Crank shaft smoothing?

[1986gt-s/coupe]

I have a first gen 3s-ge and one of the rod berings went, could i if so how much would i have to sand off the crank before using a plastigauge?

[93celicaconv]

Is the crank bearing surface scored from the failed rod bearing? I'm assuming it is, if you feel a need to sand it.

Do you have the crankshaft out of the engine? Or are you thinking about sanding the crank bearing surface when the crank is still in the engine?

[Bitter]

it needs to be resurfaced by a machine shop or replaced if there any galling, scoring, scrapes, or damage. rule of thumb is if you can see it and your fingernail will catch it (or a saftey pin needle) then it needs to be repaired professionally. the 3S-GE is a high revving engine, any bearing issues not fixed right will rear back up at the worst time and cause nasty problems later on.

[93celicaconv]

Bitter is absolutely right, I just wanted to see where you were going with your thought process. I was sort of thinking you intended to sand off the galling with the crankshaft in the engine. Won't work, if that is the thought. First, you cannot sand it to be perfectly round. You likely won't get the finish needed on it either. And you certainly won't get to the proper tolerance on the diameter to fit an oversized bearing on it properly. Only a machine shop can to the process right, and tell you the new bearing surface diameter and what your new bearing sleave size needs to be, if there is any imperfection at all.

[1986gt-s/coupe]

So i used emery cloth and smoothed it out, there was no major score's, polished it to a mirror finish, and plasti gauged it the result was .002. the standard bering fit and it is running strong. All done with the engine still in the car. But i was ripped off when i bought it. The berings cost $59. Is it still a bad deal or a good car?

[93celicaconv]

Time will tell. I can't imagine a rod bearing fail and not causing some scoring of the journals. If there was none, you wouldn't have had to use emery cloth to polish anything. How you got 0.002" clearance all the way around (meaning your sanding process yielded a perfectly round journal) also seems impossible to me.

I tried this one myself, when I didn't know better. I had a rod bearing going out because of residual metal debris from a head rebuild that wasn't properly removed at the machine shop. I did the exact same thing you did, but I did not check it with the plasti gauge (so you are one up on me there). New rod bearings, put it back together, and it ran great, no more rod knock. I thought I fixed it too. Drove it around town for short trips a fair amount. Everything working good. Then took it on a 200 mile trip. Made it about 190 miles of that trip, and suddenly the rod knock came back. Slowly drove the last 10 miles, and it was knocking pretty bad. Towed it back home. Checked it out. That same rod bearing I just fixed up had failed.

So give your fix a shot. Maybe the stars were in alignment for you. Or you really know how to do machinists quality work with emery cloth. Either way, you may be fine. But something tells me whatever caused your rod bearing failure in the first place will come back again. I hope I'm wrong. Let us know what happens.

[1986gt-s/coupe]

My dad coached me through it, he's 33 years in to mechanics. It seems to be running fine, im running a 15-40 oil lol. All you haters saying its undoable, im 19 years old, and pretty stoked on what ive done, and yes it runs and drives, pulls all the way to 7000. Thanks for everyones help, and stop hating haters.

[93celicaconv]

1986gs-s/coupe, one thing I am not is a "hater".

I've been responding in these forums based on an ambiguous "average" of individual capability. In these forums, people’s ability to do certain things runs the enter range of capability, and I would have no idea what the capability of any particular person at the start of a thread is. Wouldn’t know how to do that.

But I can tell you this – automotive engine repair has changed a lot over the years. In the 1950’s and 60’s, and even into the 70’s, engine tolerances were pretty huge (and that is partly why it was so rare for any engine to last 100,000 miles without a rebuild). Repairs like you just did with your dad were a lot more common, because things were made to work that way back in those days. Mechanics with “average” ability on up could do these kinds of repairs just like you and your dad just did.

But today, engine tolerances are extremely tight, with very little margin for error. That also is partly why engines today can easily get to 300,000 to 400,000 miles without significant repairs. Because of how tight the tolerances are today, you don’t see repairs done the way you and your dad just did, because the average mechanic’s ability is no longer good enough for that kind of repair to work. Even very good mechanic’s abilities are no longer good enough. So today, you don’t find this kind of repair technique acceptable anymore. Most repairs like this are done as stated by me and others within this thread to get the repair done right.

That said, there can be that very rare, and highly talented mechanic that still exists in this world today who defies the odds, retains the “hands-feel” skill, and can actually make the kind of job you just accomplished actually work. That person is your dad. There aren’t many like him in the world today, for sure. You are so fortunate to have someone with his rare skills around to be able to coach you and show you how it is done. And you are pretty rare yourself, son, to have the patience to learn from someone as talented as your dad. You should feel proud about what you were able to do, but even more so, thankful you have someone like you dad with his exceptional skills, who is willing to take the time to share his skills and knowledge with you.

You and your dad are probably one in a million who could do something like this. I wasn’t responding based on knowing you two had this kind of capability, as most users of these forums don’t. So, I have no hate, not at all. Just respect where I was coming from. I certainly do respect the ability of your dad, the world could use more people like him, and do your best to keep learning from such a great teacher.

[1986gt-s/coupe]

Sorry man, i wasnt refering to you at all, you've helped me out and i thank you for that. And he is one in a million. I ment no disrespect to you at all, sorry.

[Bitter]

used crocus cloth I hope, not emery cloth?