Does anyone know of the degree of engine failures using the new SM/SN oils without any supplimental zddp?
Some folks are saying it is No Problem.
Some folks are saying it is No Problem.
Flat tappet engine failures
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My flat tappet 305 has been running on SM/SN oils for probably the past 100k at least and compression numbers haven't been dropping. That has to be worth something.
Stock old valve springs on a stock engine your probably ok. Anything else you need the old style Zinc oil. Just about all oil companies make some kind of more Zinc oil. QS Defy, Joe Gibbs etc.
Why is that? What's wrong with SN oil?
Originally Posted By: oldhp
Stock old valve springs on a stock engine your probably ok. Anything else you need the old style Zinc oil. Just about all oil companies make some kind of more Zinc oil. QS Defy, Joe Gibbs etc.
Originally Posted By: oldhp
Stock old valve springs on a stock engine your probably ok. Anything else you need the old style Zinc oil. Just about all oil companies make some kind of more Zinc oil. QS Defy, Joe Gibbs etc.
The jeep 4.0 has flat tappits. Very few cam failures on the jeep forums. Maybe 1 a month divided by the thousands of members. The 05 and 06 are losing the gear on the cam but it's not the oils fault.
Plus there's milions of 90's and older chevy trucks and suburbans still running around and those are flat tappits too.
Plus there's milions of 90's and older chevy trucks and suburbans still running around and those are flat tappits too.
Originally Posted By: Chris142
Plus there's milions of 90's and older chevy trucks and suburbans still running around and those are flat tappits too.
In their defense it is pretty hard to kill a GM pushrod (minus a few exceptions).
Plus there's milions of 90's and older chevy trucks and suburbans still running around and those are flat tappits too.
In their defense it is pretty hard to kill a GM pushrod (minus a few exceptions).
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Old springs are weaker, require less protection on cam lobes/lifters.
By saying anything else I was referring to newer stiffer springs which in turn put more pressure on the lobes/lifters, which need more ZDDP to protect them.
By saying anything else I was referring to newer stiffer springs which in turn put more pressure on the lobes/lifters, which need more ZDDP to protect them.
Originally Posted By: oldhp
Old springs are weaker, require less protection on cam lobes/lifters.
By saying anything else I was referring to newer stiffer springs which in turn put more pressure on the lobes/lifters, which need more ZDDP to protect them.
Once the cam is wear hardened this becomes a moot point. With the tech in today's oils zddp is a dinosaur.
Old springs are weaker, require less protection on cam lobes/lifters.
By saying anything else I was referring to newer stiffer springs which in turn put more pressure on the lobes/lifters, which need more ZDDP to protect them.
Once the cam is wear hardened this becomes a moot point. With the tech in today's oils zddp is a dinosaur.
And the old oils aren't as high in ZDDP levels as we see through rose tinted glasses.
How does a camshaft get wear hardened in a engine?
Most of the time it is called work hardened. http://en.wikipedia.org/wiki/Work_hardening
Originally Posted By: AVB
Most of the time it is called work hardened. http://en.wikipedia.org/wiki/Work_hardening
Is that caused by use or by the manufacturing process?
Most of the time it is called work hardened. http://en.wikipedia.org/wiki/Work_hardening
Is that caused by use or by the manufacturing process?
I've always heard and read in the manufacturing process. It's like hardening the journals on crankshaft, the process hardens into the metal to a certain depth. That's why you can cut a crank .010,.020 or sometimes .030 and not have to get it re-hardened. Camshaft lobes are the same way with re-guard to the hardening process.
Work hardening can occur during use or machining. One example from the page that I linked was early copper tools. Copper can't be hardened by heat treating, but gets harder as it is hammered into shape. It can become hard enough to be brittle and needs to be annealed at that point, so that you can keep working it with out it breaking. I think that may be the same thing that causes a wire coat hanger to break if you bend it back and forth enough times.
I agree that the problem with the decrease in zinc is overrated in most cases. Blackstone posted some virgin analysis of oils bottled in the '60s-80s, and the zinc level wasn't all that high.
There are some notable exceptions to the zinc issue, as noted above , which are mainly old-school HiPo flat tappet engines with high valve spring pressure. And I think when breaking in a new cam in a flat tappet engine, the zinc levels are a bit more critical. Moly helps too, providing similar boundary protection while the oil is cool, before the ZDDP has time to activate from heat. I read about one guy who swears by putting heated oil (to 120-150F IIRC) into his rebuilt engines so the ZDDP is at it's activation temp. I can't remember but it's over 100F ... right?
There are some notable exceptions to the zinc issue, as noted above , which are mainly old-school HiPo flat tappet engines with high valve spring pressure. And I think when breaking in a new cam in a flat tappet engine, the zinc levels are a bit more critical. Moly helps too, providing similar boundary protection while the oil is cool, before the ZDDP has time to activate from heat. I read about one guy who swears by putting heated oil (to 120-150F IIRC) into his rebuilt engines so the ZDDP is at it's activation temp. I can't remember but it's over 100F ... right?
Originally Posted By: Shannow
Don't see cams work hardening much. "machining" is wet grinding. lifters are chilled iron.
It is simply not hot enough, right?
Don't see cams work hardening much. "machining" is wet grinding. lifters are chilled iron.
It is simply not hot enough, right?
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