Musings from the shop
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Okay, so here's my engine rebuild timeline so far...
March 3 - Ordered JE pistons through Top End Performance. Estimated 3-week lead time.
April 15 - Received pistons.
April 16 - Dropped pistons and block off at Automotive Supply to have the block bored. Was informed that they had gotten busy so it might take a week or two for them to get it done.
May 5 - Voicemail from Automotive Supply asking me to call them back.
May 6 - There was a problem with the tooling (or something...) and my block is wrecked. Agreed to sell them the other block that I had. Dropped 2nd block off the same day.
June 3 - Received voicemail that my block is done.
June 4 - Picked up block. Hone job looked like shit. Put a ring in each bore to measure the ring-gap and 3 of the bores were tapered. The tops of three bores were ~.002" undersized, but the middle was the correct size. The forth bore was .002" undersized with no taper.
June 5 - Brought block back to Automotive Supply. Jason, the "machinist" was off so I'd have to wait until Monday to talk to him.
June 8 - Stopped at Automotive supply to find out what he was planning to do with my block. He hadn't looked at it yet, but said he'd look at it and call me later that day.
June 10 - Having heard nothing I went back to find out what was going on. They said it was done and gave me my block back. The bores are a fuzz larger and no longer tapered, but one bore is ~.0025" larger than the other three.
TLDR: It took Automotive Supply 2 months to bore a block, they destroyed one of my blocks in the process, and they did a shitty job. Not recommended.
First time I got it back. Aside from the "crosshatch" there was a lot of horizontal marks. That combined with the taper makes me think that they probably didn't bore it at all, but just hogged it out with a hone. Vertical lines are from the bore gauge.
It looks a little better now, but still not good.
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I don't know the specifics of this particular bmw block in terms of the outer limits of boring out, but I personally would not be comfortable with a difference like that. Engine building is a precision exercise, plain and simple. You need a shop that's gonna measure and check to a tee. Anything less is risking premature engine failure. If you use what you have, you're going to have to re-calculate your expected compression from the bigger bore on one cylinder and build around that (depending on your performance plans), and higher risk of cylinder wall failure depending on the tolerances of the block (again, I'm not aware of the specifics on your motor). But these are generally things I would be worried about. If one cylinder isn't to proper spec for the JE pistons you're using, the larger bore is going to be a higher risk for blowby and premature wear on your ring and bearing in that cylinder.
i dunno. I just don't like there to be anything inconclusive about my block before I put it back together.
2011 E92 M3 6MT ZCP - ESS 625 supercharged
2007 Z4MR
2003 E39 M5
2002 E46 M3
2021 X5 40i -
I agree that it's far from ideal, but I want to actually drive the car this summer. Specifically I have a vacation planned for mid July, so I'm in a hurry to get it done. I'm also renting shop space, so every month that the car sits there is more money out the window. Worn out cylinders can easily have .005" of wear, sometimes substantially more, so basically I'm starting my rebuild with one bore that's half worn out. It suck, but given the circumstances, I'm just going to deal with it. As long as the pistons don't get wrecked I can get a new block and do it right next year.
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Okay, so I left some details out of the story. I've been planning on "someday" taking the car out west on an extended vacation. See the sights, drive some cool mountain roads, and use the free time and the open spaces to gain some perspective on things.
I recently put in my notice and am quitting my current job, however I haven't found a new job yet. I haven't been too worried about it because I have enough money saved up to keep my bills paid for a couple of months, so...... I made plans to visit a friend of mine in Denver for a week or two in mid-July. Basically, with no income, the sooner I get on the road, the longer I can stay on the road before I have to come back and find a job. Getting an engine, dismantling it, and waiting around hoping that a shop will turn my block around quickly aren't very high on my list of things I want to do right now. The opportunity for me to do this is here right now, and I'm not going to let a couple thousands of extra bore get in the way.
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Honestly at that point I would buy a clean stock m42 and pop it in there quick. couldn't imagine it being expensive. certainly less than ruining a set of forged pistons.
I was thinking the same, find a temporary motor that eventually can be used for parts too.
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I doubt it=/ Sorry to hear bud. Maybe they really hate m42's like everyone else besides you and I
And me!
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Sucks that you seem to have gotten the short end of the stick in this situation. I've been to Automotive Supply for things before and have never been impressed. After reading this, I'll make sure that no one I know will ever go there. Not acceptable. I don't think you should have needed to pay for any of that work. If anything, it seems like they should owe you.
I understand your unique situation and I'd just go with whatever feels best. Sounds like you've already made up your mind and I'd roll with it. Rebuild it later (if needed) when you don't have the opportunities that you do now.
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