daniel951

chris u know i had problems with the stock headgaskets blowing switched to MLS never had a problem from then on out with it.

TonyG

Chris was nice when he turned on the sarcasm switch, then turned it back off...

.... Because the logic is that flawed.....

You NEVER want to blow a head gasket. Especially in an aluminum bore engine... for ANY reason... EVER.

You will NEVER avoid engine damage blowing a head gasket. The damage occurs WAY too fast...



TonyG

cpt_koolbeenz

It appears everything I have read about fiber head gaskets being a form of cheap insurance is wrong... Apparently many people on this forum are guilty of spreading misinformation?

I got this "crazy" notion from these threads, to name a few:
https://rennlist.com/forums/944-turbo-and-turbo-s-forum/90896-which-head-gasket-for-me.html
https://rennlist.com/forums/944-turbo-and-turbo-s-forum/66068-head-gasket-copper-head-gasket-who-has-done-it.html
https://rennlist.com/forums/944-turbo-and-turbo-s-forum/113021-dead-head-gasket.html

Thinking that the head gasket is the weakest link in the combustion chamber, and cheapest to replace (out of pistons, valves, and the block) still seems valid. Is the head gasket not the weakest link in the combustion chamber?

I am not trying to prove anything... I'm seeking knowledge not flamage! Not sure why it needs to be a matter of "niceness" or not... If you feel the need to be sarcastic or whatnot, thats cool...
I just want the facts...



<<<You will NEVER avoid engine damage blowing a head gasket. The damage occurs WAY too fast... >>>

Thanks Tony... That is the first reason I have heard that opposes the "fuse" idea.
Do valves and pistons burn without head gasket failure?

Chris White

Yes, Almost all burnt valves happen with out head gasket damage.

Here is a short list of bad things that happen….

• Pre-ignition (pining, knocking) – if not corrected this will trash your pistons in a very short time. Pitting, erosion and eventual burn through. Long term ‘mild’ preigniton may burn the face of the head gasket causing failure. Preigntion is a very bad and destructive thing!!
• Burnt Valve – caused by the valve not seating correctly – the main cooling system is heat transfer from valve to head when shut. If some carbon build up blocks the valve from seating the valve head temps will soar and a pie shaped chunk will be cut out of the valve – in no time at all if you under high load.
• Overly Lean – See Pre-Ignition and add in high EGT.
• Overly Rich – this will cause carbon deposits – which are the prime cause of cylinder scoring.
• Oil consumption – See carbon deposits.
• Boost spikes – if the engine survives the brief preignition the over pressure may lift the head causing head gasket failure (stock head studs).
• #4 cylinder failure – one of the great unsolved mysteries. Many theories but no real proof yet. I favor the reduction in cavitation and nucleate boiling offered by non-aqueous coolants (see Evans coolants).

In most of these the engine won’t care what you have for a head gasket.

Chris White

sweanders

Bingo!

Laust Pedersen

There are a number of root causes for failures of fiber head gaskets (HG):

1. Inadequate clamping force from a) too low torque on cylinder head nuts (CHN), b) CHN’s were not properly oiled during the installation (too much friction), c) cylinder head not re-torqued.
Symptom: Oval fire rings.
Comments: There is a huge difference in the clamping force (for a given bolt/nut torque) for oiled vs. non-oiled threads.

2. Detonation (a.k.a. knocking, pinging, pinking, etc.) or pre-ignition which create up to twice the peak pressures and high temperatures.
Symptom: Compromised (pitted) fire ring(s) and sometimes pitted pistons, especially between the rings.
Comments: In my opinion the pitting is really cavitation induced by the shock wave (and its reflections), which is part of the detonation process. Pre-ignition is one of a number of causes leading to detonation.

3. Old age combined with use of questionable coolant.
Symptom: Rusted (and exposed) middle metal layer, which then looses its strength and buckles attempting to help hold the fire rings against the combustion pressure resulting in oval fire rings.

4. Partial hydro lock. Some unburned fuel in the combustion chamber at the end of the compression stroke, which will twist the piston by exerting a huge pressure on the quench (downward) side of the piston, when the liquid is being squeezed up toward the dish.
Symptom: Instantaneous break in headgasket and/or a cracked cylinder and/or bent rods above a certain rpm.
Comment: The unburned fuel typically comes from inadequate, intermittent or failed ignition. The failure is surprisingly silent since the piston approaches zero velocity close to TDC.

5. Full hydro lock. Unburned fuel in the combustion chamber at the end of the compression stroke at a volume larger than the combustion chamber volume.
Symptom: Instantaneous break in headgasket and/or a cracked cylinder and bent rods.

Laust

TonyG

>>>1. Inadequate clamping force from a) too low torque on cylinder head nuts (CHN), b) CHN’s were not properly oiled during the installation (too much friction), c) cylinder head not re-torqued.
Symptom: Oval fire rings.
Comments: There is a huge difference in the clamping force (for a given bolt/nut torque) for oiled vs. non-oiled threads. <<<

First off... you're correct, but even then there's a big difference depending on what oil you use.

Second, the above only applies to a fastner that ou are actually torquing to a value. On a factory TTY stud, you're are going to a trivial 15ftlbs or 20ftlbs (I forget), then 90 degrees, then another 90 degrees. In this case, the lubricant is irrelevant.

TonyG

TonyG

>>>It appears everything I have read about fiber head gaskets being a form of cheap insurance is wrong... Apparently many people on this forum are guilty of spreading misinformation?<<<

THAT'S WHY I INVENTED THE PATENT PENDING.... NO MORE WIVES TAILS ON RENNLIST BANNER (It was invented to ward off all the 911 wives tales.. but maybe it will work for 951's too!)

Guaranteed to ward off any Rennlist 911 Wives Tail! I thought I'd try it here to see if it works :-)

TonyG