Engine build questions,, Bedplate???

thomsenski

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Mar 16, 2018
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Ive been looking though old posts but haven't found what I'm looking for,
Someone told me I need alignment jig for bedplate?
BMW doesn't say to use one,
bedplate is has locating dowel pins. anyone build there own run into this.
I'm new to this world and only had the car for short time before motor went,
 

The Convert

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You have to have an alignment tool to align the bedplate to the block correctly or you'll have a bad day. You can rent the tool or build your own prior to removing the bedplate if you have some fabricating skills.
 

thomsenski

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Mar 16, 2018
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So why do you need an alignment jig. BMW doesn't say anything at all about one.
So what if you take the bedplate off before?
 

The Convert

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If you take the bedplate off and have no alignment jig, you're fucked. The bedplate splits on the centerline of the crank mains. If you don't have it to properly align the bedplate when putting it back on, your alignment will be off and you're crank will very likely sieze or spin a bearing very quickly.
 
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The Convert

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Also, BmW absolutely does mention its use, as I have seen pictures of it from either a manual or a print out posted on one of the other forums. Plus, it's been a topic of discussion for years with newcomers to the platform.
 

E92 420

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Also, BmW absolutely does mention its use, as I have seen pictures of it from either a manual or a print out posted on one of the other forums. Plus, it's been a topic of discussion for years with newcomers to the platform.

Never ever seen bmw’s Own tool or seen mention of it in any manual! However it is common knowledge that an alignment tool of sorts has to be used. Only ever seen ones fabbed up by DIY’ers I know ABR Houston have there own design too.
 

pysical

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Everyone always says you need one. My engine was built without one. Crank spun easily after torquing the bed plate down.
 
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Tuppidsay

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Ive never done it but Ive also heard about a fixture for the bedplate. Since i saw this thread I went to look it up and neither article mentions anything about a fixture. I looked these up using a 2008 335i Coupe for referance.
 

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thomsenski

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Mar 16, 2018
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I've looked up the exact procedure in BMWs manauls and it mentions nothing at all of a jig.
And maybe I'm just a retard but your guys so called alignment jigs. Looks like a joke and honestly I can't believe your alluminum plates your bolting too it will make any difference at all.
The machine shop and me where both looking at the block and can not understand at all how your so called jigs would ever work. And I contacted a machinest that builds these and does it every day and has never used such a thing.
I guess I'll take my chances and follow the workshop manual. Its never failed me befor. Ive been a master technician for 15 years. So call me stupid. I don't care. I honestly can't belbeli that that jigs that I'm seeing pictures if could ever make a difference on anything. The dowls pins are going to put the bedplate into place.
Your jigs are not going to change anything on the alignment.
And BMW does not say anything about a jig
And I repeat!!
BMW says nothing if this in there workshop manual.
 

doublespaces

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I've looked up the exact procedure in BMWs manauls and it mentions nothing at all of a jig.
And maybe I'm just a retard but your guys so called alignment jigs. Looks like a joke and honestly I can't believe your alluminum plates your bolting too it will make any difference at all.
The machine shop and me where both looking at the block and can not understand at all how your so called jigs would ever work. And I contacted a machinest that builds these and does it every day and has never used such a thing.
I guess I'll take my chances and follow the workshop manual. Its never failed me befor. Ive been a master technician for 15 years. So call me stupid. I don't care. I honestly can't belbeli that that jigs that I'm seeing pictures if could ever make a difference on anything. The dowls pins are going to put the bedplate into place.
Your jigs are not going to change anything on the alignment.
And BMW does not say anything about a jig
And I repeat!!
BMW says nothing if this in there workshop manual.

So what is the status of this?
 

Bnks334

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You have to have an alignment tool to align the bedplate to the block correctly or you'll have a bad day. You can rent the tool or build your own prior to removing the bedplate if you have some fabricating skills.

