I am ready to disassemble and after machine shop put my 96 LT1 together for installation. I have read several posts on here that discuss or mention death by spun bearing. I don't see this associated with other SMBlock Chevy engines.
What is the cause and is there anything preventative other than assembly tolerances and torque?
I don't want to do what I have read and put it together and have it go boom before I have time to enjoy the work and $.

 

Higher quality bearings pretty much fix the situation.

 

Good oil pressure is recommended.

 

"Spun bearing" are not a primary failure mode. They may occur in any engine. The reason is lack of oil at the crank/bearing interface. This can be exacerbated by clearances that are too tight or too much flex in the crank, etc. When the clearances are already tight and if there is excessive flex, especially if the oil film is marginal, you get metal to metal contact. This typically leads to a "wiped" bearing, not a "spun" bearing. But if it is severe enough, the bearing can spin.

The commonest reason for an LT1 to spin a bearing is a HV pump with a stock pan. Combined with high rpm, high G-forces, and maybe a marginal oil level, there is a distinct possibility of oil starvation and spun bearings. For some reason, the idea that a HV oil pump is needed/desirable has become curent in the 4th gen world. With a typical LT1, there is absolutelt NOTHING to gain from an HV pump. It takes more power to drive than a stock volume pump, and the risk is as described above. IF you have an aftermarket pan with better oil control and larger capacity, the HV pump should not cause a problem, though it will still gain nothing and actually cost a few hp. The only time you need an HV pump is for a very hi-po motor set up with clearances on the loose side. Or, if you run at very high rpm (8,000up) it may also help because it is less likely to cavitate at very high flow rates.

All in all, the best pump for an LT1 is a stock volume pump with a high pressure spring. It is worth noting that no less than John Lingenfelter, one of the gods of the SBC, recommended and used STOCK oil pumps (with HP springs) on his street/street strip SBC motors.

Rich

 

If you do it right, you shouldn't experience any problems, however, it takes a nano-second to ruin an engine if no oil pressure and damage of the cam or bearings due to sloppy install, including install exposure to dirt and debris. JMHO

 

I was interested/concerned about this same topic. I did research on this board, and the two main reasons I found for spun bearings included a sloppy install (including getting dirt in there), and spinning the engine too high (relative to the quality of the parts).

 

Hey Rich do you recommed the HP spring on a heads/cam car ~400rwhp? or should I just stay stock? If not where can I get this spring and is it difficult to intstall?

 

The white spring is GM part 3848911 and I would put it in any engine. You have to remove the bottom plate on the pump and drive out a pin to access the spring. Easy (as long as the pump is out ).

 

Agree with Mr. Shoebox. I always use 'em.

Rich

 

Thank you all for the information. Probably the best info is that on the HV pumps. I had been considering their use but after reading this it is best to stay with what worked "back in the day" which was higher pressure. I have only put a couple of engines together back when the 327/365 was the hot ticket and it and a 350 survived in the rpm range where none should go without a scatter shield but by the grace of God the clutches stayed together.
I will just have to get the assembly completed before the Texas dust season arrives or catch a rainy day....yeah right on the rain.

 

The white spring increases the pressure just enough to help the engine live a more healthy life. It's not going to overwhelm the engine with oil pressure. You'll see around 70 psi, cold with normal bearing clearances.