https://www.miataturbo.net/superchar...thread-105612/

Hey, You
I'm about to fix this issue (in title) and I've searched through past threads and put together what I think I should do. I'd still like to go over it and see if anyone has any suggestions that differ. If you don't have any you can always post pictures of cats or tell me to go **** myself (a little harsh but I have a good sense of humor.)

A little back round on why I have to do this. I recently installed a bigger supercharger system (build thread in link up top) that uses a 2nd pulley attached to the crank pulley. I had a low rpm crank pulley wobble but it would disappear at any rpm above idle. I had this wobble with the original balancer and also after I installed a new Dorman replacement balancer. I put a breaker bar on the crank bolt, with the car in 5th, the parking brake and chalked the wheels to check that the crank bolt wasn't loose at that time. Last week the crank bolt managed to loosen itself and when I took everything apart the key had cracked at the end and also there is minor damage at the end of the keyway. Sorry for blurry picture below, apparently I was on a couple hits of that fire acid and took this photo using a potato.



I've ordered a new oem key, timing gear, boss, bolt, belt and Loctite 660. From what I've read and put together from members of this forum (who SEEM to know wtf they're talking bout) this is what I plan on doing:
1. Clean keyway with degreaser to prep for the Loctite 660.
2. Apply Loctite 660 to the end of the keyway to fill in where there is wear.
3. Place key in the slot with the chamfered end pointed towards the engine. The key should be placed as far into the keyway as it can go without the key going up on to the chamfer (level key.)
4. At this point I planned on cleaning the excess Loctite and letting it setup over night.
5. Before installing the new timing gear I was thinking about using a thin coat of anti-seize on the key and crank.
6. Install the timing gear with the old crank bolt. Will the bolt push it all the way on or will have to use a socket and tap it fully on?
7. Push crank boss on.
8. Use blue Loctite on the new crank bolt.
9. Torque to what the Haynes manual says (approx 125 ft/lbs) using the Flyin Miata crank bolt tool that bolts to the boss to keep the crank from turning.

I guess my biggest concern that I've read about is the key getting misshapen and pushed up onto the chamfer causing a false torque reading. I'm guessing the the Loctite 660 will bond the key to the crank making this not as likely but again idk. I have also read of people shaping the key to match the chamfers together but Idk if that advisable or necessary in my case.

Again any thoughts, suggestions or pictures of big booty gurls are appreciated.

Here's a video of my stupid ******* car.

 

I don't have a ton to add other than every time I've installed a lower timing gear they have slipped right on, or maaaaybe required some minor tapping. If you are driving it on with the crank bolt I'd suspect something else needs to be addressed. Or cleaned up. Rust and grime will cause it to bind but yours at least looks halfway clean through the Potato-Vision™
I've never used anti-seize for the lower gear just a quick smear of motor oil to keep corrosion in check but I doubt anti-seize would hurt. (Edit: x_25 makes a very good point about this in the next post) Unless it contaminates the Loctite, of course.

Good luck and godspeed sir. I'm interested to see if there have been any advancements in keyway repair recommendations in 2021.

 

The correct way to do this is, clean and debur everything, put 660 in keyway, put key in, slather everything else in loctite 243 (oil resistant medium strength) assemble, torque, don't touch for 24 hours.

I have always just let the clutch hold things or held the flywheel still if the engine wasy out for torquing. I have done 5 engines (including a BP4W...), not a single one has had any issues in a combined 80k miles.

You don't want antiseize anywhere near that stuff, the key is NOT what is holding things in place, in fact, it can float freely, it is there to align things. The friction from the clamp load that the bolt applies to the shoulders of the cog and boss are what holds things in place (the same way lug studs/nuts don't hold things from rotating).

 

​​​​​​I've never been happy with the results of torquing the crank bolt while in gear, especially with a sprung clutch disc. I use the "rope trick" in Cylinder #1 to block the crank and never question the efficacy of the torquing operation.

 

Loctite 243 on things besides the crank bolt?

 

Yup, anywhere metal touches metal. It helps hold things in place, but can be taken appart later with a little bit of heat if needed. It should be fine dry, but can't hurt kind of thing and is reccomended by the original loctite aplication engineer that designed the fix.

 

I just did a keyway fix the last time I rebuilt my engine. I did the requisite "De-burr everything and clean it like you were going to eat off of it" process. After letting it set while clamped in place for 24 hours the Loctite 660 was still a bit mushy. Doing some reading, I found a tech article by Loctite that said the 660 needed an anaerobic environment to set properly (I had heard nothing like that before), and that Loctite 7649 can be used to "set" the 660 if the repair was exposed to air. So I bought some 7649 (at $15 per .9oz aerosol spray bottle) and the 660 cured like I wanted it to. Been driving with that for about 1,000 miles now.

That's just my been my experience.

 

In theory, the 660 actually isn't even needed, since the key shouldn't hold anything once things are all torqued up. But I am not sure I want to guine pig on that...

 

Loctite 263 is a thread locker, while 660 is a keyway strengthening/rebuilding material (among other uses).
This user guide is good at showing where to apply the 660, page 16-18.
Loctite user guide
Loctite 660 data sheet

Loctite 660 is not recommended for more than a .010" wide gap, and cures more slowly as the gap size increases.
Since my keyway had quite a bit of slop, I used Loctite 660 along with a part of a correct thickness feeler gauge, cut to the height of the slot.
This reduced the slop down to about .002" with the feeler gauge installed. The best cleaner to use on the surfaces is isopropyl alcohol (not other types of
alcohol) or the loctite cleaner. (we use a lot of loctite adhesives at work and did significant testing, including outside lab work to arrive at this alcohol)

The user guide also shows using 660 on the shaft opposite or beside the keyway, depending on the wear on the shaft.(crank)
I only used it on the crank keyway and have not had any problems for over 4yrs.
IMO, the key is making sure the bolt is properly torqued.
Having a way of making sure the crank is locked during torqueing is essential for reliability.
Glad to hear you bought a tool.

 

So the consensus is to apply the 660, install the key, put on the gear, put on the boss, the bolt and then leave it to setup/cure?

Is the key coming coming out of place while torqueing everything down a concern? It was mentioned in a post and seemed logical.

My thought in applying the 660, installing the key and letting that setup on it's own was to avoid the 660 bonding the gear and boss to the crank.

 

Thanks to Oreo, I figured I'd post the pertinent pages from the 660 user's guide.