Not sure why people and engine builders are saying this... It doesn't even makes sense. Take a look at the bedplate prior to removing it. There is nothing externally visible to "align" the bed plate to with the accuracy people are claiming. There is noticeable overhang on all sides of the block. I doubt the external measurements of the block casting are accurate to within 1/8" let alone .01." There is no way any jig is helping here. The stock dowel pins do a great job of getting everything lined up and the final torque sequence will shift things into their "exact" natural position no matter what you jig the bedplate with. That is reality and this is not nearly as complicated as people seem to want to believe.

"How do you know the bedplate is not off .01" or even .001?" Well, to that I ask, how the hell does bolting some flimsy aluminum bracket to the side of the block ensure any kind of accuracy down to even .1" lol... I can guarantee any "jig" people use is doing more harm then good unless they are creating a new one EVERY TIME they build a motor (not a chance). You think BMW "laser-aligned" the bolt hole orientation you're using to bolt your jig to? You think those bolt holes are in the same position on every block within .001?"
 
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Rob09msport

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Is their any play when the dowels are seated but the bolts not tight ? Seems like pretty big deal to make sure don't get it wrong
 
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Bnks334

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Is their any play when the dowels are seated but the bolts not tight ? Seems like pretty big deal to make sure don't get it wrong

There is no "perceptible" play is all I can say. The crank/bearings pretty much lock the bed-plate in place when you put it on. You can't move it by hand at all and definitely not with any kind of precision.

The crank rides on bearings not the bed-plate... axial play is engineered into the design and gets measured AFTER torquing down the bed-plate. You fall within spec then you aren't mis-aligned! The idea that you need a special jig to get this alignment right makes no sense. You shouldn't be worried about lateral play either because the bearing shells themselves are basically springs which "crush" against one another and spread open to create a perfect circle (it's technically an oval shaped opening) for the crank to ride on. The final torque sequence accomplishes this, not a jig. Anyone building an engine would be bolting down the bed plate and bearings, with no crank in place, to measure eccentricity and ensure a line hone isn't needed.

You don't use a jig to put aftermarket rod caps on, do you? It's the same thing... you rely on the dowel pin to locate the cap and then the final torque crushes the bearing shells into place giving the cap, and the rod bore, its alignment and eccentricity.
 
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1985GSL

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8 year BMW Master tech here... I did several n52 block and piston replacements under warranty, and built my n54 with pistons, rods, bored over blah blah and there is no such thing as a BMW special tool for bedplate alignment(although its hard to believe).
 

JimmyNeutron

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I remember reading on the "other" forum about ABR Houston pushing the idea that their proprietary alignment process is absolutely necessary because the N54 is robotically assembled and that no human can replicate assembly and achieve factory tolerances... except for ABR. ABR claimed that the main journals would have to be line honed if no jig was used. They also said the assembly procedure in the factory's service manual was adequate for stock power levels, but not for anything more.

That all sounds a little far fetched to me. For those who are running a built motor who did not use a special alignment jig, how much power are you running? Any problems?

I would think there would be a lot more "Yep, it blew up/spun a bearing/whatever because I didn't take it to ABR" stories out there if ABR's claims are true. What about those running MMP or Motiv engines? Haven't heard a single story involving bearing failures due to bedplate misalignment.
 

[email protected]

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Few things-
1. some things were taken a little out of context.
2. Main studs cause all sorts of issues with block flex and movement.
3. Straightening a line bore in a NG6 block is incredibly complicated, but we've perfected it.
4. We do have a proprietary way of fixing the block, no I won't divulge on how it's done.
5. No, I'm not going to show you a picture of our block and bedplate alignment jig.
6. When putting the bedplate on the block, there's absolutely movement in the two components, and alignment is critical. You're literally using the crankshaft to center the main bearings shell to shell, if not.
7. Even with machined dowel pins that are oversized to eliminate any movement, alignment issues still arise. We've seen it.

Just because BMW didn't build a tool (I know, funny- they build a tool for almost everything) doesn't mean that making or designing your own tooling isn't going to happen. We have built multiple tools to help build these engines, along with day to day tools we use for our general repairs.