Can you identify these pistons? & Valve problem

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sdutton007

Member +
Hi,

In my newest EP82 (running td05 at 1bar with emanage blue, fpr and uprated fuel pump) there was low compression in cylinder 3 and it was using oil. Figuring it was most likely to be the head gasket, I took the head off finding some pistons that don't look standard. Can anyone identify these:
akcv.jpg


The head gasket seems ok but one of the valves in cylinder 3 looks like this:
1gu3.jpg


That explains the low compression but would it explain the oil usage?

Cheers

P.s. I've got a spare head which has just been skimmed. I'm thinking of getting a 1.4mm athena head gasket, cambelt kit and arp headbolts.
 
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sdutton007

Member +
Cheers

Just out of curiosity, what could do that to a valve?

Someone suggested I get the pistons level, pour some white spirit in each cylinder to check the piston rings. Is this a good idea or will it rip the oil off the cylinder walls and posssibly damage something?
 
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AdamB

Member +
I wouldn't put white spirit down there, but a teaspoon of oil would be the better choice. If the compression reading then goes up, you have a ring sealing issue.
 
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sdutton007

Member +
AdamB said:
I wouldn't put white spirit down there, but a teaspoon of oil would be the better choice. If the compression reading then goes up, you have a ring sealing issue.
Click to expand...

Problem is the head is off now so compression tests are out of the question (without wasting hundreds of £££).

I have looked into this and various people suggest putting water/wd40/oil in each cylinder and see how quickly it leaks out. I don't think oil would be much help since cold oil is so thick it won't be able to get through small gaps anyway. So... water or WD40 ? Cheers
 
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AdamB

Member +
The problem is that won't really help your cause. Think about it, now the head is off its only going to disappear if there is a major leak or gap in the rings. Air is thinner than that of water or any liquid substance, plus the amount of force the air is under when the head is on its noticeably more than you could try with the head off.

If you've had a valve problem that you've found low compression with on that cylinder, your excessive oil may come from bits of valve hitting the seal and ruining it. Providing there is no excessive movement in the pistons I would bung the head back on and compression test it. At least you found out you had a forged engine, well pistons at least as a nice surprise.
 
Iain@CRD

Iain@CRD

Lifer
Was there a compression check done before taking the head off? When you say low compression how low are we talking?

It looks similar to an issue i had with leaking valve stems, it was allowing oil to sit ontop of the valves and when they got upto temperature parts of the valve where sitting to the seat and breaking off.
 
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sdutton007

Member +
AdamB said:
The problem is that won't really help your cause. Think about it, now the head is off its only going to disappear if there is a major leak or gap in the rings. Air is thinner than that of water or any liquid substance, plus the amount of force the air is under when the head is on its noticeably more than you could try with the head off.

If you've had a valve problem that you've found low compression with on that cylinder, your excessive oil may come from bits of valve hitting the seal and ruining it. Providing there is no excessive movement in the pistons I would bung the head back on and compression test it. At least you found out you had a forged engine, well pistons at least as a nice surprise.
Click to expand...

I see what you mean, but any liquid in the cylinders should escape through even small gaps due to gravity. Similar to how water can get out of a mug with just a tiny hairline fracture. Obviously the compression inside an engine is a greater force than gravity but if water can't gradually seep past then I can't really see thick oil being forced in. Especially when you consider that oil can only travel from the crankcase to inside the cylinders when the pressure inside the cylinder is less than the crankcase pressure. Or am I missing something here?

Iain@CRD said:
Was there a compression check done before taking the head off? When you say low compression how low are we talking?

It looks similar to an issue i had with leaking valve stems, it was allowing oil to sit ontop of the valves and when they got upto temperature parts of the valve where sitting to the seat and breaking off.
Click to expand...

Cylinder 3 was 1bar, rest were 9bar. This was done by cranking the engine about 10 times with fuel and spark disabled and throttle fully open.

I'm hoping it was just the valve, but want to be sure before I put the engine back together.

One of my mates told me to take out the pistons one by one to check the rings and put them back in reusing the bearings and piston rings. Is this correct, and worth the effort?
 
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AdamB

Member +
Its only under atmospheric pressure though, by all means give it a go you have nothing to lose but I don't believe it will prove conclusive.

9 bar/130psi is quite low but suppose its ok for a forged engine. If your going to go to the extent of pulling the pistons out, you may as well gap the rings, and check the piston-cylinder clearance. I wouldn't re-use the bearing shells for the sake of £90.
 
5e colin

5e colin

Member +
no man if u take pistons out the engine u chould fit new acl bearings and a new set of rings otherwise dont touch it
 
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Skalabala

Member +
That is obviously the valve that burnt away. Do not cheap out and sit with problems in the future.
Do the bearings and get a new set of rings :) Most of the work is done anyway.
And I personally will go with a 0.6mm head gasket with those -10cc pistons.
 
weeJohn

weeJohn

Lifer
While the heads off, it would be mad not to take the pistons out and check them, they can be put back in with no issues if everything is ok. It possible you may find a broken ring but you wont know until they are out. I would clean the ring lands well to check them thoroughly.

The valve problem has been caused by a closing problem, it has been allowing burning combustion gas to pass when it should have been closed, effectively overheating the valve edge and causing it to burn up. It could have been caused by it not seating properly, to much timing advance, bad cam timing or overheating in the cylinder.
 
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elison

Member +
Compression test done on my rebuilded forgie two weeks ago (after complete break inn) just to make sure everything is ok and got 160 across all cyl. Forged with domed wosnners and 1mm head gasket.

You would not be able to justify an failure with the water or spirit method because liquid will sip trough regardless a failure or not.

Cheers.
 
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