[DSRE455]

Arp 8740 99% with their lube is 63ft lbs, if your real tight on money, ARP HAS A NICE ONE
check the ra finish on those journals, Paul is the real deal

[DSRE455]

Originally Posted by redhawk44

Heres a pic of My Rear Main after about 5K miles. Any thoughts on whats going on here?

Crank needs to be redone, not every shop can do 3.25 main crankshafts. And that not going to last long at all

[redhawk44]

What are you seeing in the pic that tells you that my crank needs reground? I'm looking at and I think it looks good but I realize that I'm no expert. Are you talking out of round??

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[redhawk44]

I have a stretch gauge on the way . Should be here today. That's good info Steve on the guage it telling you that the bolt threads are sketchy.

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[steve25]

Yes, they should load to the needed stretch dimension fast, if not then they will act rubbery and that's the tip off that's replacement is needed!

[74Grandville]

problem i have seen with using a streach gage on rods that were not originally machined that way. You'll notice one rating will be different then the other, so your holes will be out of round. Streach gauge is the better way to do it to ensure proper even torque, but you may need to redo the hone.

[DSRE455]

Originally Posted by redhawk44

I have a stretch gauge on the way . Should be here today. That's good info Steve on the guage it telling you that the bolt threads are sketchy.

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Originally Posted by redhawk44

What are you seeing in the pic that tells you that my crank needs reground? I'm looking at and I think it looks good but I realize that I'm no expert. Are you talking out of round??

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Originally Posted by DSRE455

Crank needs to be redone, not every shop can do 3.25 main crankshafts. And that not going to last long at all

Rear main journal picture

[hurryinhoosier62]

Originally Posted by gtofreek

Yes, your crank journals have chatter marks from being ground too fast.

X 2! I’ve never seen anyone left a crank go with that much chatter marking Three possible causes for the chatter: 1.) too fast of a feed rate as Paul said. 2.) Too much coolant flow allowing the grinding stone to “skip”on the surface of the journal. 3.) a dull grinding stone. You should probably have a different crank grinder take a look at your crank for taper and O/R.

[hurryinhoosier62]

Originally Posted by redhawk44

Kind of hard to tell in this pic but the journals look good in person, to me.

I’ve ground over 2,000 cranks. If one journal is screwed up you need to check them all. Check the stroke while you’re at it.

[gtofreek]

Originally Posted by 74Grandville

problem i have seen with using a streach gage on rods that were not originally machined that way. You'll notice one rating will be different then the other, so your holes will be out of round. Streach gauge is the better way to do it to ensure proper even torque, but you may need to redo the hone.

Exactly! Most rod manufacturers DO NOT use the stretch method when they size the rod. If they did not, and you do, the big end bore will not be round anymore. I check every rod that goes through this shop and I see this all the time. Best to use the rod manufacturers torque method or take them to a shop and have them resized using the stretch method.

[hurryinhoosier62]

Originally Posted by redhawk44

What are you seeing in the pic that tells you that my crank needs reground? I'm looking at and I think it looks good but I realize that I'm no expert. Are you talking out of round??

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The finish isn’t right. A crank with as few miles as you said yours has should still look like a mirror IF it was properly finished. I can guess as to what happened: the grinder got in a hurry and left chatter in at least the rear main journal. When he discovered it, he tried to polish it out. There is just one problem: you can’t polish out chatter marks. The crank should have been reground to deal with the chatter. Another problem arises when you attempted to polished out chatter: you polish in taper.Do you have a micrometer eye? The maximum allowable taper in a V8 crank main journal is .0002(2/10th of 1/3 of a human hair). That is WHY this crank needs to be rechecked by a different crank grinder.

[redhawk44]

Originally Posted by hurryinhoosier62

The finish isn’t right. A crank with as few miles as you said yours has should still look like a mirror IF it was properly finished. I can guess as to what happened: the grinder got in a hurry and left chatter in at least the rear main journal. When he discovered it, he tried to polish it out. There is just one problem: you can’t polish out chatter marks. The crank should have been reground to deal with the chatter. Another problem arises when you attempted to polished out chatter: you polish in taper.Do you have a micrometer eye? The maximum allowable taper in a V8 crank main journal is .0002(2/10th of 1/3 of a human hair). That is WHY this crank needs to be rechecked by a different crank grinder.

Damn,
Okay well I have been emailing the manufacturer ( Scat ) to get the Stretch/Torque values, I guess now I have to ask them what kind of chit they are putting out and if they stand by their stuff. I planned on an Eagle rotating assy but I let my builder get it and he went with Scat. Anyone out there have any good experience with Scat?

[redhawk44]

Originally Posted by DSRE455

Crank needs to be redone, not every shop can do 3.25 main crankshafts. And that not going to last long at all

This is a 400 motor, so its 3 inch journals.

[Formulas]

Redhawk the pic of your rear main bearing what does the other half look like?

Can you feel the high low spots on your bearings or crankshaft if the crank caused them you should feel it on both if your bearings were faulty you would just feel it on the bearings

If you could watch the glint from a light off your crank surface while its turning you would be able to detect chatter the light would flicker off the crank surface instead of being steady

.

[redhawk44]

Thanks Formula, I'll check that out.

["QUICK-SILVER"]

I've seen what chatter marks on a crank does to bearings. It wears the bearing out, mills it away. Much like a crank that gets 'machine polished' in the wrong direction.

Crank chatter marks "favor" the defect bearing picture. Exception being the chatter mark lines run on a angle. They will be fairly evenly spaced but not perfectly straight, end to end, like the defect bearing picture.

"Ruffles have ridges"...And so did this bearing.


Clay

[hurryinhoosier62]

Originally Posted by "QUICK-SILVER"

I've seen what chatter marks on a crank does to bearings. It wears the bearing out, mills it away. Much like a crank that gets 'machine polished' in the wrong direction.

Crank chatter marks "favor" the defect bearing picture. Exception being the chatter mark lines run on a angle. They will be fairly evenly spaced but not perfectly straight, end to end, like the defect bearing picture.

"Ruffles have ridges"...And so did this bearing.


Clay

Clay, this is why I'm leaning toward there is taper in the journal as well as chatter marks.

[redhawk44]

Originally Posted by hurryinhoosier62

Clay, this is why I'm leaning toward there is taper in the journal as well as chatter marks.

So your saying its 2 problems? Taper in the journal and improper crank finishing.

[DSRE455]

Yeah needs the next undersize on the bearings, i use speed pro M series 3/4 groove mains, .002-.0025 main clearance, much fatter and hot idle oil pressure will be 15-20psi, fwiw

[redhawk44]

Originally Posted by DSRE455

Yeah needs the next undersize on the bearings, i use speed pro M series 3/4 groove mains, .002-.0025 main clearance, much fatter and hot idle oil pressure will be 15-20psi, fwiw

Is the chatter from the bearings not sized right? Loose in the journal?