Imo000

So even if it’s true (it’s not), it sure as hell much more fun to have a boosted car, even if it breaks down every now and then, then to drive a stock one! Most of the HG failures are on old or original parts that were on their way out anyways.

Mark Anderson

Does Amzoil make a lifetime head gasket?

Mike Frye

I don't know, but of the SC-ed cars, I'll bet none of the ones that had a HG failure were running Amsoil.

AO

Mark's feeling frisky it seems today...

PorKen

So, Ernest is saying: Andrew = 800lb gorilla?

hacker-pschorr

AO

It wasn't my decision... it was my ignorance! Perhaps, had I known how much it was knocking upon installation and what that does to a motor, I would have made different choices. But that's all conjecture at this point.

I would modify your statement and say:

...you can't JUST "plug and play" an untuned supercharger without some serious risk.

1000% agreed! Most people tune for air/fuel delivery and stop there. That's only half the story... if that. The real science is in tuning for ignition!

Not sure what you mean... I got into the boost pretty much whenever I could. It was just too addictive. I thought Gretch was the same (unless he was making Moose Chili!)

Z

If you look through this forum you'll see that the majority of head gasket failures people have mentioned were on cars that were NOT supercharged. Mark Anderson posted about apparently blowing a head gasket on his normally aspirated stroker motor at Road America is just one recent example. Maybe there should be a thread on how going over 3,000 RPM causes head gasket failures, since the that would be a much more accurate statement than saying supercharging causes it.

There are thousands and thousands and thousands of supercharged car owners around the world who have sucessfully been doing it for decades and decades that would disagree with you.

To say that supercharging had absolutely no part in Andrew's head gasket blowing wouldn't be accurate either though. I'm fairly confident in saying that if Andrew's car would have never been supercharged, and he never would have gone over 3,000 RPM, and the coolant would have always been changed according to the service schedule from when the car was new, his 16 year old, 137,000 mile head gasket may not have blown... yet.

But it has historically been an effective way of keeping the messenger from making any more incorrect blanket statements.

Gretch

I will not defend supercharging, nor condem it......... I did it because I wanted to. I researched the risks and was able, through my choice of product, to ameleorate a high percentage of them.

I don't regularily "flog" my shark now, and did not, for the 95,000 miles prior to supercharging.

The car has just a bit over 101,000 miles on it. Maybe that is what E is referring to, ie a low amount of use???? I dunno.

I do know, that I thoroughly enjoyed the project of researching, purchasing, installing, tweeking and driving my Murph Supershark. Tim Murphy is a class act and I do not impress easily.

I really enjoy the car as modified and I would do it all over again, in a heart beat.

Damn near everything (exciting) that I do, has risks......... as this project did (and does). E is not wrong to point out the potential for risks.

I will say, that I highly value my 928 and have, since the day I brought it home in May of 1992. I have been careful with it because I do not want to do any harm to it. I am comfortable that I have not harmed it. If it ever needs a head gasket..... I will attend to that need as carefully as I have attended to all the work I have done on the car over the years.

The gorilla can go fluck hisself!

Fabio421

Just to stir the pot a little more.

Tarek blew a head gasket within 200 miles after the S/C install.

Important to note that he didn't install it and that as far as I know, there wasn't any spark tuning done. Maybe he will chime in and clarify.

Bill Ball

The detonation issue seems to be much more prominent in GTs. I'm guessing maybe due to the cams. My S4 only had pinging once when I bought some bad gas. Otherwise nothing. Sure, my SC is only at 5 PSI, but I've seen detonation in GTs at the same modest boost.

I have beaten the crap out this car - repeated burnouts, 170+ MPH runs for miles, averaging 145MPH for 100 miles. Zero motor issues (other than a manifold vacuum leak induced warm-idle lumpiness) with the SC for 20K miles, despite no tuning at all. Just a dyno check to make sure theA/F ratio was OK. Disclaimer - the SC has been off the car to meet CA smog testing. But during the 1.5 years it was on, the car was regularly brutalized with no ill-effects.

So, I may be all wrong about this, but I am more comfortable putting an SC on an S4 than a GT.

docmirror

Fire - here's some more fuel. My quals = None. Never built, nor owned a SC 928. Do currently own an SC Avanti, and SC Cord. Have owned an SC VW and turbo aircraft. what Ernie says as a direct statement may not be direct cause and effect, but let's say that it increases the probability of the gasket failure dramatically.

All SC installations on engines that are factory done have different C/R numbers, cam profiles, carb/FI maps, and ignition maps. This is true of the 1937 Cord, and of the latest SC applications on modern cars. The engines are tuned for the installation of the SC. In the case of the 928s, my understanding is that no changes are made to the C/R, cam profile, or fuel maps, but there is a change made to the ignition map. While this is beneficial for helping to control detonation, it' snot the only variable in the equation. What you need to remember is 14 degrees. Always, always, always, no matter what induction system you have, the max Internal Cylinder Pressure must occur at 14 deg after TDC. This is a fact of thermodynamics in a reciprocating engine.

Detonation is controlled by modifying ignition timing because detonation always occurs after ignition source. However, there's other factors at work besides just ignition. chamber design, stratification, C/R, etc all have an effect on detonation. Increasing the effective C/R through supercharging decreases the detonation margin of an engine.

So, I would say that without any other modifications to the entire engine, the SC process to the 928 does increase the probability of head gasket failure. The ringing of detonation causes strange things to happen in the combustioin area. High or spiky cylinder head temps are a sure sign of detonation. While the retarding of the timing will help, it will not eliminate detonation, just increase the margin of safety, because you are moving the peak ICP well past 14 degrees. In effect, you are giving up torque to control detonation.

I would say that the increase in temperature and then rapid cooling as the driver rolls off the throttle plays a large part in the failure of head gaskets. Detonation causes rapid and large cylinder temp increases, and if it happens as a cycle, this can be disastrious to the aluminum head in terms of warping.

BC

I am not really sure why a *last Century* technology fiber mesh headgasket that blew on a 100,000 mile, 17 year old motor that was not meant for any boost above atmospheric pressure is really an event? Its really a non-event. It allows Andrew to get that damn thing clamped down with some real studs, and an uprated (but albeit finicky on surface prep) cometic steel multi-latered headgasket and go for some real numbers.

This is like having a multple page thread about how someone took thier 100,000 mile 928 on a canyon cruise and came back thinking he needs new shocks. No ****! Its a wear item.

These things do not last forever, and there are better options now. A headgasket on a 100,000 mile motor getting boost is a wear item to be replaced as well.

ErnestSw

Docmirror,
Unless I misinterpret your post it seems you are saying that the 928 engine WAS NOT ACTUALLY DESIGNED TO BE SUPERCHARGED????
But then, why should any of those silly design parameters matter? Doesn't it feel good when you have more power----I rest my case.

BC

You are being wierd here Ernest. No, production wise, the car was not intended to be supercharged. But it has a very strong design that CAN be safely boosted to very close to one bar above atmo, as long as several key issues are addressed, one of which is a real headgasket, or at least one made when the second bush was in office and not the first!