upper part of the 660.

Visual inspection showed that the bottom part of the 660 was still there and when I put the key back in it was well-supported, no movement. I slipped the hub on and there was no more side-to-side movement. So I packed the top of the space with "JBWeld Steel" and I'm going with that. It'll be reassembled today.

New spark plugs, fresh valve adjustment (love me them zero-lash chromoly pushrods) and I'll get the whole thing leisurely installed this week/end.

Loctive Clover 150 grit lapping compound, then a follow up with 280 grit lapping compound. Got plenty left if you need some...


Thought about going higher than 280 but honestly I think this will be fine. I guess we'll see.

Did not use the primer as I couldn't get it within a reasonable timeframe.


It's not; you can see how far up the lapping compound was grinding on the taper and there's a lot of space left. And when I test-fit the hub with the bolt torqued down the or-ring wasn't over-compressed.

I do kinda wish that I had measured the distance from the end of the hub to the nose of the crankshaft; I'm curious how much farther in all this cleanup and grinding allowed...

Posted by: Superhawk996 Nov 4 2023, 07:54 AM

Will be watching.

I think it’s all going to work out just fine.

Posted by: 930cabman Nov 4 2023, 11:22 AM

maybe put a bit of clay to get a measure from the back of the hub to the face of the crank? It's hard to imagine you took off too much material, but a double check might not be a bad idea.

Posted by: Superhawk996 Nov 4 2023, 12:45 PM

NOTE: not an attack on anyone - no ill intent. I understand why folks would be concerned.

The distance the taper moves inward will be a fraction of few thousandths of an inch.

The distance moved inward is a function of how much material was removed (lets call that A) and the angle of the taper (lets call that angle Z).

The depth moved inward will be A x sine(Z).

Lets assume some numbers. Let's say .001" of material was removed off the surface of the taper by lapping. This would be quite a lot.

Let's assume the taper angle is 15 degrees (I honestly don't know what it is but it could be measured).

So removing .001" of material off the face of a 15 degree taper moves it inward .001" x sine(15) = .00026". You couldn't conceivably measure that with out CNC measuring devices.


Sleep easy tonight.

Posted by: GregAmy Nov 4 2023, 03:39 PM

It's done, no more checks/changes. Hub, toothed gear, fan, and housing are on and torqued, valves getting adjusted tomorrow and back into the car it goes.

I'm sincerely hoping that I never have to post in this thread for as long as I own this car.

Go check your fan hub torque. - GA

Posted by: GregAmy Nov 7 2023, 06:20 PM

Ok, really really last post here, I'm hoping: drivetrain installed, engine is running nice. Took it for a spin tonight and I'm pleased.

Interesting data point, the difference between the notch on the flywheel and the zero mark on the front pulley are 5 degrees apart, per my adjustable timing light; I don't know if it was like that before, as I always used the pully. I'll use the flywheel mark as my core reference. - GA

Posted by: GregAmy Nov 13 2023, 07:47 AM

Ok, seems I can't quit you...

I was cleaning up the garage yesterday from the mess I made with this project. Came across the old pulley hub (with its slice of key still in the groove) and decided to add it to my "wall of shame" of failed parts I have (when you get into racing you tend to collect stuff like this).

On the shelf, I picked up the broken crankshaft from 2019(?) and was going to slide the hub on there but the crank still had a key in it; I tapped the key out and noted that the key was damaged, offset like the old offset keys we used to use on VW overhead cams for timing. And there were scuff marks on the downstream side of the crank nose where its pulley was chattering.

So that engine's pulley was loose, too. I don't know if that was related to the crankshaft failure, but this certainly caught my attention.

I put the race car on the lift and checked its crank bolt - that engine uses a Bus fan and shroud - and that bolt, too, was slightly loose, about 1/16 of a turn to get it to 23 ft-lbs. So I removed the bolt, loctite blue'd it, and reinstalled to 30 ft-lbs. And I know who built that engine and I know he would not have missed something like this.

One time is random; twice is coincidental; three times is a trend. I think we have a trend going on here. I certainly seem to...

