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Home > Help Needed / General Tech Chat > Headgasket failure and deposits on valves and plugs

JackZwiebel

112 Posts
Member #: 11786
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Hallo guys,

my turbo engine with the SC EFI Kit did run quite ok already but now i have problem again.

I started a bit of fine tuning since it ran way too fat on almost all off boost areas. I am currently running a rather convervative spark ange (25 degree on transient to boost, 20 degree at full boost of 10psi) and too rich in all off boost areas. The off boost areas are not tuned propably yet. On boost it was tuned on the RR - also rather rich to be on the save side.

Now i noticed that it is burning quite a bit of oil - also i have a high pressure in in the head and the crankcase - pressing oil out of every possible opening (rocker cover, dip stick and so on). So i thought it would be the head gasket and i took the head off. The gasket itself looks fine - but the dark areas on the head itself look like it blew through somehow - what do you think?



Also i noticed quite a lot of deposits on the valves - with some of them been fallen off already (white areas on the valves). What do you think - should i worry bout it or is just from running too rich?

Best regards


steve1275

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Bromsgrove

Sounds like a problem with blowby, hence rings not head gasket. the deposits in the chambers probably caused by oil also.

'Where does the engine go?'


JackZwiebel

112 Posts
Member #: 11786
Advanced Member

thanks steve for your quick reply.
Rings only ran about 500miles since they were made new - also i did a leak down test (at the cold engine thought) with perfect resuts befor removing the head.
My guess would be if i had damaged rings after 500miles it would only be one zylinder (from det or something). Or is it just me not wanting to take the pistons out? *happy*

Isnt it possible that it blew through the head gasket where the dark ares around the stud holes are?


Steve220

144 Posts
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Shropshire

Did you tuner use any knock sensing whilst tuning? You say leakdown test, did you include a compression test?

What headgasket did you use?


shane

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2329 Posts
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Lowestoft, Suffolk.

I’d be inclined to pull the pistons for piece of mind to check the ring pack and ring lands.
It’s a pain to do but no point putting off the inevitable.

Shane


Mr Joshua

2328 Posts
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Luton Bedfordshire

Yep looks like piston material. Everything you have detailed points to piston and rings the deposit on the exhaust valve confirms it. I had the exact same issue so am confident that's where your issue is.

Own the day


Steve220

144 Posts
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Shropshire

Yep, without seeing the piston crowns, I suspect there's been detonation.


Joe C

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Carlos Fandango

Burnham-on-Crouch, Essex

Ive know leakdown tests to not pick up ring land issues, I think if the rings are good at the pressures your doing a leakdown they can seal ok, but once the piston is moving, or at combustiion presures then the piston wont support the ring and it will leak causiing blowby.

On 28th Aug, 2011 Kean said:
At the risk of being sigged...

Joe, do you have a photo of your tool?



http://www.turbominis.co.uk/forums/index.p...9064&lastpost=1

https://joe1977.imgbb.com/



JackZwiebel

112 Posts
Member #: 11786
Advanced Member

The rolling road setup was done with a det-sensor.

I did a compression test and a leak down test - both are fine and identical at all 4 cylinders.

Dont have a good picture of the pistons now - the only one i took:


and the head gasket:


Steve220

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Shropshire

What was your compression like on the test? What breathers have you got?


Rod S

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5923 Posts
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Rural Suffolk

The imprint of the gasket fire rings on your first photo look OK.
The imprint on the block face on your second photo look OK.
The photo of the head gasket itself looks OK (but only photo'd from one side)

No evidence whatsoever from those three photos of a blown head gasket.

The black stuff in the head chambers looks much more like oil than running rich.

And you said it's using oil.

A blown head gasket won't use oil.

And you said you have excessive crankcase pressures.

The oil itself could come from valve guides, knackered seal on the turbo compressor (just look in your inlet manifold or intercooler to ignore that one) but neither would give excessive crankcase pressures.

