Sexy crack pics

[chancecasey]

Funny I didn't notice this until now, but there seems to be some signficant cracks on the upper part of the case, just below the blocky areas where the bolts go. (my 3.6L / 104K mi) Hopefully I'll have the case split within a month or so and I'll know more like if they are all the way through, just thought I'd see if anyone wanted to chime in with "my god, man! it's toast!" or if this isn't necessarily a terrible thing...


and some gratuitous extras because I'm so proud of myself having never done this before (let's not talk of putting it together just yet) look at that beautiful cross-hatching


a little head/cyl sealing problem on one cylinder, looks more dirty than any damage, but we'll see.



The crack thing is my biggest concern so far. Engine had great compression at PPI - could not do a leakdown. Seemed to have decent power, just leaked oil like CRAZY. All regular maintenance was done according to the stamps in the book. Hmm maybe I should part out the good stuff and buy taso's engine on ebay

[rcwaldo]

Looks as though those are just casting wrinkles where the aluminum cooled too quickly. You may want to sand them a little to expose what is below.

[sand_man]

Originally posted by rcwaldo
Looks as though those are just casting wrinkles where the aluminum cooled too quickly. You may want to sand them a little to expose what is below.

If I'm not mistaken, I think he's refering to the enourmous crack under the "casting wrinkles". I don't know enough to say one way or another if the case is toast...I would imagine it's bad, though.

EDIT: I just looked at the picture again and can't tell if that's a marker line or a crack???

[beepbeep]

Hard to say from that picture but it looks just like ordinary casting artefacts. I don't understand where those cracks would came from either.

[john walker's workshop]

i see no cracks.

[sammyg2]

My case is the same way. No worries.

[chancecasey]

Sorry, the pic isn't that good - and this was the best one! Flash was washing everything out. I've highlighted the cracks in red - everything else is just the natural features of the casting.

[sand_man]

When I first saw the picture, I thought you were talking about this (in red):

[chancecasey]

No, that's just a shadow. I took several angles and believe it or not this was the best shot. More difficult than it looks get the right shot in a dimly-lit garage - and more light was just washing everything out.

I'm all for sanding them to see if they're just superficial - any recommendations on grit and method?

[Henry Schmidt]

The leaking cylinders are caused by the heads bending. Your engine seems to have missed the factory recall on 964 head / cylinder sealing.
The proper repair is to replace the cylinders and cut the heads to fit later style cylinders.
If your pistons are still good, Supertec has new cylinders to fit your needs at very reasonable prices.
We are also carrying new Nikasil (not replated) cylinders in all 911 sizes at unbelievable low prices.
84, 86, 90, 92, 95, 98, 100, 102
Cheers

[sand_man]

Henry...email sent!

[Jeff Jagusch]

I'm not a die casting expert, but I believe what your photo shows are heat cracks that are in the tooling when the case was originally cast at the factory.
Die cast tooling life is reatively short lived, (say 150,000 castings).
I've heard it said that the best casting is the first out of a new tool, and the quality goes down from there. Heat cracks in the tooling are common place (at least in the industry we deal with, small air cooled engines).
Hope this helps?

Jeff

[Jeff Alton]

No cracks there. A lot of cases look just like that. My guess is that the "texture" that you see there has been there since that case came out of the casting process....

Cheers

[Jeff Alton]

Another option, only if your cylinders are in spec, is to have them machined by Rennsport Systems. Cost will be about 1/6 or less than the cost of *new* cylinders. They did a set for me that were great. They machine the tops of they cylinder to accept a 993 head gasket....

www.rennsportsystems.com

Just another option.....

cheers

[Henry Schmidt]

With all due respect ( I do respect Steve's expertise) the problem is not the cylinder. The problem is that the head itself bends due to poor support around the studs and a weak condition caused by the small fins cast into the head adjacent to the exhaust port and the addition of a porcelain insert in the exhaust port.
The only real fit is to use the late cylinders (quite often available in good used form) that affords the head support across a much greater surface.
While talking to Chance the other night he suggested machining the cylinder sealing surface off smooth so it resembled a late style cylinder.
Then you could put a base shim in to replace the material that was removed.
The idea has merit but it would take some engineering and someone willing to be a guinea pig.
Perhaps someone out there has tried this?
Another option is new Nikasil pistons to fit the Mahle cylinders you already have. SUPERTEC has them and the cost would be around $1,700.

[sand_man]

By the way, I'm by no means attempting to get your thread locked or myself banned, but I thought your "sexy crack" thread needed a little help:

Jeff

[chancecasey]

NICE!

[adomakin]

i have oak.

[BReyes]

right

[real550A]

thread needed a little help

That's a LOT of help!