Does anyone know the class of bolt that's being used here? The markings on it are not standard. If it's equivalent to a 10.9 then most charts are showing in the 40 ft-lbs range. The underside of the bolt has locks similar to a Schnorr washer, and I'm sure the engineer didn't want that taper to get hammered in too tight (it would be a bitch to get loose).

However, I noticed all three crank washers have a circular groove where those locks have dug in; if that groove is too deep then the locks may be making less grip contact. Are these supposed to be single-use bolts and washers?

Maybe I'm overthinking this thing, but I've now experienced three potential failures, just in my own garage. So I'm'a thinking that proper torque, Loctite Blue, and maybe new bolts and washers is in order here. And maybe a higher torque value.

Has anyone else checked theirs? What have you found? - GA




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Posted by: Superhawk996 Nov 13 2023, 10:37 AM

I think you’re missing the principle of how a taper works.

It MUST be tight fitting. It should be so tight that it requires a pulley puller, some heat, and a few brass hammer bangs to remove the hub after it has been installed.

Posted by: Superhawk996 Nov 13 2023, 10:50 AM

This

Though I generally don’t want to be hammering / impacting main bearings you get the point.

It should be a a bear to remove it after a proper install with well matched tapers.



After the install, the bolt is doing very little to hold the joint together.

Posted by: technicalninja Nov 13 2023, 11:32 AM

That key looks like a specially designed offset key, not a damaged stocker.
That's weird!
Normally special keys like that are used to offset cam timing and not offset the hub alone...

For the reason why all of your crank hardware appears to loosen over time.

This is a bit of a guess on my part but it's worth thinking about.

The Type 4 engine has no vibration damper on it.

In its stock form it probably works fine without a damper.

Each power stroke applies individual power "spikes" into the crank. As these spikes increase in intensity and cycle rate this hammering can induce resonance into the crank assembly.

Making the rotating mass heavier reduces this tendency. All of the dual mass flywheel that are in use today are stupid heavy.

Slowing the rotating mass down helps combat this as well but that's not "sports car".

Adding some type of elastomer in an external pully is how these issues have been delt with in the past by most manufactures.

A complete BS "power upgrade" for many cars is a solid crank hub and lightweight smaller diameter drive pully. Sometimes these were listed as a "power pully."

What you get with one of the puppies is accessories that don't work worth a shit at idle and excessive crankshaft resonance.
You end up with broken locating keys, torn up crankshafts, loose crank bolts, and crank driven oil pump explosions (this is very common!!!).

I REMOVE "power pullies" whenever I find one...
A stock balancer is vastly superior to one of these.
For street cars I try to use a "Fluid Damper" if it's available for that engine.
Fluid Damper is awesome at eliminating harmonics and resonance below 6500-7500 rpm.
For an engine constantly operating at or above those numbers I prefer a tunable elastomer balancer (you can get different O-rings for these) or a specific balancer for high rpm use. It will be listed as a "tuned" balancer and it should spec out an RPM range where it is effective.

The T4 has no harmonic balancer anyway.

Most performance oriented T4s are using much lighter pistons and rods and being spun to higher engine speeds.
It looks like most decently built T4 have at least 50% more power than stock and some double the stock power levels.

I agree with Jeff.

I'll be spending extra time on the crank snout and pully interface.
30lbs sounds good too.
New hardware (maybe upgraded) should be incorporated.
Medically clean threads and blue Loctite will be used.
Once a year inspections (maybe more often?) will be done.

My thoughts...
Maybe wrong?

And now SuperHawk will produce a white paper showing something else...

Posted by: technicalninja Nov 13 2023, 12:08 PM

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!

Posted by: Superhawk996 Nov 13 2023, 12:19 PM

Horizontally opposed engine has nearly perfectly balanced 1st and 2nd order harmonics. Therefore doesn’t need or get a harmonic balancer.

And that my friend is why I love air cooled horizontally opposed engines. Simple, light, and smooth running vs inline 4, V6, and V8. I would die for a V12 but fortunately Tygaboy hasn’t fit one in a 914 . . . Yet.

Posted by: 930cabman Nov 13 2023, 12:23 PM

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.

