Damaged crankshaft keyway slot, any suggestions?

[Benski]

My fault. I installed a complete timing belt kit about 20k miles ago. I did my best to immobilize the crankshaft pulley/hb while tightening the crankshaft bolt. Well I didn't get near enough torque on it. Now after getting A REAL MECHANIC to get the hb off with a torch, I got problems. I need to replace the hb, gear and damaged belt. The keyway is not a slot anymore, but a valley. I would appreciate any suggestions, besides don't touch my truck anymore. Thanks...

 

[Doc2012]

Pics??

Sounds like to MIGHT need a new crankshaft, which is $$$. Find a used engine, then let me have that one.

 

[Benski]

It is actually only moderately damaged. I am going to JB Weld a new key in the keyway and use a new timing gear, hb, and bolt and hope that works. This seems to have been a fairly common problem on Mazda Miatas. I have seen and read many repairs to them being done this way. If it lasts until the next time I get in there for a timing belt change, and I have to do the repair again, I will be very happy. Here's hoping...

 

[shadyluke]

It is actually only moderately damaged. I am going to JB Weld a new key in the keyway and use a new timing gear, hb, and bolt and hope that works. This seems to have been a fairly common problem on Mazda Miatas. I have seen and read many repairs to them being done this way. If it lasts until the next time I get in there for a timing belt change, and I have to do the repair again, I will be very happy. Here's hoping...

But if it only lasts long enough to leave you and your family stranded on the side of the road in a snow storm after you trashed the head and it won't run to keep you warm you will wish you just replaced the cam.

 

[danmac]

Jb weld is not going to hold that like it should. What I would do is either weld up the damaged area then have it milled out to accept a new key or just weld the key in it and trim the excess. Or if you can't do that have a machine shop or buy a new crank. Their is no cheap way to fix it right. And if your going to buy a used crank from a junk yard hop on the net pull specs and take a micrometer with and inspect the crap out of it. Sorry for your pain man I did timing chains on my mustang way back when I was young and knew everything in the world and got it 180 degrees off on the crank side. Needless to say the most expensive screw up to date, all bent intake valves and broke one off and put it through a piston.

 

[nevada]

if you can get the key to stay in place until the HB is slid on, it will be fine. the torque from the crank bolt will keep everything in place.
assuming you get it tight enough this time.

 

[Nelsonmd]

Jb weld is not going to hold that like it should. What I would do is either weld up the damaged area then have it milled out to accept a new key or just weld the key in it and trim the excess. Or if you can't do that have a machine shop or buy a new crank. Their is no cheap way to fix it right. And if your going to buy a used crank from a junk yard hop on the net pull specs and take a micrometer with and inspect the crap out of it. Sorry for your pain man I did timing chains on my mustang way back when I was young and knew everything in the world and got it 180 degrees off on the crank side. Needless to say the most expensive screw up to date, all bent intake valves and broke one off and put it through a piston.

Agreed. I would lean towards having a good welder tack in a key. The shaft is probably heat treated, so welding is going to ruin the heat treatment, so I wouldn't build the shaft back up by welding.

Just tack in a new key, putting as little heat into it as possible. TIG or MIG will also probably be better then arc or Oxy-Acy, as they will put the least amount of heat into the shaft. That or replace the shaft...

That sucks about the Mustang, definitely a mistake you won't make twice. Our 4runners are somewhat immune to that since they're non-interference, so that's nice.

 

[Benski]

if you can get the key to stay in place until the HB is slid on, it will be fine. the torque from the crank bolt will keep everything in place.
assuming you get it tight enough this time.

Oh it'll be tight THIS time! I'm going to use the bolt with the washer for the 99-02s and torque it to 217 lbs. That with the JB Weld repair and new parts I hope will work.

 

[nevada]

Oh it'll be tight THIS time! I'm going to use the bolt with the washer for the 99-02s and torque it to 217 lbs. That with the JB Weld repair and new parts I hope will work.

it will be fine. the key is only there to keep the HB from spinning on the crank. of there is any key catching, it will do that. you only need it to stay in place until the HB is fully seated. in fact, only until the HB is started, after that it will hold the key in position.

 

[danmac]

That sucks about the Mustang, definitely a mistake you won't make twice. Our 4runners are somewhat immune to that since they're non-interference, so that's nice.

Lol yea that was a hard lesson to learn. But as soon as I stop being lazy and finish building my spare motor for it I can sell it and get me a 3rd gen. this mustang has been a huge money pit, had a termi swap in it for a good while then had a oil pump fail on it I'm just sick of working on the ford 4.6 engines.