Head gasket, Is this the VW bulletin? Options

[DavidSweden]

I am currently rebuilding engine. In order not to tire everyone with a lot of newbie questions I have been searching the forum (thanks for the tip Cap´n).

There has been a lot of debate about using or not using head gaskets. Is this the VW tech bulletin which has been referred to in some of the post recommending not to use the head gaskets? VW Tech bulletin head gasket

David

[ClayPerrine]

Just a point I would like to make.....


Betty is driving a 914-4 that has 365,000 miles. During that time the engine has always had the head gaskets installed. And it has NEVER experienced a head sealing issue, EVER. The engine has been rebuilt 3 times since she has owned it. The first one at 150,000 miles.

There is nothing in any Porsche manual or bulletin that says not to use them. And I have had excellent results using them.

Look at it this way....


If you use the head gasket, and there is a leak between the head and the jug, you burn a slot in the gasket. You take it off and throw it away.

If you don't use a head gasket, and there is a leak between the head and the jug, you will end up burning a slot in the head or the jug. Repairs to the head will be expensive. The jug will have to be replaced, and that is expensive too.

I consider that cheap insurance.

[DBCooper]

There is nothing in any Porsche manual or bulletin that says not to use them.

(IMG:style_emoticons/default/dead horse.gif) True, but why is the "Porsche" part even relevant? It's a VW engine in your car and a VW tech bulletin. Is it really prudent to ignore their advice? Their advice about their own engine?

If you use the head gasket, and there is a leak between the head and the jug, you burn a slot in the gasket. You take it off and throw it away.

If you don't use a head gasket, and there is a leak between the head and the jug, you will end up burning a slot in the head or the jug. Repairs to the head will be expensive. The jug will have to be replaced, and that is expensive too.

Unfortunately that's not how it works. I've never heard of a gasket failing without damaging the head, unless it was caught in time purely by chance. The material in the crushable head gasket is softer than the aluminum head or the iron cylinders so the flame will indeed burn a slot in the gasket first. But that hot spot in the gasket enlarges every time hot compression gasses get squirted through it, eroding the metal. The slot never gets a chance to cool so very quickly (no shit quickly) it burns a channel into the aluminum head. That's the "blowtorch effect" that's been mentioned. An aircooled engine makes a lot of noise, so unless you know what you're listening for you won't hear it until it's already bad enough to have trenched your head past where it can be fixed with a fly-cut. Once started it can do that damage in one good stretch on the freeway.

For good order's sake it is entirely possible that the same thing could occur if no gasket is used. If it does the damage will be no different, it will trench the head, it's just less likely (according to VW) if there's no soft metal head gasket giving the flame front an easy place for a hot spot to start and then breach.

Other thing, it's not an "OH NO, WE'RE ALL GONNA DIE" thing, it's more like your doctor telling you to cut back on the smoking (or bacon, alcohol, extreme sports, whatever) or bad things could happen. Those bad things are more likely if you don't change your habits, but they aren't inevitable. There are lots of old guys who smoke, just not nearly as many as old guys who smoked as old guys who didn't. You haven't had a problem? Great.

You also don't need to believe VW tech bulletins (or anything else you read on the internet), but the next time you talk to an old-time VW mechanic (once again, that's a VW engine in your car) ask him about head leaks. He'll have a lot of interesting things to say.

EDIT: This horse is way dead and I'm done, but need to clarify that there ARE times when a head gasket is a good idea. When you have questionable machining from a flycut, for example, and lapping won't be enough. Or when have no other way to get deck height, are building a performance engine that will be torn down frequently, things like that. Or even when you just damned well want to, then all means go for it. (IMG:style_emoticons/default/biggrin.gif) It's your engine, so do whatever you want with it.