Heads lifting under boost

[Robbbyg]

Hello , im referring to a prev post, Mr Fairman made a good comment when noticed a small amount of oil near where I was installing air plugs and said that this can be from head lifting under boost...I didn't follow it up at the time but obviously it cant be a good thing.. Q: I don't want to stop boosting, so what do I do, do I retorque?? if so how much around 30? If so can someone send me a link on howto? cos im not sure which nuts I should tighten, (serious), If other questions cant be helped with pls I need a link or pic showing exactly the nuts that hold the head down so I can at least take photos of them and post here for opinion. OR do I drop the spring on WG to a softer one and do nothing with the nuts? Advice BTW: this is not a joke thread I do want to know how to do this thx

[Tippy]

I'd say, turn the boost up within safe CIS capabilities and forget about it.

[Robbbyg]

OK that's easy then

Im also thinking/wondering that if heads do lift under boost then its sort of acting like a buffer against pistons blowing up because the pressure is relieved between the head and block???

But the problem is that when it happens acceleration is lost! once the pressure is reached it lets go and with it the power doesn't make it to the rear wheels

So whats the solution? I don't want to add a gasket as that would most likely lower compression and in turn lessen power to the wheels..

Anyone got a link?

[Akila]

Ni Resist Rings - Rennlist Discussion Forums

[Robbbyg]

Good information,
I dont feel Porsche left that out on purpose though I think that it was just probably never thought of at the time, maybe they didn't do enough miles before release for the problem to arise.

Because the expense would have been neligible in comparism to the sodium filled valves and nikasil pistons which were standard,

Most likely an oversight id say

But that solution is out of my resources unfortunately...one day

[Tippy]

No pressure is lost. The highest pressure is when the piston is near top dead center - well above cylinder and block mating surfaces.

I'm on the side that believes heads do not lift...

[RarlyL8]

I would think if the heads were lifting you would have stripped or broken head studs. No other way they can lift. The sound of broken head studs is unmistakable ...

[Ronnie's.930]

Originally Posted by Robbbyg

Q: I don't want to stop boosting, so what do I do, do I retorque?? if so how much around 30?
If so can someone send me a link on howto? cos im not sure which nuts I should tighten, (serious),

Robby, best not to retorque the head stud nuts in your engine . . . they are made of a notoriously horrible alloy called Dilivar that has been known to break even when new/just installed on engines that have not yet run. The most you would want to do is to lightly check each one with a ratchet just to make sure that none are loose. Retorqueing is asking for trouble and you would most likely snap a few of them off.

Regarding the oil seepage - there is nothing you can do about it without disassembling the top end, having the mating surfaces checked for flatness (and having them machined accordingly) and installing superior head studs. Does the amount of seepage mean you must do this now? Absolutely not - not nearly bad enough if none of the studs are currently broken. For the time being, simply stick to reasonable boost levels like Tippy said (best to stay at or below .8 BAR with the OEM intercooler).

And PS - smooch it, bub!!!

[timspu]

When i first bought my car i had a funny banginig noise when on boost only sounded like the wastegate banging. It tuned out to be lifting heads due to a broken head stud.
i still have an oil weep around the head but believe its from the rocker cover.

Do you have a banging noise when on boost? Gas leaking from the lifting head or just the ehad chattering on to the barrel.
Mine went on for about 6 months before i had the top end rebuild.

Hopefully you only have a slight oil weep,

Tim

[TurboKraft]

Originally Posted by Tippy

I'm on the side that believes heads do not lift...

I've heard both high boost Turbos and high compression RSRs lift their heads, despite running 993T head studs. What does it sound like? Tap the fins of a cylinder head and they make a characteristic ringing sound. You can hear that over the roar of an RSR exhaust or an open wastegate.

But back to the OP and the idea of having oil leak out from between the head and cylinder -- if that were to happen, you have much bigger problems on your hands because there shouldn't be any oil in your combustion chambers.

