What Causes This?
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FTE Legend
Joined: Jul 2010
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From: Northeast, OK
What Causes This?
No, this isn't a Ford. But, I'm curious as to what caused this and am sure you'uns will know. See the varnish on the rockers on the left, and the lack of varnish on those on the right? And, notice that it is uniform front to back?
This is a 7.3L from a '93 Suburban with 230K miles. The only reason it is down is because one soft plug let go and he knew that more of them were ready to go. So, to facilitate replacing them he pulled the engine. And, while on the stand he did a leak-down test and 7 of the cylinders had ~4 PSI leakage and 1 cylinder had 96% leakage. He pulled the heads and found carbon holding an intake valve open. Easy fix. And, there's so little wear in the cylinders that he can't get his fingernail to even hesitate on a ridge at the top. Further, he can still see crosshatch all the way around all cylinders. So, his use of Delvac (IIRC) and religiously changing the oil has paid off. But, what could cause varnish on one side and not the other?
This is a 7.3L from a '93 Suburban with 230K miles. The only reason it is down is because one soft plug let go and he knew that more of them were ready to go. So, to facilitate replacing them he pulled the engine. And, while on the stand he did a leak-down test and 7 of the cylinders had ~4 PSI leakage and 1 cylinder had 96% leakage. He pulled the heads and found carbon holding an intake valve open. Easy fix. And, there's so little wear in the cylinders that he can't get his fingernail to even hesitate on a ridge at the top. Further, he can still see crosshatch all the way around all cylinders. So, his use of Delvac (IIRC) and religiously changing the oil has paid off. But, what could cause varnish on one side and not the other?
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A wild guess would be the PCV system. If the breather is on one side, and the valve is on the other, then it would be sucking clean air into one valve cover, and sucking junk up and out the other cover with the valve in it. My theory may have merit if the PCV valve was located in the varnish side of the engine.
Post Fiend
Joined: Jul 2004
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From: Northern California
PCV system as franklin2 mentioned, one head being replaced and not the other, penzoil... Although penzoil usually is a lot worse and both sides...
Engine hotter on the one head compared to the other, water passage blocked... heat causes oil to break down faster...
All theoretical of course...
Engine hotter on the one head compared to the other, water passage blocked... heat causes oil to break down faster...
All theoretical of course...
Fleet Mechanic
Joined: Jul 2011
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I'm going to say PCV system. Like was mentioned, the PCV pulling all the crud onto the rocker arms and pushrods etc. on that one side while the breather on the other side keeps the others nice and shiny. I doubt it's a heat issue or a head being replaced.
If anything was replaced, I'd say rocker arms and pushrods. But, on a motor that's in as good a condition as what you say, I highly doubt they've been replaced, or the heads for that matter.
Glad to hear his motor isn't bad though. I wish my 300 was in as good a condition as that 7.3. That is a gasoline V8 isn't it? The 454?
If anything was replaced, I'd say rocker arms and pushrods. But, on a motor that's in as good a condition as what you say, I highly doubt they've been replaced, or the heads for that matter.
Glad to hear his motor isn't bad though. I wish my 300 was in as good a condition as that 7.3. That is a gasoline V8 isn't it? The 454?
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FTE Legend
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From: Northeast, OK
I'm betting the PCV'ers have it. I had not thought of that, maybe because the valve covers were off, but it makes sense: clean air in on the bank on the right and vapor-laden air out via the bank on the left. I told him you guys could solve it, and I'm sure you have. Thanks!
I'll also find out what oil he was using and the change interval. Obviously it worked well given the lack of a ridge, the crosshatch, and the fact the cylinders hardly leaked on the test. Oh yes, valve stem wear is almost undetectable, but the seals are a bit worn so will be replaced. And, the engine had never been apart.
I'll also find out what oil he was using and the change interval. Obviously it worked well given the lack of a ridge, the crosshatch, and the fact the cylinders hardly leaked on the test. Oh yes, valve stem wear is almost undetectable, but the seals are a bit worn so will be replaced. And, the engine had never been apart.
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