Lifting the heads ?

[Mike T]

I'm asking this question because I really don't know. On our 8 bolt head configuration is lifting the heads something that happens at higher HP and cylinder pressure or is it only in conjunction with detonation?

I asked a good friend this question who has owned and worked on many fast Buicks but I'm curious as to what others have experienced and their opinion on this.

 

[BARRACUDA1968]

In my case I don't believe it was do to detonation. I had virtually 0 KR when mine lifted.

 

[Mike T]

In my case I don't believe it was do to detonation. I had virtually 0 KR when mine lifted.

I've been following your other thread and I think we both experienced something very similar.

 

[BARRACUDA1968]

I had more compression than my tune or fueling was set up for. Didn't know it at the time. After 900 ish miles of normal driving with a few short burst under 15 psi to seat the rings I decided to run at 18 psi from a 60 mph roll. I had a trail of smoke an 1/8th mile long following me. It was over.

Not sure what else could have caused it but I watched the SM and the WB religiously. My logs looked decent too. We figured I was in the 9.5 ish compression ratio. I was using the VR head gaskets and some say cometics would have been a better choice? Not sure how that equates to not lifting the head? I never broke the firing ring just lifted enough to fail the seal integrity of the head gasket. I do have signs of very high cylinder pressure after the tear down. I never saw KR above 2.5 and it was a blip on the log and went away.

 

[Nick Micale]

The head "lifting" is a combination to deformation of the head and block mating surfaces, and of course it is due to the enormous cylinder pressure from high boost and RPM.

Detonation may or may not play a part in this deformation, but it will certainly help it along.

When a large "hole" is blown in a head gasket, you can be assured that pre-ignition was present, and this can also be triggered by detonation?

Years ago when we first installed alum heads ,we found a noticeable increase in boost was possible, and still keep the head gaskets intact.

This was attributed to 2 factors, one was the added mass and structure of the alum head was a lot more resistant to deformation.

The second factor is the alum dissipates heat better than cast iron, so detonation and pre-ignition is less likely.

On a 14 bolt head, very seldom does a head gasket give away, but with elevated cylinder pressures, and mis-fire or pre-ignition, it must go somewhere, and a valve or piston will then become the victim.

Having seen lots of engine damage where knock retard, detonation, was never seen, that llustrates pre-ignition happens so fast it is not recorded?

Just because I have replaced about 2000 head gaskets on turbo Buicks over the past years does not make me an "expert" of what is going on in the combustion chamber, so this is just my opinion!

 

[BARRACUDA1968]

I wish I would have gone with the TA heads to start with. Until something jumps up at us looking things over I'm betting my problem was cylinder pressure. The chip probably had too much timing in it which I would have thought the knock sensor wouldn't have liked but like I said I never saw much KR to speak of. Not that KR is the end all of destruction but at any rate I get to start over.

 

[Mike T]

Great perspective on this Nick.

My car is not what would be considered a real high horsepower car compared to others that's out there ..it's making about 450 @ the wheels. In my case I will have to assume that my problem was due to a possible tune issue that was not presenting itself in my logs.

I did find a bad post on the coil pack that probably caused a misfire while it was under boost and that most likely finished the HG off.

Assuming tune is not the issue and you have a good mechanical seal, is there a horsepower level or cylinder pressure that the studs simply can't provide enough clamping force to maintain a seal?