I have owned an F body for almost two years now and in my research I have noticed that there are people spinning bearings after doing a cam or head swap. These cases seem to be restricted to high mileage LT1 cars.I have also read articles in puplications recommending against breaking into a high mileage long block for the very reason of the possibility of spinning a bearing.What I have not seen discussed is why this is occurring . I have built and modified several engines(non LT1) over the years and never did I spin a bearing.I will tell you right now that I am not an engineer but I do have some thoughts and opinions that I would like to share and maybe get some of yours.First of all I will tell you a little about my experience with LT1 cylinder heads. I purchased a 94 Z in March of 2003. I had heard a lot about these cars before I bought one and was impressed with the performance . I bought it knowing about issues that needed atttention. Mainly broken exhaust manifold bolts.(Another problem area - apparantly these sometimes break on there own due to manifold design and heat cycling). Anyway I had heard of these bearing issues before I pulled these heads off (both sides) to remove broken bolts and have some other items tended to. My theory is that these engines seem to take a set after a lot of miles and I was very meticulus about head bolt removal. All these bolts when torqued to specs are bound to move something around and when bearing clearances are measured in thousandths of an inch it is not going to take much of a change in proximity to cause a problem. So when I removed the heads , both sides, I was very careful to remove them in the exact opposite order of assembly and not randomly rip out bolts.I started by just breaking them loose (in sequence and side to side) and then backing off one turn for each bolt until loose. It took a while but I was surprised how tight the first bolt was when I got back around to it. I gave the machine shop specific instructions NOT to mill the heads unless absolutley necessary. I also made it a note not to turn the engine once I got the heads off and made sure that the block deck was spotless before the heads went on. Reassembly was again done in sequence and side to side to evenly load the block as the bolts were torqued into place(20 POUND INCREMENTS).After I finished the project I was really concerned about all those horror stories of spun bearings but it has been about seven months since the work was done and have not had any issues. Any other theories about this subject?

 

The GM High Tech article was discussed extensively here when it was published:

http://web.camaross.com/forums/showt...t=spun+bearing

 

Been a pretty hot topic from time to time in LT1 Tech also. Here's a link to one of the most recent threads.

http://web.camaross.com/forums/showt...=spun+bearings

-Mindgame

 

Interesting reading,Thanks for pointing me there .Still a lot of different ideas . It would be nice if someone could do a failure analysis and get a definitive annswer.

 

This site has some good pics. of failed bearings and their causes.

http://www.engineparts.com/motorhead...gfailures.htm#