Ben16SS

Got my engine back from the machine shop. Started measuring my crank. They said it was just polished. After measuring my crank I’m consistently getting 2.0775 to 2.0774 on my Rod journals. I’m not experienced with this kind of work but am I wrong that 2.100 is the factory Rod journal size on an Ls crank? With my new bearings in my rods I am reading .0035 bearing clearance I want .0025. Am I missing something? Please help and thanks in advance.

strutaeng

Well you know, I also have a 5.3 crank polished. The machine shop recommended this little shop and that's all the guy does there. I have not actually measured the crank journals or "mic'ed" it. 🤔

I'm assuming you are measuring with a dial bore guage the direct clearance? Can you get non-standard bearings to make your target clearance? You can mix-match different bearings to get there, but I don't recall what the rules are and you have to buy 2 sets.

Ben16SS

Yes I am using a bore gauge. Like I said I’m a complete newb at all this stuff. I think if I use a .001 undersized or oversized not sure which…bearing it should work I’m just hoping someone with more knowledge can confirm that for me before I throw more money away hahah.

grinder11

iTrader: (1)

Are you 100% certain the mic is reading accurately? Still, hard to imagine its .023" off!! Especially since you've bought standard bearings, I'm assuming, and you have .0035" clearance. I believe they sell .001" undersize bearings. That's where I'd look next. I'd say it sounds like the crank throws are ground undersize, but your clearance with the standard bearing sizes are too close for the crank to be -.020". To try and clear up confusion on under/over size bearings, if your crank is ground smaller (undersize), you need smaller (again, undersize) bearings. Yes, the shells themselves must be slightly thicker to compensate for the removed crank material, but the inside diameter is smaller to match the cranks smaller throws (or mains). At least, thats the terminology I have seen in my part of the country, and the terminology used in the Toolroom I worked in. My .02..

Che70velle

iTrader: (6)

You are correct in assuming the crank should be 2.100. When polished, it might read 2.0999 to 2.0991ish. That crank has been cut. Might have happened to the owner before you, and the shop didn’t catch it? (Gasppp) You need to use an outside mic to measure that crank before you assume anything else. Even a Harbor Freight set will get you close enough to make it run a long long time.

01CamaroSSTx

iTrader: (3)

What are you using to measure the rod journals and have you checked the micrometer? If you would be so kind as to post a picture of this measurement for us.

Ben16SS

I have checked my mic to it’s standard and it zeroes out. I have measured each journal a whole bunch of times to make sure I’m not messing up and I keep getting the same measurements.just double checked with my bore gauge and I have .0035 clearance on my Rod.

Ben16SS

I am using an outside mic and have checked that it zeroes to its standard and it does I’m gonna post a pic of the mic reading here in a sec at the request of another person.

Ben16SS

I just rechecked zero and it’s perfect. Measured Rod journa #1 again and got 2.0775 unless I’m completely reading this wrong.

01CamaroSSTx

iTrader: (3)

I'm reading 2.09 somthing. Now look at the 1-9 numbers on the side to see what lines up with a line on the thimble screw.

Ben16SS

I had a feeling I might be reading this wrong. The 1 lines up so that .0001 right ?

01CamaroSSTx

iTrader: (3)

Each one of those lines past the zero is 0.025 and you are almost to .10 so it's definitely larger than 2.075 and closer to 2.10.

Ben16SS

I was thinking that after you pass one of the .025 lines you then add the next number on the thimble at .00xx and add them. So I was starting with 2.075 + .0024 then + .0001 for the line up of the finest graduation. Should I be adding .024 not .0024 is that what I’m goofing up?

01CamaroSSTx

iTrader: (3)

First short line past the zero is 2.025 then the taller line or midpoint is 2.050 then the third line makes 2.075 and finally the 1 which is 2.10. You came in short of the 2.10 by .024 due to the thimble reading of 20 then 4 lines past that which makes .024 so it looks to me like you're at 2.099. Does this make sense at all?

Ben16SS

I’m getting 2.075 +.024 +.0001 so 2.0991. Thanks for working with me on this by the way I really appreciate you!

01CamaroSSTx

iTrader: (3)

Okay now measure a main journal and see what you find.

RonSSNova

iTrader: (3)

For a sanity check, just use a digital caliper. Reading a .0001” vernier micrometer can be confusing if you don’t use them all the time!

Getting accurate measurements to .0001” really takes the correct “feel”.

Ben16SS

I had to leave the house. But I was getting really close to 2.558 as I recall I wasn’t having any second guess about the mains. Just confused as to what bearings to get to increase clearance because I was getting .0015 with my bore gauge and I’d like .0025.

Ben16SS

good idea I have a dial caliper I’ll double check with it when I get home.

01CamaroSSTx

iTrader: (3)

No problem and glad to help. Just throwing that out there about the mains so you could confirm you were reading the tool correctly.