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http://www.350zfrenzy.com/forum/show...&threadid=5302
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Spun bearings are the restult of oil starvation, excessive high RPM operatation, or sustained detonation. This can happen to any motor...not just F/I. I am not certain of forged rods and upgraded rods bolts will help, but proper tuning will. Also, some folks will blueprint and balance the motor, and coat the bearings...which may help.

 

Looks to me like the PV for the bearings has been grossly exceeded - typical if going FI.

Bearing life was an issue on the Supra when tuned after that it was the Gearbox input shaft getting ripped off followed by Diff cases exploding.

If you significantly increase the power of your engine this is to be expected...

Cheers


Paul

 

What can we do to help prevent or avoid this type of failure?

 

my guess is don't do top speed racing like she does. She has lots of time at 145+ mph.

 

Wondering if that car had a crank pulley... ?

 

What would a pulley have to do with oil starvation?

 

It is not really an oil starvation problem. There are issues with changed crank harmonics when you change to the different pulley. This stresses the crank bearings which can lead to a failure (spun) bearing.

 

Well she has the SC so no Crank pulley change, so this point is non existant.

 

the guy also quoted he was running the car at 145...heating up the supercharger...not only that running the engine on a high load in such a high gear...puts alot of stress and work on the engine.....not the greatest idea to do on a FI car on a stock motor....

Ben

 

Well it is a gal, anyway, I guess that is the point if the engine is built up it doesn't address this area so if the engine is built up how will this be avoided?

 

ceramaic coating the main an rod bearings and running a very good synthetic oil (Redline, RP, Amsoil) are good precautions.

 

How will the ceramic coating on the bearings affect the clearances? Obviously make it tighter, but I mean should you order a smaller size and then coat it?

 

I have seen something like this before with main bearings. The one photo of the upper half of the bearing still in the block. You can see severe pitting in the surface of the bearing itself. This looks exactly like a set that came out of an engine that had a serious over fueling problem. The excess fuel actually corrodes the bearing surfaces and breaks down the oil film coating that normally protects them. I would lay money that this was the reason why the bearings spun...excess fuel in the oil. While the motor is apart have you're machinist look at the piston rings....they are probably sharpened to a razor edge from lack of oil protection on the cylinder walls. If this was what the problem was then that would explain the good oil pressure up to the moment of the failure...the oil was still there just not able to do it's job anymore.

 

Your machine shop/engine builder will fit the bearings to the rods. Inform them that you want them ceramic coating, and they will do the rest.

 

Thats a good point. Im going to have my oil tested by Blackstone after the motor build, even during the break in period, to watch what parts of the motor are wearing so to help avoid a total failure.

 

The Crankshaft pin diameter per litre on the VQ engine is one of the smallest in the world. The reason for this was to optimise inertial mass and reduce friction. This is however not good for significant power increases.

Anyone know if you can get wider bearings or even larger diameters with a new crank?

Supra engines could have wider big end bearings ground on them. This made a significant difference to engine life...



Paul

 

The AEBS stoker kit may be you're only hope for a new crank with different bearing specs...but I doubt they will be much different.

 

Was it a MAIN bearing failure or a ROD bearing failure?

A stroker crank will retain the stock main bearing diameter if I'm not mistaken.

Regarding the stroker, Popular Mechanics had a SUV shootout where they explained that the Pathfinder's engine is just a stroked 350Z engine (this month). It puts out much more torque of course.

I'm wondering if the Z's performance would benefit more from added torque vs added horsepower. This seems to be the path Nissan has chosen.

 

I did a nation wide search for a VQ40 crank during my engine build but couldnt find one. Just as well because i want to keep things as simple as possible.