spining bearings..

Marvin97 · Jan 2, 2009

Ok, so i've looked at doing my pi swap for a while now, I have some ported and polished pi heads, intake, ac delete and whatnot. What I've found though, is that alot of modulars experience what people are calling "spinning bearings" or "spun a bearing". What are they talking about? I plan on my car making upwards of 400rwhp from a twinscrew later this year, and I want to do what i need to do to prevent this. But I don't know what they're talking about. Please help, pics would be great, thanks!

Marvin

MustangChris · Jan 2, 2009

97whitevert said:
Ok, so i've looked at doing my pi swap for a while now, I have some ported and polished pi heads, intake, ac delete and whatnot. What I've found though, is that alot of modulars experience what people are calling "spinning bearings" or "spun a bearing". What are they talking about? I plan on my car making upwards of 400rwhp from a twinscrew later this year, and I want to do what i need to do to prevent this. But I don't know what they're talking about. Please help, pics would be great, thanks!

Marvin

believe they are talking about blowing the main bearings on the crankshaft. Remember our lower end can only handle 425 crank HP stock. I suggest something lower than that to be safe. When in doubt, buy a crankshaft! :-D lol

BigTang · Jan 2, 2009

spun bearings are typically caused by 2 things. RPM and lack of proper oiling. Talk to your engine builder about the tolerances that your engine needs to have and make sure you use at the very least a new oil pump, if not an upgraded one.
a spun bearing is when the rotating part, in this case the crankshaft, contacts the bearing(remember it rides on a slight cushion of oil) and grabs a hold of the bearing and twists it in its seat trashing the crank and causing you to need a line bore on the mains in the block. The cams actually don't use any bearings on the 4.6's and rely on the bore in the head itself as its bearing surface, if you screw up that surface you have to get it line bored and have bearings installed.