964 case through-bolt o-rings

[john walker's workshop]

somewhere, maybe here, i once heard that some 964 engine cases were cut deeper in the area where the through-bolt o-rings live. never seen it, but now i have one that still leaks after new o-rings. enough to piss a guy off. anyone know about this? it's a '90.

[john walker's workshop]

i searched more and came up with this: Major oil leaking after fresh rebuild! Help!

but i see no listing anywhere, yet, for an optional through-bolt washer that goes deeper into the case. i have it apart again and this seems to be the issue.

[AlfonsoR]

I wish someone would get around to designing a better seal for these. In the mean time, I'll buy you a beer John....one of these days I'll make it up there. Sorry about your troubles there.

[porterdog]

I just did a little o-ring research (owning a '90 964 that will eventually need at least a re-seal if not a rebuild gives me a vested interest in seeing this issue solved).

theoringstore.com have a couple of interesting items. First is a broad selection of Viton o-ring cross sections. I'm thinking a thicker ring with the correct ID could be made to work.

Another is these Viton 'back-up rings'. While not metric, they may have a workable size. This would increase the height of the package some, and indeed one could use one inside and one outside the standard ring. I'd never seen these before, but like the idea.

Good luck, please keep us (me!) posted.

[AlfonsoR]

My 2006 Dodge has gaskets for the diff cocers that have soft rubber faces with small raised lips and sanwich a steel or SS metal core. The bolt holes have a thicker metal ring so that you don't sqeeze out the rubber. These gaskets are actually re-usable. I've done 2 oil changes and still no leaks.

Why couldn't someone design something similar for our engines?

[john walker's workshop]

if the cross-section was oval that would be better. they're 2mm round, so 3mm on the widest part of the oval would allow more crush. for now, i used two 0-rings on each side, a blue one on the inside and a green one on top of it. should be good now. chalk off 2 wasted days. oh well, it's a drop in a bucket of your lifetime. apparently there's a factory bulletin on this.

[Bill Verburg]

Originally Posted by john walker's workshop

if the cross-section was oval that would be better. they're 2mm round, so 3mm on the widest part of the oval would allow more crush. for now, i used two 0-rings on each side, a blue one on the inside and a green one on top of it. should be good now. chalk off 2 wasted days. oh well, it's a drop in a bucket of your lifetime. apparently there's a factory bulletin on this.

There is a TSB on that, if you need a copy let me know

[john walker's workshop]

love to have a copy. i have most of the white softcover factory technical bulletin books and i haven't found it yet. if it's in there, just the year and page # will do.

[Bill Verburg]

Originally Posted by john walker's workshop

love to have a copy. i have most of the white softcover factory technical bulletin books and i haven't found it yet. if it's in there, just the year and page # will do.

9107
dated 6/28/91

[Cupcar]

Book H, Technical Bulletins Jan - Dec 1991 page 29 affected engine numbers listed.

[IMG][/IMG]

[john walker's workshop]

thanks for the info. i have that book. back running with two o-rings and so far, no leaks.

[Cupcar]

I wish someone would answer my question on why did Porsche installed O rings on the lower though bolts #2,3,4,5 in the 993 RS crankcase and all racing and street crankcases going forward to the GT3?

They sit in a bevel between the case halves around the bolt.

Vibrations?

Anyway, I am doing it on the engine I am building now.