Head gasket is wrong type of engineering?

[rverdoold]

Ok to explain my question further than in the title. Current head gaskets are engineered as such that you require a flat cylinder block top and a flat head surface. Both are connected using ~3 bolts per cylinder and a piece of flat material in between.

I work a lot with ultra high vacuum systems (<10-9 Bar) also here gaskets are extremely important. However the big difference is the pressure. Vacuum is negative, engine cylinders are positive. However sealing remains the main similarity.

In the vacuum system the copper gasket (usually ring shaped) has two flat surfaces, however the two connecting parts (lets say cylinder top and head) have a circle cut out in which the copper ring fits. But there is an extra edge which fits in the middle of the copper ring it is usually rather sharp which actually cuts into the copper (so called ConFlat http://upload.wikimedia.org/wikipedia/commons/6/61/Conflat_Flange.jpg. )

 

Would this type of engineering be suitable for engine manufacturing? However it would drastically change the design of a head gasket.

[WoodsWagon]

Sounds like the same thing that's accomplished by "o-ringing" a cylinder head. Basically a groove is cut into the cylinder head and a ring of piano wire is put in that crushes the headgasket in a ring around the cylinder. It's used in high-boost applications where the cylinder pressures are high enough to blow the headgasket out.

[idosubaru]

there's no need and it's not cost effective.

 

alternate ways of sealing have been around for a long time. for that matter, alternate ways of doing lots of things are available but not used - it's simply not cost effective.

 

it's not a "wrong type of engineering". it is incorrect to assume that Subaru's goal is to produce an engine that never has headgasket issues - that isn't even close to reality. they are okay with some risk to that end.

 

if they were that concerned about it they would have far more focus on headgaskets than they have. they're okay with a slight amount of risk and quite possibly the repair/maintenance/parts market is getting a good boost so there's a cost/reward curve in play too - it's not as black and white as one might think. they're okay with loosing some customers if the rest of the Subaru community is paying higher repair and parts costs.

 

manufacturers don't make money selling new cars any more, that statistic swung hard and fast in the 80's and 90's. now they might rather have more cars generating maintenance/repair costs than producing lower maintenance vehicles - repairs costs are where most dealers are making their profits (that and used cars). consumers are uneducated, most *think* they're educated so that just compounds that dynamic!! so rather than thinking of new cars as some pinnacle product that generates revenue....it might be accurate to also include the idea that new cars are an infusion of revenue generation into the consumer world.

 

manufacturers are okay with certain risks in exchange for other things. what seems simple on the surface has financial costs, opportunity costs, or other costs associated with it in the real world. one can sit back and arm chair design anything - manufacturers live in the real world of costs, economies, exchange rates, marketing, competition, 20 year strategies, and fickle uneducated consumers. their world and ours have completely different modes of operation.

[WoodsWagon]

Dealerships certainly don't make their money on new car sales vs service anymore, but manufacturers are completely separate from the dealers. The manufacturer is still making it's money on the selling of new cars, not parts. That's why you get stuffing of the dealership's inventory, the manufacturer wants the cars on the dealership's floor plan financing to keep their bottom line going.

 

I don't think cars are engineered to be service work generators. If they were, they'd be a lot easier to fit your hands and tools into and a lot less reliable. You can neglect the hell out of a modern car and it will give you 150k miles of service. Try that with a 70's car.

 

There is planned obsolescence engineered in of course and cost saving measures, but they are not for the benefit of dealership service departments.

Saying Subaru manufactures shoddy headgaskets to feed work to their dealerships is false.

[GeneralDisorder]

I've been involved with some block o-ringing applications and was also a vacuum pump technician in a former career - though I only occasionally dealt with ultra-high vac.... most of the stuff I did was in the 10 micron or lower range - but very high volume. Freeze drying pumps for example.

 

O-ringing is VERY similar to the ConFlat style flange.

 

The biggest difference between vacuum and an internal combustion engine is the temperature variations. A head gasket must seal while the block and head are allowed to expand and contract at different rates - thus allowing a miniscule amount of movement. The ConFlat flange setup and other high-vac type systems do not allow for ANY relative movement between the sealing surfaces.

 

It comes down to cost. You could simply machine the head and block to a laboratory quality, flat, mirrored finish. And then use nothing between them. Some engines used in top-fuel drag racing are built this way. Running nitro-methane and putting out in excess of 10,000 HP. Extremely tight tollerances and no gasket..... nothing to blow out.... well except when something *does* go wrong they catastrophically detonate.

 

In the end a gasket is much cheaper than o-ringing, and other options. Could they do o-rings from the facory? Sure. But they don't *have* to do it to get the results they need. Thus the added cost for insurance against what amounts to a tiny percentage of failures in the thousands of cars built isn't worth it.

 

GD

Edited May 6, 2012 by GeneralDisorder

[idosubaru]

Saying Subaru manufactures shoddy headgaskets to feed work to their dealerships is false.

right on miles, i'm with you. i totally agree, i never meant to suggest it was intentional. But the QC/TQM (Quality Control) Industrial Engineering principles outlined to Japanese companies for post World War II rebuilding that has made them the successful ventures they are today (read about Edward Demming, it's a fascinating story that everyone should know)....aren't being followed or there wouldn't be a 15 year headgasket issue with half-hearted, ill-fated attempts to alleviate them.

 

to that end - as i mentioned before - Subaru is okay with risk, not that they are intentionally doing it. interpret that however you wish, i may make some half-hearted tongue in cheek suggestions (using the phrase "it might be more accurate to include"...which are very ambiguous words and not a statement of fact) that are silly, but they are okay with the risk for some financial reason.

 

i wasn't referring to DIY folks, we're a blip on the radar screen - an anomaly. so "ease" of work hardly plays into it. has more to do with disposability in our culture....

 

but nonetheless the original question has a simple answer - it's not cost effective, there's simply no reason or need.

Edited May 7, 2012 by grossgary

[ivans imports]

it all has to do with the expanison of the heads against the block as they heat up and cool down they expand and contract untill the gasket works loose they have had the same problem since the ea 71 headgasket have always been working loose on subaru moters since day one i think oringing whould still suffer from same efects cement the block mabee

[rverdoold]

Interesting opinions and knowledge, Thank you.

Heating and cooling is not a direct problem if you choose the right material. I also bake the vacuum system at couple hundred degrees (F).