Gasoline-Engine Camshaft Wear: The Culprit is Blow

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http://papers.sae.org/892112/
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We were able to identify engine blow-by as a primary factor affecting camshaft wear in gasoline engines. Using a 2.3-liter overhead-camshaft engine, we isolated the valve-train oil from the crankcase oil and its blow-by using a separated oil sump. We find that: with engine blow-by, the camshaft wear was high. without blow-by, the camshaft wear was low. with blow-by piped into the isolated camshaft sump, the wear was high again.Later studies identified nitric acid as a primary cause of camshaft wear. It is derived from nitrogen oxides reacting with water in the blow-by. But even in the presence of blow-by, camshaft wear can be controlled by the proper selection of zinc dithiophosphates (ZnDTP) and detergent type.
Found a sequence IVA paper, which lead down a rabbit hole http://www.astmtmc.cmu.edu/ftp/docs/gas/...dure_draft4.pdf http://papers.sae.org/940794/
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An analysis was made of wear factors by investigating the effect of engine operating conditions on valve train wear. It was found that cam nose wear increased as larger amounts of combustion products, including nitrogen oxides and unburned gasoline, became intermixed with the engine oil. Based on these results, a valve train wear test procedure has been developed for evaluating cam nose and rocker arm wear under engine firing conditions.It has been confirmed that this test procedure correlates will with ASTM Sequence VE test and CCMC TU-3 test.
http://papers.sae.org/981445/
Quote:
A study of seasonal effects on a low temperature Valve Train Wear (VTW) test has been carried out with the Nissan KA24E engine test. Initial tests in our laboratory with this engine with an in-house reference oil showed that VTW was more severe in the hot and humid Japanese summer compared to the very dry winter. This prompted a systematic study of VTW performance using a temperature and humidity controlled cell, this being carried out with a JASO reference oil and an in-house reference oil. This work clearly showed that cam nose height loss correlated linearly with absolute humidity, higher wear being measured under higher humidity conditions. The slope of this relationship varied with the lubricant, presumably reflecting the differing sensitivities of lubricant formulations to humidity-induced wear. A relationship was also found between VTW and sulphate ion content of used oils. Overall, this study highlights the need to control ambient temperature and humidity for a low temperature VTW test.
http://papers.sae.org/962031/
Quote:
Continued interest in energy conservation and carbon dioxide emissions has resulted in enhanced opportunities for development of fuel efficient lubricants. This fuel efficiency has been achieved to a large extent by reducing viscosity as far as volatility and lubrication requirements allow. There has been much industry activity to assess fuel efficient lubricants without compromising engine durability. One area of potential durability concern is that of the overhead camshaft (OHC) rocker follower configuration widely used in modern passenger car engines. A motored cylinder head from an industry standard wear test having an OHC rocker follower configuration has been instrumented to measure oil film thickness (OFT) in an exhaust valve contact by means of an electrical capacitance technique. OFT measurements over the whole of the active part of the cam cycle are presented using both single and multigrade oils based on a variety of commercially available viscosity index improvers at an operating temperature of 100°C. Using single grade oils the measured OFT over the cam nose region was only slightly dependent on the lubricant viscosity for all test conditions. Under steady state motored conditions metallic asperity contact was absent and the surfaces were separated by an electrically insulating film which was present at all times. These observations would suggest that the dominant contribution to measured OFT is due not to viscosity but to the presence of anti-wear films on the metallic surfaces. The effect of adding VIIs to single grade base oils is to enhance the OFT in the predominantly elastohydrodynamic lubrication regimes in the cam flank regions of the cam cycle. However, little OFT enhancement could be found in the heavily loaded regions outside the cam flank regions when using multigrade oils. There is evidence that at higher camshaft speeds the measured film is composed of a surface film augmented by a small hydrodynamic contribution, however it would appear that the surface films laid down under lower speed conditions are more tenacious than those deposited under thicker film operation. Observed wear maxima on the cam follower surface occurred as predicted at positions associated with extended durations of contact with the cam. An apparent thinning of the film occurs (below that observed with single grade oils) when using lower viscosity multigrade oils, around the same positions in the contact cycle.
 
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Originally Posted By: Shannow
But even in the presence of blow-by, camshaft wear can be controlled by the proper selection of zinc dithiophosphates (ZnDTP) and detergent type.
End of discussion.
 

Shannow

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Originally Posted By: Linctex
Originally Posted By: Shannow
But even in the presence of blow-by, camshaft wear can be controlled by the proper selection of zinc dithiophosphates (ZnDTP) and detergent type.
End of discussion.
I'm hearing you there... just thought that the old papers were interesting, especially mentioned in the development of the Sequence IVA wear testing (purposely held at lower temperatures). One more set of factors that don't appear in RAT's absolute methodology.
 
