Forged 6G72 TT crank, BETTER THAN NEW! $550 shipped to lower 48

[BaadVR4]

This crankshaft has been cryogenically treated and the main and rod journals nitride hardened to a depth of .015-.020". It has been blueprinted/indexed and checked to be straight. Rod and main journals are ground/polished. The factory nitride depth is only .002-.005", which means any turning of the shaft completely removes the hardening. By nitriding to .015-.020", there is enough hardened depth to allow another undercut without removing the hardening. Removing the hardening makes the crankshaft more likely to spin bearings. I am currently running this exact crankshaft in two fully built motors making over 600 AWHP and have over 6K street miles on each without any problems. $550 shipped to the lower 48. PM me for shipping to other areas. PayPal is milton_goldin@hotmail.com. If you have questions, you can call me on my cell at anytime. 478-335-6345.

[BaadVR4]

Weekend bump.

[1gRick]

Hi.....Sort of new to all this so bear with me. How exactly does lack of nitriding contrbute to spun bearing. Thanks for any and all help. Be safe.

[BaadVR4]

No problem at all. When the crankshaft journal surface and the bearing surface are close to the same hardness, it is easier for "galling" to occur under marginal lubrication and/or excessive heat conditions. Galling is a phenomenon where two metal surfaces with relative motion weld together, then tear apart. It is most common in press fit wrist pin/pistons, because the piston and pin move relative to each other, but have zero relative motion at both TDC and BDC.
Nitride hardening the journals reduces spun bearings by reducing galling and by making it more likely that small debris will imbed in the softer bearing material and not scratch the journal surface. Hope this helps.

Hi.....Sort of new to all this so bear with me. How exactly does lack of nitriding contrbute to spun bearing. Thanks for any and all help. Be safe.

[1gRick]

Hi...Thanks for a very insightfull and knowlegeable response, just what I was looking for. What do u think of the Clevite "coated beaings". Since u are so knowledgeabel I thought u might have accurate info on this issue.

[IPD]

No problem at all. When the crankshaft journal surface and the bearing surface are close to the same hardness, it is easier for "galling" to occur under marginal lubrication and/or excessive heat conditions. Galling is a phenomenon where two metal surfaces with relative motion weld together, then tear apart. It is most common in press fit wrist pin/pistons, because the piston and pin move relative to each other, but have zero relative motion at both TDC and BDC.
Nitride hardening the journals reduces spun bearings by reducing galling and by making it more likely that small debris will imbed in the softer bearing material and not scratch the journal surface. Hope this helps.

i didn't even know that. makes me super glad i did mine.

[BaadVR4]

I don't have any experience with them nor do I know anyone who has used them. The coating is a moly/graphite blend in a PTFE polymer base. So essentially it's a coating of moly assembly lube made into a Teflon type coating. The set up was originally designed for NASCAR racing. Clevite claims the coating helps prevent damage from cold starts and brief oil starvation situations. The coating thickness is only .0002-.0003" thick, so I would have to question how long it will last in street use. In a NASCAR situation the bearings only have to last 500 or so miles before they are replaced. In a street DD, they would have to last 30-40 times that mileage. The number of cold starts in a NASCAR engine is probably in the range of 5-10. Street engines would have to withstand as many as thousand times that many. It took me a good while to learn this lesson: not everything that works in a race car will work in a street car. I suspect this is one of those times. I think the coating will be gone sooner rather than later in a street driven car. I'm sure they will provide superior performance through the normal lifetime of bearings in a NASCAR engine, but after that they won't be much, if any better than non-coated bearings. Just my 1.5 cents worth.

Hi...Thanks for a very insightfull and knowlegeable response, just what I was looking for. What do u think of the Clevite "coated beaings". Since u are so knowledgeabel I thought u might have accurate info on this issue.

[IPD]

only last 20k miles for dd? really? i was hoping for at least 200k.

[1gRick]

Thank you for the info, sounds about right. Be safe.