[drmatera]

Heads do lift. But it doesn't mean they need to be fastened tighter. Make sure you have no detonation, and the head studs are not broken. Then boost on my friend

[TurboKraft]

Correct, definitely DO NOT fasten tighter. That's a sure way to warp cylinders and heads.

If you think the factory studs aren't holding, that they've weakened and/or stretched, then try loosening, lubricating and re-torquing (pray none snaps), or replace them.

[Tippy]

Quote de Tippy

I'm on the side that believes heads do not lift...

I've heard both high boost Turbos and high compression RSRs lift their heads, despite running 993T head studs. What does it sound like? Tap the fins of a cylinder head and they make a characteristic ringing sound. You can hear that over the roar of an RSR exhaust or an open wastegate.



But back to the OP and the idea of having oil leak out from between the head and cylinder -- if that were to happen, you have much bigger problems on your hands because there shouldn't be any oil in your combustion chambers.

Oh great, I have 993TT studs an plan on 2.0 bar just for *****s and giggles on race gas.

[Spenny_b]

Originally Posted by TurboKraft

I've heard both high boost Turbos and high compression RSRs lift their heads, despite running 993T head studs.

I guess that's why the Works team welded the barrels to the heads on the 962, Chris? (and 956 possibly?)...or is that urban myth?

S

[Robbbyg]

Originally Posted by timspu

When i first bought my car i had a funny banginig noise when on boost only sounded like the wastegate banging. It tuned out to be lifting heads due to a broken head stud.
i still have an oil weep around the head but believe its from the rocker cover.

Do you have a banging noise when on boost? Gas leaking from the lifting head or just the ehad chattering on to the barrel.
Mine went on for about 6 months before i had the top end rebuild.

Hopefully you only have a slight oil weep,

Tim

Hi , No I odnt have any of those symptoims, only symptom is an oil stain around near where theright side exhaust manifold connects,

Today ill take a spring our and go back to .8 bar to be safe,

[Ronnie's.930]

Originally Posted by Robbbyg

Hi , No I odnt have any of those symptoims, only symptom is an oil stain around near where theright side exhaust manifold connects,

Today ill take a spring our and go back to .8 bar to be safe,

Robus-maxxximus, that's definitely a good idea as it is really playing with fire to raise boost beyond stock settings without being able to verify/monitor safe air/fuel ratios . . . can run out of fuel and have detonation problems in a hurry by increasing boost pressure and not increasing fueling via an adjustable WUR.

[RarlyL8]

Proper AFR's are just the baseline at that point. If the octane of the fuel isn't high enough bad things will happen fast. Engines need special build parameters to support high boost levels and high octane fuel which can burn hotter than gasoline depending on the mix. Typical OEM head studs and hardware are not used. I have seen pictures of heads welded on race engines, now THAT is hard core!

[Robbbyg]

Originally Posted by RarlyL8

Proper AFR's are just the baseline at that point. If the octane of the fuel isn't high enough bad things will happen fast. Engines need special build parameters to support high boost levels and high octane fuel which can burn hotter than gasoline depending on the mix. Typical OEM head studs and hardware are not used. I have seen pictures of heads welded on race engines, now THAT is hard core!

I guess I have been lucky so far,
I think the low compression of 6:5 to one plays a part in reliability,

Even with all my later 930 bits ive added im going to go the smaller .8 spring doesn't worry me really as even when driving her around town she is torquey enough before boost anyway.

Im just peeeed off at myself for installing the air plugs , should have left it alone all it did was give me unnecessary work in fixing leaks.

anyway back to my New Paintjob, I call it Marrow Blue (my own invention)
It goes on really nice and shiny ,but time consuming ill have to buy some wider brushes

[Tippy]

You are paintbrushing your car??

[Ronnie's.930]

Originally Posted by Tippy

You are paintbrushing your car??

I'm confident that is some Robby humor right thar! Regardless, the bulk of the paint is undoubtedly going straight up his nose!!!