Like Joe says, a leakdown test - because it is static - will not necessarily detect broken ring lands because it's only when the engine is running that the rings move all over the place because they are not restrained.
As has already been asked, what is a compression test showing (ie, pistons moving up and down when you crank the engine to do the test ?)

If it's forcing oil out of every orifice as you said earlier when it's running, it has to be pistons/rings or you have totally inadequate breathers.

Schrödinger's cat - so which one am I ???


shane

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Lowestoft, Suffolk.

Many years ago I had a few issues that at the time remained unresolved and I was going through pistons at an alarming rate (Some of the more vintage members may recall).
The symptoms I would have are similar to what you are experiencing.
Compression and leak down tests would show nothing of concern but when the pistons where pulled the ring lands had cracked due to det.
My engine had also been set with det cans to listen for knock.
Shane


JackZwiebel

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Member #: 11786
Advanced Member

what i was thinking about are these dark areas i marked in the picture:


maybe it blew by because the head was not tight enough and the oil was lost because of the pressure that pressed it out?

i have a breather in the head cover with 1" diameter and the one on the crank case with 1" diameter.

anyway it seems like i have to pull the pistons - but since i rebuilt the whole engine the secound time 500miles ago and spend ten thousends and three years to get it running now i will give up in the turbo project now if there is a bigger fault again. Seems like i just dont get it running and build it back to a N/A...since i need new pistons then anyway.

an other question if i pull the pistons. Is the last oversize piston (+60) a problem because the walls are getting too thin?

Edited by JackZwiebel on 7th Oct, 2020.


Steve220

144 Posts
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Shropshire

Do you remember what you tightened the head nuts to?


JackZwiebel

112 Posts
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I didnt tight it myself, my engine builder put on the head when rebuilding the whole engine - but i was there when he put the head on and it was 61Nm (45ftlb) (I have the ARP Bolts)

My engine builder sayed there is no need to re-tight them. Maybe its the problem that i didnt re-tight them


Rod S

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Rural Suffolk

It would be nice to see a picture of the other side of the head gasket but from the one you have shown (top side on the head face ?) there is no sign of it being "blown".
Maybe a tiny bit of leakage between 2 and 3 but otherwise the gasket is perfectly intact.

The only issue I can see with it zooming as far as I can is that the fire rings seem to have a small lip on their inner diameter which would suggest that the cylinder head chamber diameter is a bit bigger than the gasket/bore diameter.
It may be an optical illusion from your camera (hence why it would be nice to see the other side of the gasket).

The oil stains on the head face could be from a "leaking" gasket, ie, one that has not yet visibly failed so the fire rings have not yet been blown away but, because of the excessive oil use and it showing in all your photos, it may just be from the sequence you dismantled the engine in, like if the chambers were full of oil and you lifted the front of the head first or you slackened the bolts and didn't actually lift the head until later.

But whatever those black marks are from, they do not explain excessive crankcase pressure blowing oil out of every orifice.

EDIT - just to add, if those black marks were from a small weep from the oily chambers - even though the fire rings are intact - you should be finding oil in your coolant or even bubbles coming up into your header tank (I assume you have a header tank as I see a front mounted radiator in one of the photos) because the holes in those areas are the coolant passages.

Edited by Rod S on 8th Oct, 2020.

Schrödinger's cat - so which one am I ???


JackZwiebel

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ok - one last thing. what do you think how dangerous it would be to put the head back on with a new gasket and see if it still has this high pressure? Is it risky do get a bigger damage if the ringlands are broken?


Rod S

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Why waste money on a new gasket ?

If you are just trying to prove a point, unless there is a reason you don't want to post a picture of the other side of it (maybe something else to hide ?) just use the old one for a test.

Not something I would normally recommend but the photo from one side only says the fire rings are fine.

So, provided you have found some other reason for the high crankcase pressure and fixed it, for a test I'd just re-use it - for a test only.
And if all your problems just go away, then fit a new one.

That is not a "blown" head gasket and even if it was, blown head gaskets do not pressurise the crankcase, they pressurise the coolant system.

You are just trying to put off the inevitable.

