superjet.1

If your looking for the mls cometic head gasket i have them in stock and am a cometic dealer you cant get it cheaper ill assure you that. I have them in several bores for both 2.5 and 3.0l blocks. just call thanks Travis

TurboTommy

Hi y'all. I 've bin reading this interesting thread and thought I would chime in here.

In responce to Tony about milling the head: don't know what the big deal is about removing some material ( unless of course it's been done already a few times in which case I would be questioning the integrity of the whole situation). I personally think increasing the CR is a good thing and i don't really know how it would affect cam timing. Also, when removing the head from a tired engine the mating surfaces will usually not be 100% flat. This absolute flatness, so to speak, is critical and makes for an enevitable milling job, IMHO.

In reviewing the causes of failed HG: there are many reports of horny speed freaks ( of which I am one) where driver holds accelerator to the floor in high gear and puff the HG blows! (I think this is the typical situation to induce failure) If this was detonation, wouldn't the knock control system of the engine management curb this pinging? I know there is a certain time delay between the onset of detonation and the knock control system to do something about it; but during this very short time, this kind of damage can occur? Shouldn't the car in question have gone into limp mode during or immediately after the failure? What am I not getting here? I'm not expecting a logical reply as this is a little off topic, but isn't anybody else curious about this?

TonyG

TurboTommy

>>don't know what the big deal is about removing some material <<


Exactly. Therein lies the problem with information passed through this list.

TonyG

Jon Schepps

TurboTommy,
Increasing CR is not necessarily a good thing.
Changing the thickness of the head changes the distance between the cam and the crank, effecting the timing -- not necessarily a good thing.
Depending on the knock sensor system to eliminate detonation problems is not a good thing.

There's no reason why these engines shouldn't survive repeated, prolonged full-throttle operation.

jls.

TurboTommy

I absolutely agree that depending on the knock control system to ward off HG failure is not a good thing; just questioning why it seems to have little effect.
Jon, I agree that it's not a good thing if the cam timing is affected. Just trying to figure out what that would have to do with the distance between the cam and the crank?

dand86951

Tony, I agree with your comment that you shouldn't mill the head unless you know what condition the head is in to start with, however Porsche recommends the head be milled to ensure it is flat and has the correct surface finish. The manual states a wear limit on the total amount that can be milled off from new, and it is a pretty liberal amount. The manual gives you .5 mm or about .020 in of material to mill off before they recommend going with a 1.4 mm head gasket. Most shops would only need to take off .001 to .003. Also as you said the list provides a lot of potential for incorrect info to be spread, and conversly it certainly provides a lot of good solid info to be spread.

TonyG

dand86951

Unfortunately, most machine ships I've seen will take quite a bit more than .001 - .003. Most will whack off .010 without blinking an eye.

dand86951

And that would be halfway to unusable assuming it was new to start with. I agree probably the most important thing is to have a knowledgeable shop do the work. And even then errors to happen.

Peckster

Milling the head won't affect valve timing.

Jon Schepps

It may be a very minor effect, but I think milling the head (or block) does have an effect on valve timing. The reason is that the cam and crank gear are connected by a toothed belt. Let's assume the factory designed the gear/belt tooth spacing such that when the cam and crank gears are at their stock separation, the cam timing marks line up perfectly when the crank is at TDC. In other words, at the proper belt tension, there is an exact integer number of belt teeth between the crank and cam when they are both on their marks. Now move the cam slightly towards the crank. The belt is now a fraction of a tooth longer. But you can't make fraction-of-a-tooth adjustments in the timing relationship between the cam and crank, so the timing will be off. Maybe its neglibly small, but maybe not. Shouldn't be too hard to calculate.

TonyG

Jon is correct. And the effect is to retard the cam timing.

TonyG

BC

Consensus on MLS gaskets 2 years later?

David Floyd

No problems with mine.

Ski

3 years on mine which is about 8500 miles, 15-17 psi, perfect.

Jeremy Himsel

2 years, 10K and 18 psi on my MLS. Not a problem.