Posted by: technicalninja Nov 13 2023, 12:40 PM

OK Master...

Why are SO many high-performance balancers available for the Subaru 4 cylinders?

There's a bunch of different Fluid dampers for them as well.

I cannot remember a Subie with a solid balancer as stock equipment ever.
I've been repairing Subies since the early 80s.
Seen WAY TOO MANY.



I didn't say I was right...

I'm trying to help determine why one member (a freaking knowledgeable one!) has 3 of the same problem.

I'm in agreement with Jeff.

3 is NOT a fluke.

SH, what do you think is the reason for Jeff seeing as many of these as he has?

Posted by: 930cabman Nov 13 2023, 12:45 PM

I will put my $5. on they were never properly fit, checked for a high percentage of contact and torqued correctly.

Posted by: GregAmy Nov 13 2023, 02:41 PM

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

Posted by: Geezer914 Nov 13 2023, 04:22 PM

Greg, sorry to hear about the layoff. After reading all the posts, I think I am going to remove the fan hub bolt, loc tight it and re-torq it for peace of mind.

Posted by: Superhawk996 Nov 13 2023, 07:13 PM

I’m no expert expert on Subaru’s for sure but I’ll give you my speculation and what came up with after reading a couple of Subaru SAE papers.


Subaru does indeed call it a harmonic balancer but they don’t say what frequency they are tuning it for. I did find a waterfall plot of their 1st order and 2nd order frequencies and indeed they are much lower than typical 2nd order harmonics from an inline 4 cylinder as would be expected. There does seem the be a weird set of vibrations at 1.5 engine order.



This leads to two points of speculation as to why they have it.

1) It is likely tuned for other engine NVH harmonics coming from A/C, power steering, or something else that would be objectionable to customers? A/C would be the prime suspect since all compressors impart objectionable vibrations on the engine especially at idle. Could these be the 1.5x engine order vibrations that show up in their NVH waterfall plot?

2) the Subaru crankshaft is longer than a VW T4 crank. The Subi is a 5 bearing crank vs the T4 which is effectively a 3 bearing crank (4th nose bearing doesn’t support much). The T4 crank has much thicker webs between journals and it may be a stiffer crank.

So the Subi may have some crankshaft torsional vibration issues as you were alluding to. They also spin the crank to higher RPMs than the T4 and forces go up as the square of crank RPM. Maybe they are using the harmonic damper to damp crankshaft torsional vibrations that the T4 isn’t subject to.

I know VW and Porsche air cooled engines far better than Subaru’s and the only thing I can say is that none of the VW air cooled engines nor the early Porsche 6 cylinders used a harmonic balancer. And the Porsche six cylinder crank is easily as long or longer than a Subi four cylinder. Porsche six’s were similar or higher power output per liter than Subi (naturally aspirated) so it seems odd to me that they would need the harmonic balancer due to crankshaft torsional vibrations related to durability, but the devil is in the details and I certainly don’t have all the details on Subi’s. Perhaps the Subi crank is not as stiff as the Porsche six or VW T4?

@http://www.914world.com/bbs2/index.php?showuser=27135

As you elegantly stated . . . I may not be right. I’m always open to be schooled and I’ll keep digging to see if I can better understand why Subaru is using a harmonic damper and what frequency they have it tuned for.

Posted by: Superhawk996 Nov 13 2023, 07:15 PM

Posted by: Superhawk996 Nov 13 2023, 07:16 PM

duplicate

Posted by: technicalninja Nov 13 2023, 11:09 PM

You BEASTS!

Just throw Greg under the bus will ya!

Greg, always remember, I'll have your back!

The hawk and the cabman are subversive...

Now for serious:

SH- I'd be a pissed off engineer if the NVH resonance graphs were taken with ANY accessories running at all.

Subaru has almost exclusively used either vane style compressors (exactly like a mechanical air pump-just sealed up better) or scroll style compressors.
Both designs do not have reciprocating pistons and are super smooth in operation.

