rod bearing. Not sure how possible it is to spin a main bearing.

 

Just as easy.

 

Noticed that ceramic coatings are mentioned in the sig.

Just wondered if they changed the bearings to larger ones as the crank bearings are selectively fitted in .0002" increments, the Main bearings are fitted in .0001" increments.

This was done by Nissan to reduce vibration.

I am fairly sure that ceramic coatings are thicker than .0002" and could cause a transition or interference fit if the bearing sizes are not changed to cater for the coating.

Just my 02 (pence) worth!


Paul

 

IF the tolerances related to the bearing clearances are measured to 0.0001 verses .001 levels, it is easy for me to see why a bearing failure to happen. I was a journeyman guagemaker for 10 years in Detroit. I know anytime you have clearances defined in the "10,000th" range that they are extremely extremely small.

Are you sure we aren't talking about clearances measured to .001" ??

If the clearance is .0001 to .0002 it would seem (to me) that bearings would fail easily because there would be absolutely no room for the oil.

 

Are you saying that since she HAD ceramic coating already, perhaps it reduced the bearing to crank clearance....thereby reducing lubrication?

What should the bearing tolerances be in this area?

Should we be measuring them with plastigage?

 

Bearing selection is in 10ths of a thou so .0001" is correct not .001" I agree this is very tight.

If ceramic coating was applied it would reduce the clearance - i dont know what you could get away with.

I assume the engine bulider new this...

Cheers


Paul

 

The ceramic coatings are going in the new engine not the one that failed.

 

We need to find a good oil for these built FI engines. Im thinking Amsoil around 20 W50.

 

I have seen bad things with turbo's and synthetic oil. My dad had an 86 300zx turbo go bad and a second one in a 92 twin turbo 300zx....both on synthetic oils. Both bearing failures in lower mileage cars.

 

Did he break in the motor with synthetic? Which bearings failed? Man, will regular dyno oil withstand the heat?

 

after the breakin interval "all" good synth motor oils should outperform dino due to much more stable thernal stabilty both high and low temp. However; on a blown motor it is not recommended to take advantage of "extended" drain intervals. I use 5k miles just cuuse its easy to remember and 3.5k is just too pricey for me. I prefer either Amsoil, Redline or RP. At similar blends I would rate quality from least to best; however, they are all very very good synths. M1 rates just below Amsoil but is much cheaper per Qt. I am currently running Amsoil NA and prolly will run Redline 5w-30 after APS install.

 

These were cars with 30,000 and 40,000 miles that were switched over to synthetic from regular oil. Bearings that went were the turbo shaft bearings. He is not hard on his cars at all and lets them run for a couple minutes before shutting them off. Both were covered under warranty from the dealer.

 

Nissan does not recommend synthetic until after approx 10,000 miles with it's engines......interesting.