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Old 03-07-2014, 02:47 PM   #1
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Default Thrust Bearing damaged whilst Plasti-gauging main bearings - WTF? Weird

Gents,

I took the morning off of work to enjoy the (gasp) 50F weather in Ohio and start the assembly of my "built" motor.

Whilst plasti-gauging the main bearings I somehow managed to damage the thrust bearing. I bought all new bearings except the thrust bearing (because I'm idiot), so the bearing I damaged was the old 150k mile OEM one.

I know this post is useless without pictures, I will try to add some later. But anyway, I fubar'd the bearing by installing and pulling out the crankshaft.

Anyone ever seen that before? It's like it got caught at a weird angle by the crank and got chewed up while torquing the crank down. I didn't spin the crank at all, just put all the new bearings in, put the thrust washers in, laid the crank in and torqued down the main bearing caps. When I pulled the crank out there was what looked like a tiny piece of aluminum foil stuck in the number 3 cylinder bore. I picked it up and noticed the thrust bearing (washer) looked chewed up.

I guess the bearing fell out of the groove ever so slightly one of the times I was laying the crank in, and then when I torqued it down it "shaved" some material off of the bearing face?

I'm annoyed, and I'm just curious if anyone else has had this happen, and if my assumption of what happened is correct or if I have a more serious issue.

I ordered a set of Clevite thrust washers, I'll very carefully install those and measure endplay afterwards.

Pics forthcoming

Ughghghhh
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Old 03-07-2014, 02:56 PM   #2
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This concerns me, as I've got a pile of engine parts and will be doing this exactly sometime this month.

I honestly don't even know how the thrust bearing is supposed to be installed, and I'm really not any help. But pictures please! I'd like to know what NOT to do.
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Old 03-07-2014, 03:01 PM   #3
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See pics
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Old 03-07-2014, 03:03 PM   #4
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Ew, check that bottom end thoroughly to make sure no shavings ended up anywhere..
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Old 03-07-2014, 03:10 PM   #5
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Yeah, I've done it, but not on a Miata. Frustrating as hell to have to wait until the stores opened the following day to finish assembly. Pre-internet days, donchaknow.

Chance are, you lowered the crank in at an angle instead of straight down. At least that's what I think I did.
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Old 03-07-2014, 03:13 PM   #6
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Moar?
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Old 03-07-2014, 03:17 PM   #7
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That looks odd to me. I can see where you shaved it on the right, but are those bumps in the center supposed to be there?

Keep in mind I have never seen the inside of a Miata engine except in pics posted here.
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Old 03-07-2014, 03:23 PM   #8
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Last one for meow
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Old 03-07-2014, 03:29 PM   #9
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Quote:
Originally Posted by rleete View Post
Yeah, I've done it, but not on a Miata. Frustrating as hell to have to wait until the stores opened the following day to finish assembly. Pre-internet days, donchaknow.

Chance are, you lowered the crank in at an angle instead of straight down. At least that's what I think I did.
I think i might of bumped it out of the groove a little bit when lowering the crank. I did take the crank in and out three times, so I guess I was 2 for 3?

Quote:
Originally Posted by rleete View Post
That looks odd to me. I can see where you shaved it on the right, but are those bumps in the center supposed to be there?

Keep in mind I have never seen the inside of a Miata engine except in pics posted here.
The bumps are not supposed to be there...sort of. The bumps are portions of material that weren't removed. The "bump" areas are more representative of the original bearing face, or where it should be...
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Old 03-07-2014, 03:33 PM   #10
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Curious, what did your main bearing clearances measure out to ?
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Old 03-07-2014, 03:42 PM   #11
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I have pictures of all of this stuff I'll post in my build thread

BUT

to answer your question the spec is 0.0008-0.0014"

I measured 3 of the main bearings (1, 3 and, 4), and they were anywhere from 0.0010-0.0014" or so

My plastigauge scale bars were 0.0010 then 0.0015, so it was hard to get exact readings, but anyway they were all less than 0.0015 so within spec.
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Old 03-07-2014, 04:13 PM   #12
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Quote:
Originally Posted by Efini~FC3S View Post
I have pictures of all of this stuff I'll post in my build thread

BUT

to answer your question the spec is 0.0008-0.0014"

I measured 3 of the main bearings (1, 3 and, 4), and they were anywhere from 0.0010-0.0014" or so

My plastigauge scale bars were 0.0010 then 0.0015, so it was hard to get exact readings, but anyway they were all less than 0.0015 so within spec.
I'll wait for you to post it up in your build thread, but i do have more questions so I'll put em there.
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Old 03-07-2014, 05:37 PM   #13
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So....

I talked to a buddy of mine that has assembled a fair amount of engines.

He said the best way to avoid this is to not install the thrust bearings (washers...whatever) until after you lay the crankshaft in. Then after laying the crank down, you sort of fish the thrust bearings into place by some sliding and rotating shenanigans.

When he heard that I was installing the thrust bearings first and then laying the crank in he looked at me like I was a moron...

I guess I'll try this other method when I get the new thrust bearings in and I get to do this all over again. I'll report how that goes.

For now I'm going to thoroughly clean the block again to hopefully get any random aluminum shavings out.

#hatemyself
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Old 03-07-2014, 06:56 PM   #14
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Okay, third pic shows it much better. Yeah, looks like the end of the crank dug in and caught, then shaved the middle out. Actually, it looks like you might have caught it more than once. First time just cut/dug in, but the next one shaved the piece out.

Everyone screws up from time to time. It's called experience. Probably doesn't make you feel much better, but hey, **** happens.
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Old 03-07-2014, 07:28 PM   #15
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What year motor is this for? I have a few pairs for a 99+ motor I could send you for the low cost of shipping. Unfortunately they won't fit a pre-99 motor.
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Old 03-07-2014, 08:33 PM   #16
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Well, at least its only what, $30-40 mistake? Definitely could be worse and be glad you caught it now!
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Old 03-07-2014, 08:39 PM   #17
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$15 mistake (bought Clevite ones through amazon).

Honestly I got really lucky finding it. I forgot to install the oil squirters and had to take the crank out again to do that. That's when I noticed the thrust bearing was fubar'd. If I hadn't forgot to install the squirters I most likely wouldn't have caught it...
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Old 03-07-2014, 09:03 PM   #18
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Midtenn -- It's a 94 block, thanks for the offer.

I'm not mad about this whole deal, just annoyed by the ~5 day delay. It's okay though because I have plenty of stuff to keep me busy until then.

The main reason I wanted to assemble and build this motor was to learn...mission accomplished. I learned how not to install thrust bearings, and I'll learn how to properly check crankshaft end play too
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Old 03-07-2014, 10:49 PM   #19
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TRIPLE POST!!!

GTFO



Not that they are needed but more pics of the damaged bearing are here ---> https://www.miataturbo.net/build-thr...4/#post1109778

They are better...er

kind of
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