These are my new intake valves after 2000 miles. The pitting is wide spread but does not yet intrude on the sealing surfaces. Shell V-power nitro ( zero ethenol ) is the only fuel used. No fuel additives used. Ingested a liter of coolant a initial start up but after sealant correction no further loss. What is happening here ???
If there is something metallurgically wrong with the valves you might get a clue from polishing and etching the pitted surfaces like they do to check weld penetration. This video shows the technique. Skip ahead to about the 5 min mark.
Edit: you see might evidence of inclusions in the pitted areas and areas not yet pitted.
Rick OBrien
65 FHC in FL
Wow. Just out of curiosity, what made you look in the first place, after just 2000 miles? Way above my knowledge set of mechanical stuff. This is the only article I could find on a short search.
What is even stranger, is that it is the intakes, which will be cooler than the exhaust. There is a technique where a lab uses an electron probe to determine the composition of residue in specific areas. Company I worked for sent samples for testing when trying to determine failure analysis. Elements like chlorine would be seen around cracking in SS etc. @Mike_S might be aware of someone in NA that could look at metal failure.
I am curious as to what the tops of the pistons look like.
Dennis
69 OTS
No idea why they’re like that, but I’d replace them with some sourced from elsewhere.
Keith,
I can’t tell from the photo but has it happened to all valves?
is the pitting spaced radially around each valve?
Can you number the valves and take photo of each so we can see each clearly?
I have a gut feel it is corrosion from coolant.
Dennis
69 OTS
Thinking the same. All that those surfaces experience is water is warmed fuel-air mixture. Two are worse than the others - one carb?
I have to agree: pitting on intake valves, especially with few miles on it, is a complete mystery to me as to why that would’ve happened.
2000 miles might be the red herring.
How long were those valves installed? Months or years?
What was the coolant leak and how was it corrected?
Do I see some pits on the stems? Only a few exhibit the pits. Others seem to not have anything.
New valves or reground old valves? If old valves perhaps they were pitted long ago and cleaned up to work.
I am leaning towards coolant / water / moisture intrusion.
Got any pictures of the cylinders and valve seats?
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Good point: I made an assumption they were new.
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Keith
Did you put in the new valves or someone else??
Dennis
Where are you? I am in Vancouver
Thanks for all the input. ( I am in Ontario )
As mentioned , new valves at engine rebuild in2019. Unbeknownst to me, the intake manifold was warped so new gaskets and sealant would not prevent the ingestion of coolant. This took two tries resulting in several weeks of head scratching and no doubt, coolant, resting up against some of the intake valve where the leaks were the worst. It was bad enough to show coolant in the carb throats in the morning. The intake manifold had to be machined flat before it would seal. The antifreeze was Prestone " for all cars and metals " ( yellow ). The reason the head was off again is because I bent a valve adjusting shims and checking buckets in a quest to find an on going ticking problem.
Oddly , when the the intake manifold was off I notice heavy aluminum oxidation build up at the outlet of manifold after the thermostat. This was clean and smooth 2000 miles and three years ago.
Could there be a connection with this coolants ability to affect metals ?
System is now flushed and coolant replaced with Prestone Blue for European cars ( Jaguar 1998 and prior )
I have been out of the automotive industry professionally for over 20 years and can’t remember it all. What you have said leads me to believe there may be some electrolysis going on.
Although the coolant is drained now we used to stick a volt meter in the coolant and look for anything over about 200 mili volts.
I also wonder if the valves were closed and coolant sat on the back side of them for an extended period.
Hi Dan
Ya , i was thinking it was the closed valves only as well, but the electrolysis I idea is something I will definitely check !
I wonder if my cheapo volt meter will do the job ?
Valves are pretty tough metal I was thinking maybe some older valves used. The coolant would have to be old skanky stuff to do that
I still do the volt meter ck but new anti freeze depending on type is more resistant to electrolysis
They don’t want voltage floating around interfering with all those sensors running on .1 volts
Cheers
“……………Valves are pretty tough metal ….” Not enough to master chlorine.
The images appear to me to look like Chlorine attack. Valve material is peanuts to Chlorine it even eats Titanium that is why you cannot use Chlorinated water to wash jet aircraft.
Austenitic stainless steel (304, 316,et al) is prone to stress corrosion cracking in the presence of chlorides. High temperatures exacerbate the effect. Ferritic stainless steel (430, 440, et al) are relatively immune to chloride attack. Duplex stainless steel (2205) is also mostly immune to chloride attack. I used to spec 2205 Duplex for chemical plant storage tanks and dryers where chloride exposure was expected.
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I don’t believe that is correct. Titanium is very resistant to chlorinated water. We used the metal in seawater all the time for it’s chloride resistance and also recommended continuous chlorine injection in the seawater to prevent organism growth. The chlorine dosage would vary from about 3 ppm to many times that similar to doing a shock on a swimming pool
Temperature matters. Titanium does suffer chloride induced stress corrosion cracking at temperatures above 250C/480F. On a jet engine component the chloride will remain after the water has evaporated. I’m no jet engine expert, but I’m guessing there are lots of parts that operate above 250C.
Photo below: cleaned up random OEM exhaust (L) and intake (R) valves from a mid-70’s Chrysler 440 big block. Engine supposedly had 80,000 miles on it. This engine sat outdoors for years without anything covering the carburetor. I drained nearly 3 gallons of water from the sump before oil began to appear. Everything inside was covered in a rusty sludge. The exhaust valve is some unknown variety of stainless steel, the intake is a carbon steel alloy. You can see light pitting around the rim of the intake, but the exhaust still looks really good.
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