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Background

I did some work on my engine's head valves and their seats. This is a very old engine with very old/abused/invented/adapted parts, etc.

Both the valves and seats were in pitiful condition. In some cases, they required using a small chisel and hammer to get rid of carbon deposits! I even polished the chambers with a dremel, drill, etc.

I could push some of the springs down with my thumbs (it was hard, but doable) and still put the cotters (aka valve keepers, collets, or locks).

Other springs were really hard and wouldn't easily push down my bare hands.

What I Did

I did some lap, first coarse (150 grits), next fine (600 grits), and then put them almost mirror polish (that green dremel paste...).

When I tried to turn the valves with a very soft thumb push, they wouldn't rotate on their seat. I think this means they are matching tight. Is that correct?

My first leak test failed.

I put the spark plugs, valves facing up, then poured thinner into the chambers. None, but one put the port "wet", but not dripping. I took that one valve's springs off, relapped a bit, and put it back.

Now, almost all the valves are wetting the ports!

When I say "wetting", I mean: they don't flood, I can't see drops, but if I pass the finger inside, I can pick a very very thin layer of thinner.

When I poured the thinner to the top of the chamber, I couldn't really see the level drop at all in the 10 or 15 minutes I tried. I could see the meniscus just there.

Questions

  1. Are these softer springs damaged? Or, "barely" acceptable?

  2. Are my leak test results good "enough"? Or, are they bad and I need to relap?

BEFORE AND AFTER :)

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  • 2
    It sounds like at a minimum, you need new springs. If the springs had the correct seat pressure, you probably wouldn't have any leakage. You shouldn't be able to open any of the valves with your thumbs. – Pᴀᴜʟsᴛᴇʀ2 Nov 3 '16 at 10:08
  • 1
    Are the valves that are leaking the ones with the weak springs? – Steve Matthews Nov 3 '16 at 10:25
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    Watch this Jafromobile video and see if you are lapping correctly: youtu.be/7GEmuQa3dPY – Pᴀᴜʟsᴛᴇʀ2 Nov 3 '16 at 15:42
3

you need to look up the proper spring pressure for your engine. I can say with near certainty it sounds like your springs are bad.

How are you doing a leakdown test? If it is with the head on the block you may be leaking elsewhere besides around the valves. Rings or head gasket maybe. Could even be a small crack somewhere depending on how abused the engine was.

Were any valves replaced? if not are they stretched or bent?

Are the valve guides worn out and letting the valve sit crooked?

I would suspect your valve guides are a bit worn if you can spin them and suddenly they seal up.

.

Is this that skoda you posted about with the overheated engine?

2

Yes, it seems to be uneven springs, however I rotated each valve a couple of times left/right, with the springs in their positions, and now non are leaking. My test was: put the spark plugs and the springs in the valves, then put the head vertically with the ports looking up and filled there with thinner. The leaks where in the valves towards the chambers, not in the stem guides. Anyway, now they are not leaking, they stand about 1/2 hour without a single drop.

  • That's good that they're not leaking! I'm sure you know this, but valves naturally rotate while the engine is running. I'm saying that just because the valves don't leak in a certain position, it doesn't mean they won't rotate and leak while the engine is running. – Zach Mierzejewski Nov 4 '16 at 21:54
  • sounds like you might have worn valve guides. – Cc Dd Nov 4 '16 at 23:26
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    I wonder if the leak was because I didn't cleaned enough the valves and seats...hum...I did cleaned them with a rag damped with thinner, but could be perhaps debris left somewhere? because I rotated the valves back and forth and left them where they where (I marked their position with permanent marker, just out of curiosity) – Aram Alvarez Nov 5 '16 at 0:11
  • If this is that skoda that overheated in your other question then all that dirt buildup that was cleaned out of the valve guides could have worn down the valve stems or the guides and became the "new" valve guides. When you cleaned them they may now be very loose. – Cc Dd Nov 6 '16 at 10:56

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