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Measuring Journals
https://www.slantsix.org/forum/viewtopic.php?t=50589
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Author:  jhdeval [ Mon Dec 17, 2012 9:31 am ]
Post subject:  Measuring Journals

Okay so I found out today my micrometer does not have precision to .0001 so I know I can not use it to get an accurate reading but I did take a rough reading.

The service manual says:
Main Bearing Journal Diameter: 2.7495 to 2.7505

I read from front of block back:
1: 2.760
2: 2.746
3: 2.751
4: 2.749

I think I may not have closed the micrometer enough on number 1 and maybe 3 also I am not sure if the micrometer is rounding. I am looking for a .0001 micrometer but based on what is seen here should I expect to have the crankshaft worked?

Author:  CNC-Dude [ Mon Dec 17, 2012 9:37 am ]
Post subject: 

The #2 journal, based on the specs you measured, is well under the low side tolerance for standard. You also didn't mention if the journals were round or out-of-round by any amount. Its more than likely going to need to be reground based on what the #2 journal measures. What condition are the rod journals in as far as what you have mic'd.

Author:  robertob [ Mon Dec 17, 2012 9:46 am ]
Post subject: 

You also need to measure at a couple of different points because journals wear oval.

If you are unsure, just bring it to your machine shop, usually they will check it for you for a few $$, sometimes even free if you are paying them to do other work.

Author:  jhdeval [ Mon Dec 17, 2012 10:50 am ]
Post subject: 

I did not measure the rod journals yet. I also did not measure in a couple of places although I did pull my mic back and forth across the surface to try and make sure I got a good reading.

I think I am going to bring it to my machine shop anyway. I want this to be a nice engine and like I said in my previous post I want to be able to pop off the line if I should choose to. I also recently picked up another head that I am going to have him work for me.

I am looking for 9.5 to 10 compression ratio. I am also considering some port matching and maybe polishing. If the cost does not skyrocket.

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