[Z06] Interesting read on guide wear
02-25-2014, 08:47 AM
#1
Safety Car
Thread Starter
Interesting read on guide wear
Found this when I was researching bronze guides, it was posted on an Evo forum but is very relevant to any performance head application and in my belief why we are seeing so much guide wear.
"I found this while googling
Myth: Bronze guides don’t last.
Fact: Early silicon based bronze alloys used in valve guide applications quickly earned the reputation of having poor wear performance. It wasn’t until high nickel based bronze alloys (AMPCO 45) were introduced that the valve guide market was able to offer a superior bronze valve guide, suitable for high heat applications (Nitro-methane etc&hellip
.
But still, people realised that that material was not lasting as long as cast iron. One of the main reasons is because this material needs to be fit at a looser clearance to prevent seizing problems.
After extensive research, the majority of automotive and motorcycle racing head manufacturers and rebuilders are now installing manganese bronze alloy guides. The two principal advantages of this alloy is superior heat transfer and also that the engine builder is able to fit the guides at a tighter clearance for a better oil film control and longer life. We should call this alloy ‘’zinc bronze alloy’’ instead of manganese bronze because it contains nearly 30% zinc, 2-3% manganese. Manganese is the hard part of the recipe and the zinc is the bearing ingredient, a material which is also a self lubricant.
Myth: Why use manganese bronze alloy when I know that a stock Evo or Twin Cam guide can last 60,000 miles or more?
Fact: It’s true that for stock replacement, cast iron guides work fine. However, the problem starts with the high performance applications. In high lift applications, the guides need to be shortened. With more heat and side load from the valve involved, the oil film between valve and guide deteriorates more quickly. In addition to increased viscosity breakdown, cast iron guides are also an abrasive material which induces the premature wear that we’re used to see with this application. In cases where valves have collided with each other or with the piston, cast iron guides have been found to fracture and deposit damaging fragments into the cylinder and combustion chamber. This is not the case with manganese bronze guides.
Here they talk about premature wear but it seems that if OEM's are using cast iron and chrome stem valves for longevity that combo should be fine in most applications unless you're going the high performance route.
Chris"
After looking at all the heads coming back from WCCH and other head builders I am seeing the same common theme, longer bronze guides. The one thing the LS7 has that no other LS motor has is 1.8 rockers and a .595 lift, much higher than any other LS motor. Reading this post from 2008 on an Evo forum makes it clear to me this is a universal truth in performance heads that a short PM guide will wear out with a high lift cam, and the longer bronze guides help eliminate the side loading and heat in the guide.
"I found this while googling
Myth: Bronze guides don’t last.
Fact: Early silicon based bronze alloys used in valve guide applications quickly earned the reputation of having poor wear performance. It wasn’t until high nickel based bronze alloys (AMPCO 45) were introduced that the valve guide market was able to offer a superior bronze valve guide, suitable for high heat applications (Nitro-methane etc&hellip
. But still, people realised that that material was not lasting as long as cast iron. One of the main reasons is because this material needs to be fit at a looser clearance to prevent seizing problems.
After extensive research, the majority of automotive and motorcycle racing head manufacturers and rebuilders are now installing manganese bronze alloy guides. The two principal advantages of this alloy is superior heat transfer and also that the engine builder is able to fit the guides at a tighter clearance for a better oil film control and longer life. We should call this alloy ‘’zinc bronze alloy’’ instead of manganese bronze because it contains nearly 30% zinc, 2-3% manganese. Manganese is the hard part of the recipe and the zinc is the bearing ingredient, a material which is also a self lubricant.
Myth: Why use manganese bronze alloy when I know that a stock Evo or Twin Cam guide can last 60,000 miles or more?
