crankshaft grinding on VG30DE

[Guest Haze89]

Hey Im about to finish my rebuild, but i, a bit worried about something, I grind my crank to 30( that how they call it here in PR) that means i have to wear .75 oversize bearings. The machine shop and everybody around here have said it can work and hold all the HP of my stock engine, they also said it is grinded at the maximum so it wont take anorther score. Im concern about it wont take another score but my issue is... will this crank hold normal driving without giving any troubles?

[Careless]

if the bearings are oversized to accomodate the added clearance, and it's brought back into spec, then it is essentially the same as a standard bearing on an untouched crank/bearing journal, because the clearances are the same.

 

all you're doing is putting metal where the bearing is now, and where the other surfaces used to be, making up for the added space that would be there otherwise.

 

at least that's the way i see it. Perhaps the thicker bearings will lend to some bottom end strength too.

 

if it's assembled as well as machined properly, the scoring shouldn't be an issue.

[Guest Haze89]

if the bearings are oversized to accomodate the added clearance, and it's brought back into spec, then it is essentially the same as a standard bearing on an untouched crank/bearing journal, because the clearances are the same.

 

all you're doing is putting metal where the bearing is now, and where the other surfaces used to be, making up for the added space that would be there otherwise.

 

at least that's the way i see it. Perhaps the thicker bearings will lend to some bottom end strength too.

 

if it's assembled as well as machined properly, the scoring shouldn't be an issue.

thanks man, i feel more secure now about doing this, by the wa i notice something in the crank and i dont know if its normal when grinding, in the journals edges the are two rails maybe some oil passages, those get grinded too and i can hardly notice, can i still use it like this???

[260DET]

Pictures?

[Careless]

thanks man, i feel more secure now about doing this, by the wa i notice something in the crank and i dont know if its normal when grinding, in the journals edges the are two rails maybe some oil passages, those get grinded too and i can hardly notice, can i still use it like this???

 

i think the rails you are talking about are to keep oil around the perimeter of the bearing so that the entire bearing is cooled rather than lubricated (you wouldn't need too much lube there), and the edges don't heat up from the inside out, causing the clearance to change rapidly.

 

the bearings are usually radiused along the edges rather than sharpened to a corner so that there's more oil clearance there too.

 

I think it will be fine. pics would help.

[Careless]

or perhaps you're talking about the retaining groove that holds the bearing in place with the tiny little piece of metal that holds the bearing into the groove? the grinding and the oversized bearing should account for all of that with a smaller retainer.

[Guest Haze89]

or perhaps you're talking about the retaining groove that holds the bearing in place with the tiny little piece of metal that holds the bearing into the groove? the grinding and the oversized bearing should account for all of that with a smaller retainer.

 

no thats no it, i was talking about the 6 journals in the crank that used to have 2 rails each, one in each side of the journal, and now they are mostly gone

[Careless]

are you talking about the ones on the very edges of the polished bearing surface on the journals in this picture? (Not the same engine, but a good reference image)

 

 

 

those are to ground to size and to be radiused, and they're probably ground down because the side clearance with the over-sized bearings could have made it too tight of a fit. when you cup a bearing halve around the journal, can you see a bit of space at where they *would* meet at the corner? (because they shouldn't meet flush, there has to be adequate clearance for oil to run out and around there.

 

perhaps a machinist can chime in? BRAAPSTER?