crack in crankcase opinions appreciated

[bb3188]

Hi Guys,

Great forum with a lot of interesting post !

Just picked up a 78 911sc and was going through it over the hoist for the first time today and noticed a crack of on the bottom of the crankcase.
I have search through the forum and some cracks appear to be superfical (from the casting process) while others require repair.
I would like your thoughts on the pictures below
(a) is it just casting cracks or
(b) or a real crack....and if so, what are my options?

I should add that oil does not leak from the crack..........
thank you in advance for your help !!

Mark

[bb3188]

here is another pic, in detail

thanks !

[Flat6pac]

If it doesnt leak, I would think it is superficial. I have seen lines on other cases and they look like casting flaws. If the case had been hit there would be a chunk out as if you had lost a rod.
Bruce

[cgarr]

That almost looks like an old repair, maybe it has been welded before? Pull the oil plate a take a peek inside and see if it lost a rod at one time.

[bb3188]

Originally Posted by cgarr

That almost looks like an old repair, maybe it has been welded before? Pull the oil plate a take a peek inside and see if it lost a rod at one time.

yeah, I will do that ...worth a look.

should i then leave it ie will it hold as it is ? or look to get this rewelded ??

rgd

Mark

[bb3188]

hi guys, did a compression test tis afternoon,
the range was between 142.5 to 152 with most of the other cylinders around 145 psi..........
it was done cold which is a good sign I think .............

once everyone back to work, i will try to organise a leakdown test.......... fingers crossed !

[burgermeister]

Sometimes aluminum castings have areas that look just like cracks, but aren't. You can try light sanding & polishing of the area - if the crack goes away, it wasn't a crack.

[bb3188]

Originally Posted by burgermeister

Sometimes aluminum castings have areas that look just like cracks, but aren't. You can try light sanding & polishing of the area - if the crack goes away, it wasn't a crack.

Burgermeister, I might give that a shot today to see how that goes...I so wish that its only a casting mark....(fingers and toes crossed)!

[RarlyL8]

I'd say those are just superficial lines on the surface and not cracks. I've seen lines like that before and not noticed any issues. It does look like a repair of sorts but what I don't know.