Guys,

I had an engine blow on my 90GT, failed number 2 big end bearing,,, 6 was screwed as well when I opened up the engine. It blew while doing a sustained (45 mins) 150mph on an AutoB nr the Czech Republic. The conrod had exploded into half a dozen pieces and the block was not bad but I decided not to repair it at the moment.

Anyway, got a replacement GT engine with 70k on it for a song (picking it up this weekend), but before I put it in I want to check and modify the that crank journal so it won't happen again,,,, I know various firms do the work in the US but does anyone know what they actually do??

I can't find anyone in the UK that knows enough about it. It's a known issue when the engine is pushed but as parts are pretty easy to get here (meaning Europe) most people just replace the lump or crank and whatever has busted (which is what I was going to do and changed my mind).

Anyone going to spill the beans???

Regards.

 

I believe you can exchange your stock, undrilled crank for a drilled version at 928 Intl. for about $700.

The 2/6 journal is drilled to supply an alternate path for oil. The 2/6 journal is the first portion of the crank to see oil pressure from the pump and is therefore the first to fail when exposed to foam rather than oil.

You might also consider an Accusump.

Finally, the best solution is dry sump but you're talking big bucks.

Good luck.

 

"The fix was suggested by Taylor Machine and involves re-drilling the internal oiling passage and modifying a main bearing to feed oil in a different direction to the #2 and #6 rod bearing journal."

I got this quote by reading other posts on this subject and going to the 928 international site.

Does anyone actually know how this work is carried out? got any piccys?? I'm in the UK and sending a crank to the US to have it machined or exchanged is a process I'd like to aviod at this stage. I know I can it drilled in the UK if I know what to drill, what size, how to modify the bearing etc.

Cheers

 

Any competent "race" machine shop can "cross drill" your crank. It wont cost anywhere near $700.

 

Carlos,

When you say cross drill do you mean adding another two delivery holes to the 2 and 6 bearing journals. This is where I'm confused as normal cross drilling is where you drill through the existing single delivery hole at 180 degrees to it and produce a second hole. It's my understanding that all 928 cranks already have this (as mine had). Therefore,, like I mentioned above, are we talking about 4 holes per rod journal using the exisitng internal delivery channel???

And for anyone else reading this as well,,, what is this main bearing MOD??

Cheers buddy.

 

I've been told by several who have suffered the same loss, that after getting the crank re-drilled, they suffered the loss again. Basically, re-drilling does not solve the problem.

The best solution is a dry-sump. That gets complicated and expensive. As an alternative, an Accu-sump (if turned on) may be all you need.

Others have found that keeping the sump topped off and the revs below 6k will usually help avoid the problem. YMMV.

BTW, I've been there, and intimately know what it takes to rebuild a GT engine. :^( YMMV.

 

From what I know...the cross drilling and modifying the oil delivery path are two separate things.
Cross drilling has been reported to not be totally effective when just done by itself.

Changing the oil delivery to the 2/6 rod is effective from what I have heard. (Can't imagine how that would be done on a stock crank?)...anyone know?

There has also been a failure (not total) of the 2/6 on a car with the accusump.

It's all about money....dry sump is the best....Accusump good choice..keep revs below 6K..

And of course..while you are in there..just increase the stroke a bit.. ;-) and you get the modified oil delivery and cross drilling as part of the package...

later,
Tom
midlman@rennlist.com
89GT
87S4 AT for sale

 

Does anyone offer a dry sump?

Or is it totally DIY?

 

Hi,
soory to hear about your disaster, Two questions though;
A ) what brand & iscosity engine oil were you on and?
B ) did the engine use much oil?
Regards

 

Isn't this the problem and remedy mentioned at 928 Internationals site as Nobby mentioned? (see link)

<a href="http://www.928intl.com/tips/artcl_03.html" target="_blank">http://www.928intl.com/tips/artcl_03.html</a>

 

Simply stated the drilling is NOT just cross drilling but drilling to feed oil from a different direction and different main bearing (which must be grooved)to the #2,6 rod journal . Basically it is drilled "like a chevy " crank . As mentioned the stroker cranks made by Scat who make millions of chevy cranks are "drilled like a chevy" . Taylor Machine in Whittier Ca drills our cranks . Scat makes our stroker cranks .

 

Jim might nbe the guy to expand on this...
but didn't Mark try dry-sumping ...with what?
A five gallon reservior and still lost a crank?
Since Jim/928INT'L sell the cross-drilled cranks maybe he could enlighten us, though from my limited understanding this is only a concern of high-speed long distance runners, hard charging Pony Express types, and those who seek real pain on a track, G-force, oil starvation at high rpm usually a curve involved.
Since the rest of the 928 community is composed of, law abiding, conservative, Sunday drivers we need not be concerned.

 

The thing that bugs me here is this happend in what appears to be a "straight line", meaning no sustained turns etc etc. He was just cruising along on an autobahn and KABOOM! That isnt good!

Sounds like its oil level related to me.

<img border="0" alt="[cheers]" title="" src="graemlins/beerchug.gif" />

 

A GT at 150 mph should be about 5,500 RPM, and that was for a sustained 45 minutes or so. It may have been straight line and no turns when the failure occured, but it's also possible that some or much of the damage was done previously too.

 

Sorry to hear about your lost. As we all ponder this subject while you search for answers…can you give us a little bit more history on your car and the conditions this happened under.

Straight line cruising…no hard corners…fresh oil? Topped off? Did your shark use any oil prior to this?

This kind of information can set the stage possible for a problem that may need further addressing from the 928 Gods above…maybe we don’t have the dreaded 2/6 failure figured out completely yet.

I’ve been considering DE events this summer and if the 2/6 is reappearing as possible not being totally solved…maybe I’ll reconsider that…don’t need those headaches. You’d think Porsche would have had a handle on something as simple as this.

So...does this mean my shark can't handle high speeds in a straight line for 45 minutes???

<img border="0" alt="[typing]" title="" src="graemlins/yltype.gif" />