Always a good idea to Magnaflux the block.......

[bison]

How do you think rotating assembly balance (bob weight) affects cap walk? I'm not 100% on what the different balance percentages do, but doesn't one limit affect horizontal vibration and the other vertical?

They don't effect it.

 

[TurboDave]

Speaking of main studs.... If a person were to remove the bolts and replace them with studs, does this require any other work? Do the mains need to be honed? Will clearances change if nothing else is done?

 

[turbodave231]

How do you think rotating assembly balance (bob weight) affects cap walk? I'm not 100% on what the different balance percentages do, but doesn't one limit affect horizontal vibration and the other vertical?

Imbalance will put additional loads on the mains.....that is obvious. So balancing the rotating assembly is important. I never thought much about how the difference in balance factors might affect main cap or block life.

From what I've read and observed about balancing, the 90 degree v6 has a natural imbalance that can never be eliminated. The Buick V6's 36.6% balance factor put the primary couple in the horizontal plane (the crank wants to move side to side). Buick did this so they could absorb (cover up) the unwanted vibrations with engine mounts. The 50% BF moves the couple into the vertical plane (crank wants to move up and down) Seems to me that with weaker stock main caps and main bearing webs, this would be more detrimental than the 36.6% BF.

For what its worth, I have balanced lots of engines both ways 36.6 and 50%. I can't really tell the difference!! Brian is probably right. The different Balance Factors probably don't matter for the life of the mains........but an unbalanced engine.......that is something completely different. I think anybody who builds one of these engines and doesn't balance the assembly is a bit foolish.

I have measured Buick V6 mains with bolts and then switched to studs and remeasured. (I'm using precision bore gauges that read to .0001"). I could not measure any additional out of round with the studs. But my sample size is not statistically valid. If you are going to use studs, install the studs and then measure. If the mains don't meet the spec, align hone.

 

[larrym]

very interesting thread lots of experience to draw from with this crowd. I never even thought about the bottoming tap on main studs.

 

[TurboDave]

I have measured Buick V6 mains with bolts and then switched to studs and remeasured. (I'm using precision bore gauges that read to .0001"). I could not measure any additional out of round with the studs. But my sample size is not statistically valid. If you are going to use studs, install the studs and then measure. If the mains don't meet the spec, align hone.

I was hoping you had a larger statistical size. My short block is already assembled (with bolts). I'd hate to tear it down just to measure with studs. Guess I'll leave it. (my bore gauges only read to .0005).