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Originally Posted By: Linctex
Originally Posted By: Shannow
But even in the presence of blow-by, camshaft wear can be controlled by the proper selection of zinc dithiophosphates (ZnDTP) and detergent type.
End of discussion.
Well, one could, perhaps, discuss whether camshaft wear in fact is controlled by the proper selection of zinc dithiophosphates (ZnDTP) and detergent type. In recent spec phosphate-limited oils. with flat tappet camshafts. One could discuss it for quite a long time if one did not in fact know whether camshaft wear in fact is controlled by the proper selection of zinc dithiophosphates (ZnDTP) and detergent type. In recent spec phosphate-limited oils. with flat tappet camshafts.
 
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Originally Posted By: Superflan
I never experienced camshaft wear on gasoline engine. Or maybe there’s some but I’m not aware of.
I would bet money on it.
 
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I can’t say I have noticed any camshaft wear on a Petrol engine in my ownership and I put huge miles on Petrol engines back in the mid 90’s as a Courier and Private Hire driver in London as few of us had diesel till the late 90’s as fuel was cheap. But to be honest as the wear is gradual would anybody actually noticed until it caused Moreno noise or running problems I know people that had running problem with the VAG PD engine due to using the wrong oil and not changing oil regularly.
 
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I have done engine rebuilds with camshafts that were worn - not visibliy worn, but take a micrometer to the lobes and they are worn below spec.
 
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Older factory GM ones were the only ones I ever saw, '72 Buick 350 wore a lobe completely round, and an '85 Chevy 305 wore down several to the point that misfiring occurred, along with constant rocker noise. This was with older, SF or earlier rated oils, and no high lift cam.
 
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Originally Posted By: Superflan
I never experienced camshaft wear on gasoline engine. Or maybe there’s some but I’m not aware of.
I have lost a cam in a 350 Chevy. Rebuilt the engine,used the addatives the cam maker sent.ran it @2000rpm to break it in and lost a lobe during break in! Replaced the cam and lifters again and it lasted about a year. Flattened another lobe. The 302 in my 79 LTD lost a lobe. Replaced the cam and lifters in it. Ran a few years till I sold it. A real weird one was my mom's Dodge Omni with a 2.2....it lost the lobe for the fuel pump. The 340 I pulled out of my duster had a round lobe.
 
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CT8

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just thought that the old papers were interesting, especially mentioned in the development of the Sequence IVA wear testing (purposely held at lower temperatures). One more set of factors that don't appear in RAT's absolute methodology. [/quote]Rat actually has a few tests with 130*f oil and the pressure numbers are a bit lower that his optimal oil temperature tests.
 

djb

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Originally Posted By: Snagglefoot
In the bad old days of the early 60’s every engine had a vent tube and they let ‘er rip into the atmosphere. Check out the smog photos of LA back then . oilburner
The LA basin also had citrus groves that used smudge pots in the winter to prevent frost. By some estimates that was the largest contributor to winter smog. The solution was to cut down the citrus groves and build suburbs. (Of course this doesn't excuse the summer smog, which was clearly largely from motor vehicles.)
 
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8620 cam cores FTW! smile 8620 Carburized Nickel-Chromium-Molybdenum Camshafts Cam Motion's standard LS camshaft cores are our 8620 Carburized Nickel-Chromium-Molybdenum steel alloy camshafts. Our 8620 camshafts are a superior alloy to the 5150 cams and these cores also endure a more involved oven hardening process. This hardening process creates more durable wear surfaces on the lobes while maintaining the desirable ductility characteristics of the the 8620 alloy. The final product is a camshaft that is stronger with a more durable wear surface. Our 8620 cams are a superior product that are used in Top Fuel Dragsters, Funny Cars, Pro-Stock and more. The 8620 camshafts are available for all LS applications except VVT equipped engines.
 

CT8

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Originally Posted By: Superflan
I never experienced camshaft wear on gasoline engine. Or maybe there’s some but I’m not aware of.
FYI the cam and valve train are the highest sterssed areas of an engine.
 
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Originally Posted By: Linctex
High Carbon Steel cams are needed when there is a HARDENED tool steel roller rolling against it! grin
Or, worse yet, a hardened steel FLAT LIFTER sliding/grinding along it!
 
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Originally Posted By: bullwinkle
Or, worse yet, a hardened steel FLAT LIFTER sliding/grinding along it!
Yes, and no. The surface of a lifter is slightly convex. It rotates as it "rolls in a circular pattern" over a cam lobe. If the "convex goes away" - then, YES - the lifter will slide. But if all parts are machined properly, a lifter rolls in a circular pattern over the lobe, not slides.
 

Shannow

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Originally Posted By: CT8
Rat actually has a few tests with 130*f oil and the pressure numbers are a bit lower that his optimal oil temperature tests.
I sent him a question last year regarding the sequence IV wear test, and he added a whole new section on it...his test wins.
 
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Originally Posted By: bigjl
....in London as few of us had diesel till the late 90’s as fuel was cheap.
No it bloody wasn't. Don't forget, this is an American website. It is true that they started ramping up the tax (Fuel price "escalator"3% above inflation) in 1993 though.
 
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