I may use a small scroll for a retrofit in a 914 mainly for the smoothness and lack of cycle torque change. If you are forced to use a cycling compressor the scroll design (which is supposed to be the most efficient) has almost zero engagement torque.
It's damn hard to tell when it engages. Often no idle compensation is needed.
I've kept 3 baby Subie scrolls (dead ones) as test fitters.

Subie compressors are probably not a source of serious NVH noise...

I do have a question. You mentioned EARLY 911 motors did not have harmonic balancers. Does this mean later ones do?
If so, when did they arrive?
What other changes occurred along with the balancer?

Balancer is really not what this device should be called.
Vibration shunt or eliminator sounds better in my book.


Ya'll be easy on Greg now...

Posted by: Superhawk996 Nov 14 2023, 12:05 AM

Not trying to throw anyone under the bus so to speak.

Checking torque after the fact with a typical clicker wrench isn’t necessarily an indication that the hub is loose or that it wasn’t torqued properly on assembly. I fully believe that the race car engine in particular was built properly.

I don’t want to go into a deep dive on how fastener toque specs and subsequent audit torque checks are established but it will suffice to say that we would need way more than a sample size of two or three fasteners.

Likewise simply jacking up the torque may or may not help. If the fastener torque spec is close to yield, increasing it arbitrarily can take it over yield and there will certainly be some loss of clamp load if the fastener wasn’t designed for a torque to yield application. I don’t think that is the case here but I don’t have the fastener data to know one way or the other since I don’t know what grade the hub fastener was as OEM or if someone swapped it out for something lesser along the way (doubt it).

At this point I’m deep in the weeds and simply hoping that the fix holds up for the long haul.

Posted by: Superhawk996 Nov 14 2023, 12:21 AM

Not sure when later engines got a harmonic damper and/or which variants get it. Modern build complexity is beyond belief. What engine variant, PDK vs manual, dual mass flywheels vs single mass light weight flywheels, 993, 996, 997, etc. Late model 911 stuff isn’t my thing.

The proper engineering term is tuned mass damper.

@http://www.914world.com/bbs2/index.php?showuser=27135

Posted by: technicalninja Nov 14 2023, 12:34 AM

Greg, when I first saw the damage on the crank snout, I thought it was trashed and un-usable.

Your repair appears to be excellent!

I thought "WOW did that clean up nice!" and I'd expect what you massaged to work fine for years.

Really nice repair work there IMO...


I'm surprised that no-one has mentioned a sleeve retaining liquid.

I've used this on non-tapered crank snouts to hold on loose crank gears when the crank should have been replaced. This is a "Hail Mary", last ditch, southern engineering fix...

https://www.amazon.com/Retaining-Compound-Cylindrical-Components-Assemblies/dp/B09VH9VJT6/ref=asc_df_B09VHBQ8W3/?tag=hyprod-20&linkCode=df0&hvadid=602805991085&hvpos=&hvnetw=g&hvrand=8084208597450635581&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9027220&hvtargid=pla-1666653096406&th=1

I've never had a "glued" together assembly come apart, but I wouldn't warranty that for 10 minutes.

You might not be able to get a tapered joint to separate after using this stuff.
Fire would probably be a requirement.

Posted by: Superhawk996 Nov 16 2023, 07:10 PM

@http://www.914world.com/bbs2/index.php?showuser=27135

Found some interesting data for the FA engine



Harmonic damper is tuned for 2nd order - for about a 150hz resonance.

I’ve overlaid in red what the crankshaft resonance would probably look like without a damper.

When a tuned mass damper (harmonic damper) is used it cannot reduce the energy input; it can only redistribute the energy to other frequencies. When it does this it usually creates two side bands - one above and one below the resonant peak. I’ve artfully illustrated this in green.

These plots appear to have been created from data supplied by Fluiddampr so there is the comparison of OEM Harmonic Damper to their product.

While you can see they (Fluiddampr) knock the resonance down further, they do this by pushing the energy out to higher frequency (RPM) range. This would not be a good thing for extended racing / track day use where the engine would spend more time at those higher RPMs.

The bottom line: FA motor making a whole lot more HP and Torque than our measly T4s and it would appear that perhaps the Subaru cranks has some propensity for a 150Hz resonance.

