Re-nitriding the crank, grinding

[Supra]

What are the acceptable limits for grinding a crank for an engine running 500-600RWHP?

How much removal warrents re-nitridng the crank & where can you get this done? (midwest prefered)

 

[malloynx]

the stock 7m crank is very strong. i had .010 removed from mine and i'm running over 500rwhp daily. all is well

 

[aljordan]

I would search out a good crank that doesn't need to be machined. The most I'd want to do to a crank would be to polish it.

That way one can still use the toyota bearing sizes.

 

[IJ.]

The stock hardening is only 10>15 thou deep but I guess this varies crank to crank so first US is safe anything else and it's either get it retreated or find a good crank as Al has noted.

 

[Adjuster]

Another option is hard chrome.

Check out Crankshaftspecialist.com

Nice guys in Nashville, TN. They hard chromed my journals when the stroker crank they built me "twisted" under extreme detonation caused by the dumbass shop mechanic that did not hook up my AFPR to a vac source, and did not hook up my boost controller's MAP sensor. (So, controller see's no signal to control boost, and the fuel pressure is not raised up along with boost, and then he takes car out and whips it.... Can we say lean detonation folks...)

Great thing about hard chromed journals is the material is very strong, yet so hard it would be brittle if the entire crank was made from it. The crank is forged from slightly flexable iron, so it allows some movement to dampen dynamic forces as the engine is running, yet the super hard chrome journals are there at the wear surfaces where you need the hard surface. (Problem is cost, figure about 750 or more for a full crank. Mine was cheaper since they were not sure if the crank twisted as a result of the stroke being added due to welding, or some problem on my end. Cost was about 480.00..... and I ended up paying that, and more as the shop never admitted to the error, even though they fired the mechanic over this and other stuff he was doing.)

 

[gixxer750]

You don't want .020. My last crank was, and I had some scuffing on the journals, but the bearings where still ok on most cylinders.

 

[Supra]

Just an update since I forgot that I started this thread. )

I ended up buying a new Toyota 7M crank. It arrived today. I opted for the 7m over the 6m because I feel it will yield a smoother feeling motor and because it cost less than the 6m crank. The weight differance seems to be 57lbs (7m) verses 52lbs (6m). The power loss from that is negligable in a daily driver.

 

[Nick M]

I don't think you can buy an older 7M( 7MGE-7MGTE) crankshaft with a new part number. That is usually how upgrades go. The old part is dropped for a better one.

Perhaps a bigger dealer has the old ones new if somebody wanted one.

 

[supra90turbo]

mmmm.... someone get me a deal on a brand-spankin-new Toyota 7M crank!

 

[IJ.]

mmmm.... someone get me a deal on a brand-spankin-new Toyota 7M crank!

I have a perfect fully prepped 6M crank here ready to go but shipping would kill any savings I could offer Kurt!

 

[Supra]

I don't think you can buy an older 7M( 7MGE-7MGTE) crankshaft with a new part number. That is usually how upgrades go. The old part is dropped for a better one.

Perhaps a bigger dealer has the old ones new if somebody wanted one.

If you mean I can't buy a 6M crank verses a 7M crank - they offered me the 7M crank or the 6M crank. Price differance was ~$40 cheaper on the 7M crank. 7M = cheaper FYI. According to Champion Toyota, my 7M crank was the last one left in the USA - you now have to wait 6-8 weeks for a 7M crank via boat. 6M crank is supposed to be available.

I think I posted this elsewhere but the 7M crank's extra counter wieghts on the second journal hit the block near the oil pump (I assume this is due to using an early 7M block that had a 6M crank). You will have to grind the block a bit for clearance.