L28 Main Caos

[Racer X]

2 hours ago, Remixaflip said:

It’s a complete engine with all the pars except for the one missing main cap. I plan on doing a full rebuild any so doing having a machinist line bore the cap to fit isn’t a problem, I’m just having a hard time finding the one cap. I managed to get to engine for $500 dollars.


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Is it also missing the bolts for the missing bearing cap?

[Remixaflip]

Okay, so you just need to find a junked motor and steal the caps off it. Might be a hard find. See if you can find a cheap F54 block on CL or a salvage yard. Where do you live?


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I live in California.


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[Remixaflip]

Is it also missing the bolts for the missing bearing cap?

Yes, I planned on buying all New hardware anyways.


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[Terrapin Z]

I have a full set of caps off a 260 motor I'd sell. It was sitting outside for a little bit so there is some surface rust on the outside. They are still bolted down though. 

 

[Captain Obvious]

11 hours ago, Remixaflip said:

I plan on keeping this car for a long time. Maybe I misunderstood your statement. When you said you have an f54 block, we’re you referring to the complete block or just the mains?

OK.

I've got a whole F54 setup here... Block, crank, caps... But the block block casting itself is no good*, so I don't mind selling the caps off separately.

The crank is also available to a new home if anyone is interested (shipping prohibitive).

*There was an ummm....  mishap during the rebuild process. I believe the technical term is "oopsie".

[Zed Head]

Seems like a good time to think about how main bearings work.  Materials, sizing, all that stuff.  I remember learning how to use Plastigauge in high school auto shop but I don't have many memories of what to do if the numbers are off.  Seems like all of the videos I've seen all have good results, nobody ever gets a bad number and has to fix it.  Plastigauge has always seemed more like a confirmation tool than anything else.

It would be interesting to know what people do if they get a bad clearance.  Can you knurl a bearing seating surface to shrink a wide clearance?  Seems like it should work.

How do you tell if the bearing is square in the seat?  If Remix tries different cap does he need to worry about squareness, or concentricity or roundness?  Do any of those change over the of of an engine block?  Don't know, just asking...

It might be that manufacturing QA was good enough in the 70's that caps are swappable.  Who knows. 

Found a couple of links.  Looks like one "borrowed" from the other.  

https://www.substech.com/dokuwiki/doku.php?id=engine_bearing_materials

https://www.chevyhardcore.com/tech-stories/tech-choosing-the-proper-bearings-for-your-engine/

[240260280]

1. Buy a set of caps

2. Buy a bore gauge.

3. Match the best cap.

4. Fit bearing

5. Confirm diameter and concentricity

6. Triple check bearing squish when assembling

 

[Reptoid Overlords]

https://sfbay.craigslist.org/eby/pts/d/dublin-datsun-240z-260z-engine-block/7308756529.html

Maybe you can salvage this one.

[Reptoid Overlords]

Just now, Reptoid Overlords said:

https://sfbay.craigslist.org/eby/pts/d/dublin-datsun-240z-260z-engine-block/7308756529.html

Maybe you can salvage this one.

But it's prob a 2.6?  He hays 240z/260z in the ad.  maybe worth checking if it's a 2.8 and he doesn't know it..

[Racer X]

All L series engines have the same main bearing journal diameter, so a bearing cap from any L engine will do. A competent machinist can fit the cap, then line bore the assembly.

Bearings are available undersized for use when turning a journal has to be turned to clean up wear or damage. Bearings are also available oversized for use when line boring is required.

Journals cannot be knurled like valve guides to correct clearances.

 

Edited April 22, 2021 by Racer X

[Zed Head]

1 hour ago, Racer X said:

Journals cannot be knurled like valve guides to correct clearances.

I'm sure that you realize that any good machinist who heard you say that would take that as a challenge.  Machines are just metal formed to do what we want it to do.  There are pros and cons to everything.

https://www.practicalmachinist.com/vb/general/knurled-bearing-fit-how-engineer-324497/

If the machinist has to work on it then does it really "do"?  A good machinist could just copy one of the existing caps to steel and get a perfect fit from the start.  Remix doesn't even need a used part.

1 hour ago, Racer X said:

All L series engines have the same main bearing journal diameter, so a bearing cap from and L engine will do. A competent machinist can fit the cap, then line bore the assembly.

 

[Zed Head]

For the record, I just swapped a spare engine in to my car because I had one and did not want to rebuild the head on the engine that was in it.

These things depend on what the owner is trying to accomplish.