Another interesting dilemma is that just because it has this resonant frequency doesn’t mean that it is a durability issue. It just may be that Subaru is using the damper to calm NVH and make the car more enjoyable to drive. Without access to Subaru durability or warranty data we can’t know for sure which reason it is that Subaru is using the harmonic damper.

Obviously, we would need similar data for the VW T4 to draw any conclusions about whether the T4 would benefit from a harmonic damper and of course that data would be needed to tune it appropriately.

Source:
https://www.ft86club.com/forums/showthread.php?t=139127


PS: Thanks to you I’ve learned a little more about subi’s than I knew a few days ago

Posted by: technicalninja Nov 16 2023, 07:26 PM

Once again, your tenacity is impressive!

Thanks for the time you spent researching this.

I need to think up some un-answerable question for you...

Posted by: Superhawk996 Nov 16 2023, 07:54 PM

@http://www.914world.com/bbs2/index.php?showuser=27135



Also keep in mind, that the 2nd order harmonics of the boxer engine are already quite low as compared to an in-line 4 per the data in post #61. The more I think about that, the more likely it is that Subaru is using the harmonic damper for NVH reasons but we’ll never know since I don’t know anyone that works for Subaru to get any insight.

Posted by: technicalninja Nov 17 2023, 09:50 AM

@http://www.914world.com/bbs2/index.php?showuser=22428

I didn't intend to insinuate that you were wrong.

I was referring to me!

You are an absolutely top-notch source for knowledge.

You will go through the trouble of looking stuff up like no-one else I know.

I really appreciate your input.



On the loosening up of the crank bolt BS.

In 40 years of building stuff (very limited VW and Porsche) I've found as you improve horsepower you commonly need more vibration attenuation than less.

In the Miata world the stock balancer is SO bad many tuners want an aftermarket balancer BEFORE a tuning session. The stock balancer is not good enough for double or triple the horsepower.
Now, I'm tripling power on these, most of the T4 work on here doesn't triple the power so the need for increased balancing will be less.

I've seen multiple threads in the short time I've been on here regarding crank noses being damaged. Many of these could be from improper mounting but there are enough of them that makes me think "maybe there's more to this than we realize".

I like my street-based vehicles to have excessive damping.
I'm also a believer in full weight flywheels to increase transmission life...

Thanks again for a scientific look at the balancing requirements for an H layout engine.
It has been informative!

Posted by: 930cabman Nov 17 2023, 10:48 AM

Good luck with that, Mr SH is most often right on target and we should all be thankful for his input.

Posted by: Superhawk996 Nov 17 2023, 12:52 PM

I think part of that is just due to your short time on the site.

Like you - I’m new too, having only been here since late 2018.

There have been two instances of crank nose loosening that got a lot of traffic in the last 9 months or so which makes it seem like it occurring often. But honestly, I don’t think I’ve seen more than 3 or four instances since 2019. Have there been more? Certainly. But, probably not a regular occurrence by any stretch of the imagination.

Like so many things, it’s partly an issue of people not understanding how things are designed to work.

What do I mean by that?

In the case of a taper, people simply think tightening the joint to spec is good enough. But that is 100% contingent on having a taper that is clean, dry, and has good interference fit between the two parts as they would have been when fresh back in 1970s when taken out of the dunnage for the engines initial build.

I think as parts get older and more beat up, we will see this issue more often. Especially with the home built engines where good intentions may not be enough to make up for a lack of attention to detail (not aimed at anyone in particular - especially OP).

For some reason, lots of people don’t have a real appreciation for how precise fits in an engine are. Likewise many don’t have an appreciation for how easily steel can be damaged.

I’ve worked in engine plants and I can tell you horror stories - mostly related to new hires that don’t have an appreciation for the precision machining that parts have and how they need to be protected from damage. There is a lot of work and training done to impart knowledge of how important it is to handle parts with care, yet you still see instances where someone isn’t thinking and damage can happen.

To some extent we all have to fight the urge to just get a job done and we need to focus on doing it right. I know I’m guilty of this sometimes.

