Blew Head Gasket with 0 knock

[ekafrawy]

Well I just got through with installing my new alky control kit, tested out the system which worked just fine. Took the car out for some more tests. I started out with 17 psi without akly running fresh 93 octane and I would see barley any knock retard on my scanmaster. I made incremental increases in boost, and when I got to the 20 psi level the car would pull great through 4th gear with 0 knock. Alky was spraying, and then after making one last adjustment to bring the boost to 21-22 psi, I heard the pop, oil blew out the passenger side breather, and I could hear a very noticable hissing sound right under the intake on the passenger side. Blue smoke would come out exhaust when under throttle.
I then shut the car down, checked oil to see if any water got in, but it looked clean. Same with coolant. I managed to get the car home and I then noticed that I also blew a small hole in my exhaust right before the muffler.

So my question is why did this fail. Everything was running great, the car pulled hard, alky was spraying (set at 6 as mentioned in instructions) and again didnt see any knock whatsoever. The motor has 110k on it, and has never had the heads on intake pulled before so I know the gaskets are original. So is it just a matter of its old, and they lasted long enough or what?


Eric

 

[forzfed]

How much detonation has the car seen before? If very well could have been that, just weakened gaskets.

 

[ekafrawy]

Before I got the Alky kit I would see at most 3 - 5 degrees once in a while, like maybe on a hot/humid day. But the most boost I ran before the Akly kit was 17 psi on 93 Octane.

 

[818GN]

How full was your gas tank?

I had the same thing, blown HG w/0 knock and alky spraying, as a went WOT from a light with less than 1/4 tank of gas.

Gaskets were weak too

 

[ekafrawy]

I had a half tank of gas

 

[3.8L V-8 eater]

If in fact those are stock gaskets that have never been changed whos knows what there condition could have been being almost 25 years old...If they were weakened and you introduced over 20lbs of boost to em, it may have finished them off even though you saw no knock on that particular pull....There is good and bad here..The bad: you have some work time and money ahead of you..The good: you can now pull the engine clean everything up put on a double roller timing chain if it needs updating, port your heads etc...

 

[Jerryl]

In my mind , there are a few contributing factors to the failure;;

The scanmaster (I Ass-U-Me that is what was used to monitor for KR) may not have picked up the event(s).
In reality, it should since KR is typically progressive, but the slower reading of the scanmaster compared to PL may not have caught it.
(Since you stated that you saw KR in previous runs I am throwing out the possibility of a failing KR system. )

The HG could have been damaged before as previously described.
The higher boost was just the straw that broke the camels’ back.

If there was any pre-ignition, the detonation sensor aka “Knock Sensor” probably missed it.

 

[pacecarta]

did you verify map signal to pac controller
whats the condition of vac lines to the fuel pressure regulator and the map sensor , loosing a vac signal to either the map or FP reg will surely cause problems

what were the o2s during your test runs

 

[ekafrawy]

I replaced all vacuum lines prior to the alky install. I did confirm 1.6V at the green wire from the new 3 bar map sensor. When I made thta final run, I did not notice what the 02s were at. All I saw was that there was no knock reading on the scanmaster.

 

[turbofabricator]

I'm going with Jerryl here. Test the knock sensor to see if it is even working. Take a long 3/8" dr. extension and with the engine running, tap the block with the extention and see if it reads any knock. If tapping the block (actually stabbing it not using the extension like a hammer) doesn't register any knock, then there is something wrong. Bad sensor, cut wire, ect.

 

[ekafrawy]

Im almost positive it is working fine. Last week I saw some knock when I was driving it in 103* heat. But only 2-3 degrees. And sometimes when the tranny hit 2nd hard i get some false knock reading. so im pretty sure it works just fine.

 

[BlackBandit]

a few things here. One, knock is knock. It's still hella hard on things even at 17 psi.

two, this very well could be a result of 25 years worth of "light" knock. Keep in mind there was a dark time in the life of these cars when tuning was not as simple as looking at a scanmaster.

Three, if it was me I would check the knock sensor. Remove it, clean everything, and re-install at the proper torque. If it has any thread tape or it's not tight enough it won't be as sensitive.

 

[turb0buick57]

What boost level did the red/green led turn green?

Were you using 100% meth?

When testing the system did you test it with a little bit of water, and then add meth to the water once you verified it was working?
I guess what I'm getting at is could their have still been water in the bottle/lines from testing the system instead of 100% meth?

 

[ekafrawy]

From what i can remember, the red light came on around 7 psi then it went green somewhere around 10-11 psi.

I used 4 bottles of HEAT(Yellow bottles) I did not use any water.