Anyone found the main bearing housing bore .0015'' over the high spec on a factory iron 6.0L? Looks like GM is trying to **** with people on this, the factory bearings are larger OD than the new FM comp series bearings I have hear.

 

how tight are your mains now? spec is .0007-.0021 if I remember corect...

 

After the line hone(studs) we set the housing bore right in the middle of spec. Clearance is right at .0007''~.001'' with the GM bearings. With the FM's I get .002~.0022" I would like to be right at .0025''~.00275".

 

I stick to about.0023-.0025 on the mains if its iron. Did you also see that certain years of the 6.0 iron blocks they got funky with the cam bearings too? hhehehe. Thats a good one they did. I hope you are using a good pump with those tolerances.

Rick

 

Thanks for sharing your thoughts, I agree that over .0025'' would be getting loose. After checking out my old engine I have decided to set this one up the same. It was running right at .002'' with 5w~20 oil, and bearings still look perfect even after the blow up. I just have a stock 6.0L oil pump like the old engine. I have 3 sets of main bearings orderd so hopefully one will come in where I want. As for the cam bearings we will see shortly what kind of night mare Im getting into with those. Seems like every Gen 3 I have looked at new or old had copper showing on the cam bearings. I did a cam in a 6.0 that only had 2500 miles and had copper showing.

 

The copper on the cam bearings is normal with factory blocks. You will see it on one side more than the other. They actually hone the cam journals with the bearings in them for the final pass, so thats why you see the copper on every block. Its normal.

R

 

Im going to mark em, knock them out, clean the block ,and knock em back in I know it might sound crazy, but if they fit back in tight, it must be right

 

Locktite also.

R

 

why not just replace them?

 

Like he said earlier the factory installs the bearings, and line hones the cam tunnel with the bearings in. That's why you can have a new engine with copper showing on various spots the cam bearings. If you have a block with weird cam journals, and don't duplicate that possess you could be in trouble. The more copper, showing the more chance the cam tunnel is off. I have new bearings Im going to instal, and check, but if anything funny is going on the factory bearings are going back in.