Anyway, just a point of view for consideration about how common this issue may or may not be.

Posted by: Superhawk996 Nov 17 2023, 01:05 PM

Here’s the thing. The Miata harmonic damper is PERFECTLY adequate for a stock engine - which is what Mazda designed it for.

It’s not fair to say the damper is inadequate for an engine that has been modified for 2x or 3x the horsepower. Many things in the engine are going to be inadequate at that point.

I had a stock 91’ Miata that was regularly autocrossed and ran weekend track days. That Miata went to 228k before I finally had to let it go due to rust that was getting too dicey. No issues what so ever with the stock harmonic damper or engine durability. I gave it away with the engine still running strongly.

The video below is from my car - used to collect a bet for a case of beer that the engine wouldn’t last to 100k without a rebuild the way I was driving it. I easily won the 100k bet at which point he wanted to go 200k - double or nothing.

The beer was great


https://www.youtube.com/watch?v=6-m2IT4Xojo?si=jJjnsojGL3tlJ9w9

Posted by: Superhawk996 Nov 17 2023, 01:16 PM

No offense taken at all nor did I think that was what you implied. I certainly don’t mind being called out when i am wrong. That’s how we learn new things !

@http://www.914world.com/bbs2/index.php?showuser=27135

Posted by: technicalninja Nov 17 2023, 01:18 PM

In stock form I'd have bet 250K...

Bet your engine is NOT what took the 91 down and 91s still had the short nose crank from the original 323 motor.

I had one of the earliest 323s with a crankshaft failure.

I wrote the "service procedure" for Mazda as they had "remove engine from car" as the first step and if it's an automatic you could change a crank in-chassis with a couple of LONG bolts to push the auto trans back far enough to clear the flexplate.
You don't disconnect anything!

Shaved over 4 hours off of the job...


Mazda blew the doors off of all the previous iterations of the small 2 place roadsters that came before it.

The only one that was close was the Fiat Spider and the Miata body-slammed that...

It was the first RELAIBLE sports car IMO.

Posted by: GregAmy Nov 21 2023, 11:08 AM

I was having a dinner conversation with a couple buddies last night about this problem, how the tapers came loose and damaged the crankshaft.

One buddy - a Chevy LS guy - started making fun of old Germans with wonky engineering ideas and why didn't they just do like 'Merica and put a press fit and key there.

The other buddy drives a late-model BMW E-something (M4? I don't know those cars) just a few years old. He noted that the BMW line is still using that taper fit for driving the cam belts, without a keyway, and is having problem with guys modding their engines to the point where when suddenly downshifting the crank hubs are spinning and destroying multi-$10Kengines. The aftermarket "fix" is apparently to drill the crankshaft for a pin/key to stop that.

And that got my brain to remembering when I did my camshafts belt on my '00 Audi S4 at 100k miles, some 14 years ago. I remember that job with dread. The cam pulleys were taper-fit only, no drive keys. You'd set the engine to TDC and remove the tensioners and the belt, then loosen the bolts holding on the gears; you'd put the new belt and idler pulleys on and then setup this elaborate (rented) alignment tool with bars and pins that would locate all the engine drive components - crankshaft, camshafts, whatever was in there - at a specific rotation. And then you'd tighten the pulleys down to spec.

I remember thinking at the time that my entire investment in that car was wholly dependent on a bunch of taper-fit pulleys being properly secured by bolts...and if anything slipped I'd be funked...but nothing ever did.

Amazing how thoughts like that get buried away in your head, only to be exhumed at interesting times...

So ze Germans are still onboard with this taper fit thing even today. - GA

Posted by: 930cabman Nov 21 2023, 02:28 PM

Exactly why myself and many more just love the simplicity of our 1/2+ century old sporting machines.

Posted by: technicalninja Nov 21 2023, 09:37 PM

The later model Audi with the direct injected V6 changed to chains!

They moved them to the back of the engine, and should you need to do anything you get to remove the FREAKING transaxle!
The tensioners and rails are a source of problems with this motor.
Poor oil change intervals dooms these to an early demise.

Sometimes newer is not necessarily better...