This is what todd did to my heads last minute... hopefully it will stay together... time will tell.

 

Projects of this nature require collaboration and team work among specialties in many different disciplines. All good tuners recognize their internal limitations, and solicit input from experts as necessary, particularly when breaking new ground. Look at the cars belonging to CJV, VRAlex and Markski – they all involve extensive collaboration among many different specialists. It is not unlike building a house . . . . except your house does not need to withstand tens of thousands of violent explosions per minute, exacerbated by 29 pounds of boost.

Craig

 

Any idea who makes EVO's headgaskets for them ? On the Supras when we used a "custom spec'd" headgasket for half inch studs we had a quite a few failures, going back to an enlarged stud OEM gasket fixed this problem. Another benefit is the ability to enlarge the OEM studs to 1/2" and/or using stock sized L19 studs. You guys will get it worked out in no time for sure.

 

On stock head gaskets no less.... I know of several ~1600+ HP Supras running stock head gaskets (modified for larger head studs)

Craig,

Is EVOMS installing stronger head studs? If there's no detonation and the head gasket fails about the only thing that can cause that is the head lifting off the block due to pressure and the gasket getting "burnt", if that's the case you will burn through a copper HG, or any other HG.

If they are installing stronger head studs perhaps they are not strong enough and they should consider larger ones. On very high HP, high boost (50+ PSI) Supras they usually run at least 1/2" studs. Also these studs are not meant to be re-used and it is strongly recommended that they are replaced any time the head(s) is removed.

Good luck with your project, your car sounds like an absolute beast!

 

Supra heads are aluminum, the block is cast iron. I think you meant to say that the block in the Supra is cast iron (true) and the 996 TT block is aluminum (also true).

 

I did a little research and was told, and its not coming from my mouth... except my evo 8 tuner who runs 8s in his car... that the one major thing that causes head gaskets to pop is too much timing.
I dont know Im not a tuner... but thats what I was told.
BTW- my evo 8 blew a gasket the second day after the engine was put together... we tuned it on C16 but the gas was bad and detonated...
Thats all it took.
markski

 

how is the tranny holding?

 

Too much timing can cause detonation which can of course cause a HG to pop. Other than that I am not aware of any other reasons why too much timing (without detonation) would cause a HG failure other than the fact that cylinder pressure is greatly increased when the timing is very aggressive. This could then of course cause the head(s) to be lifted and burn through the HG.

 

These things happen, I think that experience in similar builds is what makes you know where the thresholds are. The sealing and tightness are very important but nothing can hold unless the programming is adjusted. Detonation cannot be contained, something else will brake.
Correct. It is the detonation that causes the heads to lift, not boost in itself. Aggressive timing (for more torque/HP) causes detonation, and when knock sensors (whose job is to detect vibrations 5-10KHZ related to knock, and then pull timing until the vibrations cease, again and again) are not capable to pull timing fast enough to compensate (because of the continuous high boost pressure being fed) then..bang. These ECUs do not "see" Boost as such. Improving sealing is very important, but it just retards the lifting from happening, unless the tuning is done within the limits.

These situations can be avoided if the engine is tuned extensively on a properly cooled engine dyno room before being tuned on the street.

 

VERY good points.

There are a few factors that can cause a head to lift without detonation, most of the time a combination of some of these causes the issue, such as:

A) Head bolts/studs that are not strong enough
B) Head bolts/studs that are not tightened (not enough torque) down enough
C) Very high cylinder pressures which can be caused by very high boost levels, too much timing as well as other factors.

I however agree with you, the vast majority of the time head gaskets fail is due to detonation, which lifts the head(s) and allows the HG to get burnt.

 

Thanks for all the input guys. This is precisely what makes 6Speed so great. The collaboration and sharing of knowledge.

EVOMS specifically looked for any signs of detonation, as that was an obvious possible cause of the gasket failure. This was the very first thing EVOMS did upon removing the heads. Detonation leaves evidence. There was NONE present here. I repeat: no signs of detonation. In fact, it appears that I may have been a bit on the rich side. I have an AEM wide band a/f gauge and it showed very safe ratios. The last thing EVOMS wants is to tighten up the sealing, but allow detonation to continue, such that the pressure gets released some other way (e.g., through a ventilated engine). Therefore, they are making absolutely sure that I did not, and I do not, have any detonation.

Yes, my gasket failed because my heads lifted (and/or rocked). However, heads will lift/rock for reasons other than detonation. Stated another way, detonation is NOT the cause of all gasket failures. Rather, excessive pressure, beyond the capacity of the existing gasket/head studs/stud torque/sealing combination will cause gasket failure even if no detonation is present. This is not unusual in high HP forced induction applications.

I was already using upgraded head studs. I am now switching to a recently released head stud that should enable me to apply even more torque. Previously, my head studs were limited to about 42 psi. My new studs will enable considerably more torque (hopefully, somewhere in the 50s – EVOMS is testing this). That is a huge difference!

The copper gasket and o-ring will also provide a FAR better seal than a traditional compressed gasket and no o-ring. These problems are not uncommon in high horsepower, high boost applications, and that is precisely why Indy cars and other high horsepower cars utilize copper gaskets and/or o-rings to ensure a better seal. Copper gaskets and o-rings do not exist merely to compensate for detonation, as that would lead to engine ventilation. Rather, these products exist precisely because, even without detonation, additional measures are sometimes necessary to handle the additional pressure, particularly in high HP, high boost applications.

Of note, both VRAlex and Markski are using o-rings on their heads. They are doing this because, notwithstanding the lack of detonation, they need a stronger seal to handle the tremendous pressure. VRAlex also experimented with a copper gasket. Out of respect, I will not disclose other instances of head gasket failure encountered by other tuners, but suffice it to say that I am not the first.

With regard to Supras, they are in a completely different boat. With the larger head studs and cast iron block, the head studs can be torqued down MUCH, MUCH more than on a 996TT engine (I seem to recall hearing something like 60-70 psi). This additional torque permits a FAR stronger seal. BTW, the same is true for Evos. The 996TT’s aluminum block simply cannot withstand that much torque without distortion/reflection. Therefore, alternate measures are necessary. Again, these alternate measures are commonly used on aluminum block engines that need to withstand pressures beyond the capacity of the OEM parts (even when no detonation is present).

Finally, someone asked about my tranny. It is doing great!! In fact, it appears to be putting down the power better than my OEM tranny.

The new gasket and o-rings are supposed to arrive today, and thus begins the reassembly.

Craig

 

o-rings.. old skool style... heheh

best thing to have is to actually have no gasket......

 

You are absolutely right! And there is a reason for that. They work!

Again, you are absolutely right. Many Porsche racing teams used to (and may still) weld the heads to the case in order to handle the pressure. They skipped the head studs, o-rings and other measures, and simply permenantly welded everything together. This makes for a great seal, but impairs any further engine work. Of note, these Porsche teams did not weld the heads on simply to compensate for detonation, as they would have ventilated the engine. Rather, they welded the heads because, notwithstanding the lack of detonation, heads will still rock/lift when the pressure/power/boost exceeds the capacity of the existing seal.

Craig

 

Alex runs only 1.5 to 1.7 bars of boost MAX on C16 . no more then 1.5 bars on 110.
Im supposed to be somewhere around the same ... maybe ur boosting too much ???
maybe 28 psi is alot for 110. Im just speculating.
what do I know- I dont even have the car yet. LOL

 

Incorrect. He has run 2.1 bar. Moreover, his larger turbos likely generate more pressure at 1.7 bar than mine do at 1.9-2 bar.

Craig