Date:         Mon, 13 Nov 95 11:15:03 PST
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         Dave Kautz <dkautz@hpsidms1.sid.hp.com>
Subject:      Re: 1700 Type IV head gaskets & Aluminum cars

  Wouter wrote:
> So I asked :
> 
> I want to pull the heads on a Type IV 1700 soon. As soon as I've clocked
> 10000 km (6000 mi for the metrically challenged :-). Just to have a look-see.
> So - do I need to replace those little aluminum or whatever seals between the
> top of the cylinder and the head? Or can I use Injun head on it? Or something
> else? 
> 
> and nobody replied. So I'm asking again :-)
> 
> (Heard in the wings, "persistant bugger, innit?" :-)
> 
> Do you guys have Land Rovers over there? Well, they're aluminum too. And
> isn't one of the new Audis also, or was that just a concept car I saw?
> 
> Wouter
> 
 
 Okay, okay. Most of the folks who fill their kitchens with type IV parts
 were out in Panamint Springs eating Al "Leatherlips" Knoll's outstanding
 chili and subsequently wishing that they had slipped a roll of toilet paper
 into the ice chest ........but that's another story.

 Anyway. I'd say replace the sealing rings. The seal is formed when this
 soft piece of metal is squeezed between two harder ones, conforming to
 the irregularities in the latter. It's kind of a "one shot" deal, unlike 
 a rubber seal which will "unconform" when unclamped. The metal seal MIGHT
 reform to a new shape, despite having been stretched and abused the first
 time, but it is so much work to get at those seals, why take a chance?



 On the topic of aluminum bodies - I thinks folks should make a clear 
 distinction between use of aluminum in stressed versus unstressed 
 applications. The Land-Rover <and other cars where a hood or a trunk is
 aluminum> uses aluminum body panels, but the vehicles structural strength
 comes from a robust, STEEL frame. Since most modern automobiles are built
 from formed sheets welded into a stress bearing structure, the fatigue
 characteristics of aluminum make it's use far more difficult. This is 
 addressed in aircraft by rigorous inspection, maintenance, and pre-emptive
 replacement. But even then, problems can occur, the Hawaiian Air 737 that
 developed a "sunroof" in mid-flight through which a flight attendant was
 sucked out as an example.

 The fatigue curve for steel mercifully flattens out so that old steel things
 can be counted on to have some high percentage of their original strength
 if corrosion hasn't taken it's toll. Aluminum, on the other hand, does not
 fatigue quickly but it does continue to do so in a pretty linear fashion,
 with strength dropping slowly over time. Failures usually appear as cracks
 in regions of highest stress.

 Now how about a bus body built from carbon fiber and epoxy???

 Dave