scratched case half. How bad?
 

Hi everyone,

Rebuilding my 1989 911 3.2 with 212K miles on it and no top end or case work ever. Yesterday, removed case half set aside, and was done for the day. left the oil pump in for today. I don't have any 911 engine rebuilding experience, except that I replaced my timing chains (successfully) about 4 years ago.

Problem statement: When I was bending one of the tabs on the nuts for the oil pump, my screwdriver slipped, and scratched the case half. I'm nut sure how deep, but I'd have to think it's a couple thousandths of an inch?

The start of the scratch is pretty close to the grunge line, which I assume is the edge of the inside of the case?

Would appreciate some advice on whether this is a small, medium or large problem. For what it's worth, it seems like there are other scratches, very straight, and parallel to the case half edge, but not by me.

Pic Below.

Thanks in advance for any thoughts or advice,

Mark

http://forums.pelicanparts.com/uploa...1531696177.jpg

Scrap the cases, they’re unsalvageable.

Just kidding, just make sure you get the area nicely covered with Threebond or Loctite 574 during reassembly.

That will cause a leak. Sand it down.

Yamabond, threebond, is the answer but follow the directions and apply to both R and L flanges as instructions dictate.
Bruce

So to fix this, sanding down making a deeper depression will prevent the leak?

I don't follow this logic? :confused:

I just used Threebond and am super impressed with it. It'll fill that minor void no problem, unless I am not seeing the scratch posted? :confused:

The scratch is the one directly left of the stud that ends up in the lhole. Again, was from a screwdriver that slipped when bending back one of the tabs on the oil pump nut. The stud in the picture is the actual pump stud. I can try to figure out by looking at the case halves whether this is a location where oil could get from "inside" to "outside".

Thx

I would block sand if any raised metal areas. Clean well. Then use a credit card or the like to fill gouge with JB weld. Re-block sand after 12 hours and carry on.....

You sand the scratch to make sure you are knocking down any raised areas that were created by the screwdriver, not to expand any low areas. The screwdriver will make a microscopic trench that will have high points that are higher than the old case mating surface.

I don’t have the calculations in front of me, but the clamping force of the perimeter bolts and through bolts would easily push the high metal down IMO.

as Tippy said ..do not worry too much clean the area, apply 574 in my case i only would put it on one half of the case .The reason is if you do not know how much to apply it is possible you would use too much and that would not be goood;-)
Here is how i do it...
https://www.youtube.com/watch?v=IandhtwG5no

Ivan

My case was pretty hacked from a previous owner's rebuild. I used an Arkansas stone to smooth it out and sealed the outer half with Yamabond (loctite 574 for the bearing saddle surfaces). Motor has 1500 miles and is leak free.

MSC sells the stones- coarse on one side/ fine on the other
https://www.mscdirect.com/browse/tnpla/00580381?cid=ppc-google-New+-+Abrasives+-+PLA_sNxHmM8jb___164110813434_c_S&mkwid=sNxHmM8jb| dc&pcrid=164110813434&rd=k&product_id=00580381&gcl id=EAIaIQobChMInt3a5Nam3AIVFLjACh3k4AM4EAQYASABEgJ BxvD_BwE

deburring and smoothing the case halves is called good engine building practice ;)

I went over my case halfs with a piece of flat fine sharpening stone wetted with 3in1 oil. Iy nicely deburrs and leaves the surface silky smooth. This is what you want to do to the area with the scratch. The loctite sealant fills in all but the deepest scratches.

That scratch looks pretty shallow.. I wouldn't worry much.. when you go to clean everything and scrape gently with a blade, (holding it perpendicular to the surface), clean it all, and then use the three bond.. it will all be fine.