Head Gasket failure...
Turbo Mini Forums

Hi all after some help. I'm pulling my hair out as to the head gasket failing into the water way.


I have to run a cometic solid copper gasket to help drop the Cr as I couldn't get suitable 998 +80 pistons with a dish in them. I ran the cometic gasket with a spray of blue holymer on the block side and then a gen minispares copper gasket on top.

The car was getting hotter on the drive home from Stanford Sunday, it never went over 95-97 deg but the rad and the fan were working hard. I shoved the block tester on and found that there was combusion in the coolant. I've just pulled head off tonight to have a look and to me the gasket looks ok but the cometic copper shim had dark water marks on the underside at Cyl 1 that were making thier way to the water jacket.

I cant see any signs of melting so I dont thing it det.

The head gasket did have a clear flakey substane on it which I have never seen before, looked like a coating that flaked off.

I have ordered new gaskets and a new maniflow manifold with with wideband bung in the outer cylinder pipes, I thought that I should keep a closer eye on the outer cylinders incase they are running too lean.

The head and and block were re-faced when I had the machine work done so they are flat and I used a new torque wrench last time I did the gasket incase mine was out.

I have also remeasured the CC's in the head and got the following:

Head 24.5CC
piston to deck height 0.45mm i have allowed 1.50cc
Head gasket 0.77mm crushed I have allowed 2.8cc
Cometic spacer 2.02mm I have allowed 7cc
1060 cc bore 66.61mm Stroke 76.2mm

This gets me to a C/R 8.42:1

Have I worked out the piston and gasket volumes correctly?

Some pics below, what are peoples thoughts on the failure and how to fix it?

I was thinking of dropping the stat down to a 73 from an 82 to help keep things a little cooler and maybe run two gaskets but I think that will drop me below 8 on the CR front ( well if I have worked everything out correctly....

Thanks for any help

Graham

I run a supercharger and I don't care the TB is on the wrong side.
VEMS + 12 PSI + Liquid Intercooler = Small Bore FUN!

Interesting, i have been thinking ahout using a decomp plate on my budget 998ti, very interesting that ist lasted so long,

Im not that experienced in reading head gaskets the ones of mine that have gone have been well and trully blown lol
But that does look like its been under clamped (last pic)
Can you 11 stud a 998?

Yes i moved to the darkside

Instagram @jdm_brett

you can 11 sud the small bores

i think id be dumping the spacer plate imo 10.2 is a fairly good number for static cr

what cam?

dont get so hung up on displaced/static compression ratio the cam plays a big part in what the combustion pressure will be!

im running my new engine with a bit under 11-1 compression ive tryed to make it det i put 15 degrease at 1krpm with a total 40 at 5k and it wont ping it just lost power so took it back to 9-10@1k and 34@5k my Toyota pinged its nuts off with anything more than std advance

time will tell once i get the turbo head on and all the turbo kit! i will be running the same compression as currently but thats just me and my setup

I had a solid copper plate made to get rid of the de-comp and gaskets. I used a sealant for belt and braces approach as well but that held up on a 1293 up to 150bhp.

This is running a supercharger and injection, right?

How does the cylinder head look? consistent colour across all cylinders?

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Paul I was thinking the same thing. I'm changing the exhaust manifold to put the wideband in the pipe for the outers. I will get some pics of the head up.

The copper plate is an original cometic I didn't realise at the time that is wasn't a proper gasket in terms of firing rings etc.

It's a bodge but I can't get the cr down without it as I couldn't find any dished pistons at +80.

Turbo this - it's an re13t at 112

Shellspeed what sealing compound did you run. Was it with a head gasket I too?

What do people think about reinstallation

Sealing spray on both sides?
Two head gaskets - I was thinking this was a bad idea due to the overlapping and bolt settings to get them both to crush.

I run a supercharger and I don't care the TB is on the wrong side.
VEMS + 12 PSI + Liquid Intercooler = Small Bore FUN!

No more meat to come out of the head, or a different head?

Our very own turbo Phil said there wasn't much more to come out as it had been skimmed in a previous life.

I guess I would need another 6-7 cc.

I would love a solution to get Combe out of the way. I guess a new un skimmed 295 might be more suitable

I run a supercharger and I don't care the TB is on the wrong side.
VEMS + 12 PSI + Liquid Intercooler = Small Bore FUN!

I might be tempted to bung up those big coolant holes close to the chambers on 1 and 4 and between 2/3 and run a commetic MLS big bore gasket

I run a home made mls with blue hylomar on it in the bike .never blown.

with the water inj on it ,I would run 9:1 cr maybe even 9.5:1.

