Will detination cause the top areas of bearings to shave away?

Im rebuilding my engine for the 2nd time. I told my engine builder to examine the damage very carefully to determine the cause.

He noticed that the top parts of the bearings are down to the brass while the bottoms are still intact with little to no damage.

Will detination (inproper tune, no nitrous use) cause this?

Let's define "tops" and "bottoms"

Tops = the bearing half that is in the block, usually grooved.

Bottoms = the bearing half that is in the main caps, usually without a groove.

Only time I have seen the TOP half of the bearing get chewed up was with a blower- the tension of the drive belt pulls up on the snout of the crank and causes excessive wear on the top half of the front-most bearing. Other than that, no real problems with the tops.

Bottom bearing halves can definitely get "hammered" by detonation, though.

Detonation causes a violent downward push on the rods and the crank- it tries to push it out the bottom of the motor. Hence, the bottom halves of the bearings take the worst damage, at least initially. Once it gets bad everythying can go to heck in a handbasket.

If you are talking rod bearings then yes the top half will get the hammering.
YES

If it just started it will look like spots on the bearing simular to a water drop droped into water except tiny little spots.(circles)
If your top half is down to the copper then I would suggest a better quality bearing like Clevitte CB663H for the rods and MS909H for the mains. Ya might want to replace the cam brgs too they are SH1349S.
Ya also may want to beef up your oiling with a better pump like a 3/4" HV and a pan.

I had something similar happen to me with rod bearings(only on the uppers) in a 3rd gen car is had. The machine shop I talked to and showed the bearings to believed it was the result of running too much timing advance. I did not have any detonation, but I WAS running it with more timing advance normal and I did not tell the guy this before he made his diagnosis.

thanks for the insight guys.. I really dont want this to happen again...

I think the tune brian from pcmforless is good.. but on the 2nd new engine i ran a messed up tune for 50 miles.....

thanks for the insight guys.. I really dont want this to happen again...

I think the tune brian from pcmforless is good.. but on the 2nd new engine i ran a messed up tune for 50 miles.....

That may have got it started working on the bearings. If the brgs were "soft" then it kept on eating the brgs.
Make sure ya got the brgs I listed above or the equivelant 'cause they can take more abuse. It could have been a clearance or oiling problem also.
To tight and ya don't have the oil cushion to take a pounding.To thin of an oil too. Lack of oil just for the bat of an eye would have started it too.
Not saying ya had any of this,just food for thought.

Clevite's "Bearing Failure Analysis" paper is a very good read.

http://engineparts.com/publications/CL77-3-402.pdf

-Mindgame