Cracked mains cap

Hi,
Just wondering why a main bearing cap would crack. Split in two starting or ending right next to the bolt hole.
Do you chamfer and polish the small radius next to these holes to avoid this, or should caps be replaced after a number of runs also?
Blown alky BAE engine putting out around 2500 HP.
No major damage done by the way, bearing shells and cranck still in perfect shape, just wondering why this happens to avoid it happening again.

Thanks,
Marcel

 

Thanks Will,

Just normal wear and tear so to speek. We'll be more carefull next time.

Anybody ever consider chamfering the sharp edges to avoid fatigue cracks in that area or doesn't that make any noticeable difference?

Thanks,
Marcel

 

I like steel main caps myself

 

broken main caps

To much timing trust me!

 

If you over torque the side bolt it will crack it right now . Some fuel guys won't take them full torque either--------

 

I have had this happen a few times now, on three different motors all BAE billets blocks, they all crack in the same place,always after 80-100 runs, if you look real close it starts right at a riser left from when they are machined, im not sure if that small sharpe edge creates a week point but it seems to be where the cracks always start, if you fit new caps just be sure to check that the seal track in the cap is concentric to the track in the block,I got caught the first time , we fitted the caps and line bored the block, put it together and she leaked everywhere, checked the next 2 and they also had to be machined so that the seal sat right

 

So you are talking about the rear main only ?

 

BAE mains cap updated design

We cracked cap #2 & 3. One straight through, the other just small cracks in the coating to show it was going as well. We had it examined by a metalurgist and it shows fatigue fractures from the sharp chamfer near the bolt hole. This is definitely a factor that attributes to the problem, but the fatigue fracture was only about 10% deep and the rest was a final rupture due to brute force. We now have a later design cap installed which does not have this sharp chamfer, but the brute force is still there, and we intend to keep the force active...
Talking to Jeremy and Andre at Brad I'm pretty sure they have recognised this to be a 'weak' spot after which it was modified. Please note I'm not saying it's weak, because forces involved are not exactly childs-play as well.
If in doubt give the guys at Brad a call and try to figure out if you have the old style or new style caps and decide for yourself if you should upgrade.