Fact: It’s true that for stock replacement, cast iron guides work fine. However, the problem starts with the high performance applications. In high lift applications, the guides need to be shortened. With more heat and side load from the valve involved, the oil film between valve and guide deteriorates more quickly. In addition to increased viscosity breakdown, cast iron guides are also an abrasive material which induces the premature wear that we’re used to see with this application. In cases where valves have collided with each other or with the piston, cast iron guides have been found to fracture and deposit damaging fragments into the cylinder and combustion chamber. This is not the case with manganese bronze guides.
Here they talk about premature wear but it seems that if OEM's are using cast iron and chrome stem valves for longevity that combo should be fine in most applications unless you're going the high performance route.
Chris"
After looking at all the heads coming back from WCCH and other head builders I am seeing the same common theme, longer bronze guides. The one thing the LS7 has that no other LS motor has is 1.8 rockers and a .595 lift, much higher than any other LS motor. Reading this post from 2008 on an Evo forum makes it clear to me this is a universal truth in performance heads that a short PM guide will wear out with a high lift cam, and the longer bronze guides help eliminate the side loading and heat in the guide.
02-25-2014, 09:05 AM
#2
As far as the LS7 goes, the guide length issue may be a bit overstated... the OEM PM guide is 2.1" long, the CHE bronze guide -- that was at least at one point in time used as a popular replacement -- is 2.2" long (this is where the first 'longer guide' claim originated).
A 5% increase in guide length would surely help, but how much or how critical is another issue. And this is assuming the head porter does not grind off the extra length (which protrudes down into the port), as has been seen sometimes.
It is seeming more and more likely that if wear is induced, for whatever reason, then the OEM PM ('cast iron') guide will suffer worse than a bronze alloy guide (for the reasons stated in the article, which was a good one -- thanks for posting
).
A 5% increase in guide length would surely help, but how much or how critical is another issue. And this is assuming the head porter does not grind off the extra length (which protrudes down into the port), as has been seen sometimes.
It is seeming more and more likely that if wear is induced, for whatever reason, then the OEM PM ('cast iron') guide will suffer worse than a bronze alloy guide (for the reasons stated in the article, which was a good one -- thanks for posting
).
02-25-2014, 09:18 AM
#3
Safety Car
Thread Starter
I spoke to Richard this week he said he's using another local supplier on his bronze guides, from some of the pictures and videos I have seen you can clearly see that the bronze guide is longer than the stock. I wonder if he's using longer guides now?
02-25-2014, 02:28 PM
#4
This is the question I asked him...
" I saw a video today of your heads with 12k miles onm them without any issues, and the guy who was doing the commentary said that he guides were 1/4 of an inch longer. Any reasoning for this?"
Reply:
"We use a .200" longer valve guide to provide additional support for the longer LS7 valves. GM chose to use he same valve guides as those installed in the LS1,2&3's and those valves are shorted than the LS7's by almost .300"."
02-25-2014, 02:47 PM
#5
Pro
If the valve guide material and length were the problem, ALL of the LS7s would be having issues. Also, the LS9 has had its share of issues with worn guides...and it has much lower lift and 1.7 ratio rocker arms. My buddy just found all 8 of his intake guides worn out, with 6k on the motor...Clearly a machining issue, if you ask me.
Don't forget about the thousands of LSx motors out there with stock powdered metal guides and ~.600" lift aftermarket cams, that aren't prematurely wearing out the guides.
The material and length are not the smoking gun here.
Don't forget about the thousands of LSx motors out there with stock powdered metal guides and ~.600" lift aftermarket cams, that aren't prematurely wearing out the guides.
The material and length are not the smoking gun here.
02-25-2014, 03:39 PM
#7
Pro
They aren't the same heads as the LS3...different casting method, different alloy, different valve materials, different port geometry, different valve seat material...and possibly a different manufacturer or different assembly line.
02-25-2014, 06:47 PM
#8
Team Owner
DH
02-25-2014, 06:55 PM
#9
Burning Brakes
Member Since: Mar 2010
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I do remember during one of my conversations with Richard about spec on the Brodix heads he was doing for me, that he loved their heads EXCEPT for their valve guides, which he removes and replaces with his choice.