I would say ,from the colour, that gasket has suffered detonation.

intercooler?

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

So you're using soft copper as a spacer between two even softer head gaskets ?

IMO that just sounds wrong

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

Robert is suck throughout so no ic

Steviet I have the copper plate which is a cometic gasket? And then and head gasket ontop.

It was sealed with blue Hylomar spray on the block side.

I run a supercharger and I don't care the TB is on the wrong side.
VEMS + 12 PSI + Liquid Intercooler = Small Bore FUN!

ahh i thought with the inj on it you could ic it by popping the charger on the front of the block .

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

It is running water meth 50/50 injection at just user 5 psi.

I will have another detailed look to see if I can see anything melting?

I don't have the skills to pop the sc on the front. I guess at that point I might as well switch to turbo, but getting a kit is also difficult

I run a supercharger and I don't care the TB is on the wrong side.
VEMS + 12 PSI + Liquid Intercooler = Small Bore FUN!

Either an un skimmed 295 or use a 940 head on it?

Would a Dry deck work?

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

I ran 2 bk450's for a while up to 12 psi , never blew , also my friend john is still running 2 450's at up to 10 psi , been fine .

I cannot remember if you can run 450's on a 998? prob not , that would give you around 8.9:1..

or 2 of the copper 998 ones,,,but then your into the 9.4:1 . which with enough water may work .

I have not seen a copper cometic , and I think like steve says I'd find a thick single gasket , say a mls cometic in steel ,and go for a 9:1 cr with such low boost .

also , have you thought of the possibility that the supercharger at that boost is more inefficient than at higher boosts ,and may actually make a hotter charge than running say 7 or 10 psi .

in case it helps , I ran the v8 in the tvr on water ,on 9.25:1 with a very open det prone chamber ,and with enough water could run 20 psi ,with high ex back pressure ,with no problem. with tat I would increase flow to the engine with a dashboard mounted valve until it started cutting out ,then decrease the flow till it as pulling hard . I allways ran as much as the engine could swallow while still pulling well. it ran a 12s 1/4 on low boost like that . it needed water from 7 psi on .

Robert

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Just for clarity, you can't put a large bore gasket on with a small bore head (well not without blocking up lots of the head's waterways).

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

www.twin-turbo.co.uk

Possibly pre-ignition rather than detonation. The problem seems to come from the area where the combustion chamber overlaps the bore. Have you got a nice chamfer to the bore edge in that area? Any hot spot could cause pre-ignition.

Before you actually change anything, I suggest that you make sure that you are getting enough fuel into the outer cylinders at part load. That's the holy grail of 5 port injection of any kind. Difficult enough with port injection but must be hard with just 2 large injectors sized for full power but running very low pulse widths at cruise.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

ah thanks wil I wasn't sure .

something else graham , looking at the inlet manifold design , I would expect 1 and 2 to run richer than 3 and 4 , 4 being the leanest of the lot with the charge robbing added in .it will be interesting to see if im right with the ego sensors in the outer legs of the ex .

may be worth playing with the idea of a water nozzle in the inlet wall directly opp the port for 3and 4 ,pressure balancing the water reservoir with boost .

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Blimey thanks all,

Robert but it looked like it had gone on cylinder 1.

I have cleaned everything and polished the copper gasket. Added the sealant and used a payer gasket.
The exhaust manifold has been replaced with a maniflow injection stage 2 lcb and man it's a fantastic fit, top quality stuff. Shame I couldn't stretch to the stainless version.

The exhaust sensor is in the middle branch. So we will know the are on the Outer cylinders.
I have used a 74 Deg stat and checked it worked.
I have two staged the head studs from 1/2 torque and then full.
I have 0.70 water jet maybe I need a larger one.

I run a supercharger and I don't care the TB is on the wrong side.
VEMS + 12 PSI + Liquid Intercooler = Small Bore FUN!

heres a pic of the head. the bright flakes you can see in the picture are from the minispares payen head gasket its seemed to have some kind of sealant on it., it was nothing I put on.

I run a supercharger and I don't care the TB is on the wrong side.
VEMS + 12 PSI + Liquid Intercooler = Small Bore FUN!

ah fair enough graham, got my which side of the gaket was 'up' mixed up lol.

so it was the copper plate to the block join that leaked ?

how much advance do you have on boost?

do you retorque the head after a few miles ?

it may be copper is just too soft for the job?

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Based on the picture of the head, I would say that your fuel distribution is OK, perhaps a little rich.

However, it only takes a minute or two running in a lean patch to cause a problem and it would not necessarily show up.

See what the wideband in the outers tells you. Can you log and plot the data?

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."