Running with broken ring lands will not initially damage the bores but when the rings break because they are un-supported, they will damage the bores.

And you say you are at plus 60 already so anything higher is either offset boring to 73mm or 73.5mm or liners back to standard.

Schrödinger's cat - so which one am I ???


JackZwiebel

112 Posts
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Advanced Member

oh, i didnt take a picture of the other side since it looks exactly the same - i know it doesnt look blown.

my cylinder walls were slightly damaged befor my last rebuild where the engine ate the crankcase breathing filter. My engine builder sayed i can go with a new hone since its not too bad and so i can reuse the pistons.

If i need new pistons anyway now i would go to plus 60 and have new cylinder walls. I looked at them now and beside the few acratches from befor the rebuild you can see a contact area further down. dont know if this is normal?


shane

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Lowestoft, Suffolk.

I had similar markings on my last catastrophic failure, detonation followed by a blown head gasket lead to high EGT’s and the resultant heat/lean mixture melted the piston and it looked as if it had expanded and picked up on the bore.
Out of curiosity what CC is your cylinder head and what compression ratio are you running?
You’ve mentioned several engine builds due to failures, have you made a significant jump in bore size increasing your swept volume and therefore your compression ratio?
With respect I will reiterate what has been mention above, you are prolonging the inevitable those pistons need to be pulled for inspection. What ever your findings with them and before running another engine you need to go back to basics and check everything, engine spec, fuel delivery system and ignition.
I missed an incorrect fuel pump for three years through stupid assumption that it was correct which proved costly.

Shane


JackZwiebel

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Member #: 11786
Advanced Member

since i am thinking of going back to n/a now i measured the cc in the head and the pistons. I have 27cc in the head, 12 in the pistons and the headgasket, resulting in a compression ratio of about 1:8.8.
10 psi should not be a problem with this CR.

The last rebuilt was because the metal filter in the crankcase breather got rusty from standing too long and fell down in the crankcase...killing the oilpump.

I am measuring the EGT from one of the outer cylinders - since im running pretty rich at the moment it does not go above 700°C on load...usually between 550 and 650.

i will pull the pistons in winter - i am just trying to wrap my head around what caused all this. And if it is worth keeping the turbo route since i spent 3 years and more money then im willing to admit without getting close to good running engine. I doubt investing more and rebuilding it as turbo will make it better and maybe should therefore go the n/a route where people around mehave more experience

Edited by JackZwiebel on 8th Oct, 2020.


Joe C

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Carlos Fandango

Burnham-on-Crouch, Essex

a few scratches...

id say the bores are toast, if those marks were from the last build then oils getting up past the rings, if they are fresh then, either the rings have not got enough end gap, or theybe been mega hot, or det has taken the ring lands out.

On 28th Aug, 2011 Kean said:
At the risk of being sigged...

Joe, do you have a photo of your tool?



http://www.turbominis.co.uk/forums/index.p...9064&lastpost=1

https://joe1977.imgbb.com/



Steve220

144 Posts
Member #: 11017
Advanced Member

Shropshire

On 8th Oct, 2020 JackZwiebel said:
- i am just trying to wrap my head around what caused all this


Possibilities:

-Using inferior or low octane fuel
-Inlet temps too high/poor map set up
-Overboost
-High engine temp
-Not running the engine in correctly, leading to oil mist lowering octane/carbon deposits creating hot spots or increasing CR.

Edited by Steve220 on 9th Oct, 2020.


JackZwiebel

112 Posts
Member #: 11786
Advanced Member

at the rebuild there were one or two scratches that you couldnt feel with the finger nail - so most of them are new.

Well i always used 100octan fuel, never got over 42°C inlet temp since i am using a huge front mounted intercooler, ran on the rich side with a wideband lambda, never over 10psi and the engine never ran hot since i mounted the huge front mounted radiator.

But i guess it is what it is - i will go to +60, new pistons to get the compression up to go back to n/a


Steve220

144 Posts
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Shropshire

Will be interested to see what your ringlands actually look like once you've pulled them out.

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