Conrod bolts and nuts: Replace or not?

Luis A.

Luis A.

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So I'm struggling with this decision. The bolts and nuts look fine but are they stretch? The engine has relatively low miles, 84k.

If they are replaced, they need to be pressed out and the new ones pressed in. I've read that pressing bolts in and out can minutely affect the concentricity of the conrod leading to other problems if the big end is not resized. Is this a consideration for the M30?

Am I over thinking this...:confused:
 
Am I over thinking this...

YES!!!!!

I fail to understand what you are doing to such a low mileage E-3 when the bottom end on a reasonably maintained M-30 will go 250-300K miles. You are only i/3 or less of that.
 
If it was me I would reuse the existing. Perhaps a bit old fashioned but I was raised in the “if it ain’t busted don’t fix it” school.
The m30 is an old design, the bottom end is over engineered. A pro. mechanic friend says m30 bottom ends do not wear if looked after!
 
Luis A. said:
So I'm struggling with this decision. The bolts and nuts look fine but are they stretch? The engine has relatively low miles, 84k.

If they are replaced, they need to be pressed out and the new ones pressed in. I've read that pressing bolts in and out can minutely affect the concentricity of the conrod leading to other problems if the big end is not resized. Is this a consideration for the M30?

Am I over thinking this...:confused:
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Luis,
I'm pretty sure they are stretch but BMW's description leaves some doubt. With that said this was discussed recently here and almost everyone including engine builder Don Lawrence uses them again.
I changed mine and then ran into the resizing issue of the big bearing end. They get out of round.
So I would reuse them.
Gary
 
Hey Gary - Luis' post is nine years old. Aussiecsi resurrected this.

I think the reason there was so little discussion in this thread is that Murray Fowler said to reuse them, and he had an excellent reputation for coupe wisdom.
 
Ohmess said:
Hey Gary - Luis' post is nine years old. Aussiecsi resurrected this.

I think the reason there was so little discussion in this thread is that Murray Fowler said to reuse them, and he had an excellent reputation for coupe wisdom.
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Pretty typical of me Chris. Don't look at the date. DUH!
Thanks,
How are you?
Gary
 
Pretty well. Finally getting back to some car work.

I just finished up installing the new bumper ends to go with the rechromed center, and shined up the car for a little photoshoot. Our community magazine is doing periodic features on the cars owned by folks in the community and they accepted my article. It should run in May. I did a joint thing with my buddy, so the article features two coupes. I probably should post this in the what have you done to your coupe thread!


20210301_150156.jpg
 
FWIW I reused mine on my recent piston swap with the recommendations mentioned above and by @stphers who guided this blind squirell along. If the bolts decide to come out through the oil pan or block on the way to the Vintage I'll let y'all know :D
 
Ohmess said:
Pretty well. Finally getting back to some car work.

I just finished up installing the new bumper ends to go with the rechromed center, and shined up the car for a little photoshoot. Our community magazine is doing periodic features on the cars owned by folks in the community and they accepted my article. It should run in May. I did a joint thing with my buddy, so the article features two coupes. I probably should post this in the what have you done to your coupe thread!


View attachment 112807
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Looks great Chris. Hope to can come to Big A sometime with it. I have plans for something in the fall. You will see it soon on the email blast from BMW Classics of Georgia.
 
HB Chris said:
Chris, Sounds like a great article for Dirk and the CCCA quarterly magazine.
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Chris - I sent to you a copy of the article. It is something of a blend between an introduction to the coupe and an introduction to the owners (Tom Baruch's car is also featured), so it may need some tweaking for the CCCA. Check your email.
 
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