crank rod journal: how big of a scratch requires a regrind?

[dreamweaver13]

I was mic'ing all the journals on my crank today so I can figure out what standard Toyota bearing to get. As I was removing the mic from one of the rod journals, I left a noticeable scratch. I can feel a slight dip with my fingernail. All my rod journals are at the lower limit for use with standard bearings right now, so I can either use it as is, or have it ground for an oversize bearing.

All little scratches are just specs of dust that seem to collect on the journals.
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[Doward]

If you can feel it with your fingernail, I'd have it reground.

And maybe knife-edged. And maybe... well, you know how this goes

 

[da89soup]

Yep time for the machine shop!!!:icon_bigg

 

[MKIIINA]

regrind. the crank is out already and regrinding isnt that expensive so ya may as well do it right once than twice incorrectly

 

[MDCmotorsports]

Little advice:

Take an older penny (like 1970s or earlier penny) and scratch the journal. If it leaves copper behind, the crank MUST be reground.

Either way, the crank is out, go get it ground & pollished.

 

[pimptrizkit]

oooo, time to polish, balence, knife endge.. lighten the crank! lol

:evil2:

 

[supra90turbo]

what pimp said.

 

[suprarich]

Regrind and might as well add 6mm of stroke too
J/K I just did not want to be left out of all the "do this too" stuff

 

[dreamweaver13]

...Actually it's time to go 2JZ with the HKS stroker crank...

I'm trying to figure out where to get bearings and what dimension I have to grind the journals to. I understand I can get .010 or .020 oversized bearings, but I'm not sure how to work out the final diameter of the journal. In the TSRM, http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?Section=EM&Page=70
there is a range of .0009 for use with std bearings. Do I subtract .010 from the biggest or smallest dimension. I guess I'll call around tomorrow. I haven't had any luck finding dimensions online. Clevite doesn't even have the 7M in their 2006 catalog.

how much should a regrind cost - $50? $100?
I'm definitely gonna take my time and make sure everything is perfect so I don't have to rip apart the engine again.

 

[pimptrizkit]

i forgot to mention, i had done that to my crank, thats why i had it polished,

 

[suprarich]

...Actually it's time to go 2JZ with the HKS stroker crank...

I'm trying to figure out where to get bearings and what dimension I have to grind the journals to. I understand I can get .010 or .020 oversized bearings, but I'm not sure how to work out the final diameter of the journal. In the TSRM, http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?Section=EM&Page=70
there is a range of .0009 for use with std bearings. Do I subtract .010 from the biggest or smallest dimension. I guess I'll call around tomorrow. I haven't had any luck finding dimensions online. Clevite doesn't even have the 7M in their 2006 catalog.

how much should a regrind cost - $50? $100?
I'm definitely gonna take my time and make sure everything is perfect so I don't have to rip apart the engine again.

Clevite has bearings for the 7m in their catalog, you can even view them online in pdf format. don't say oversize, the correct term is undersize and toyota bearings are sold in mm sizes. std, -.25,-.5,-.75,and -1mm

Don't buy bearings to match your crank, you buy the bearings and then grind your crank to match them. Plastic gauge the oil clearence, don't try to do it with mics.

 

[dreamweaver13]

thanks for setting me straight suprarich - I don't know what I was thinking when posting that.

I guess my question is how a machine shop matches the crank to the .25mm undersize bearings. I would think they mic the inner diameter of the rod and the thickness of the bearing, add it all up with the desired oil clearance to get a crank journal dimension.

 

[suprarich]

What they should do is look up std size of the journal and mic it. Compare std to the actual size to see if std size will work or if the next undersize is needed. If an undersize is needed then the appropriate amount should be ground off the crank on the tight side away from std size. The crank should then be installed into the block with all the new bearings. Plastic gauge each main and rod cap using your new fastener hardware. Compare the actual oil clearence that the plastic gauge is showing to your desired clearance. Disassemble and adjust any crank journal that is too tight by regrinding some more, or polishing for extreme small amounts. Remember, and most domestic machine shops will not know this, that toyota used up to 3 diffrent size bearings on the rods from the factory. Your new bearings will all be the same size, for that reason a regrind is needed anyhow. Unless you want to buy a bunch of diffrent size bearings. Treat each main and rod journal as their own job, one at a time. Don't set clearance by doing math, use the plastic gauge. Don't let them set up the whole bottom end by measuring just one journal, make sure that each journal is treated by themselves. You need to do it like that because you are dealing with measurments to 4 decimal places