Bronze Valve guides

With the Addition of Ethanol in Canadian fuels now prevalent in most fuel stations, I was wondering if there are problems using the bronze valve guides. I am working on my head and am thinking of going back to the Cast Iron valve guides if the bronze units will cause problems. Does anyone have experience or input on using these for street use? I have heard from some sources that the lubricants that use to be used in fuels (leaded fuel) are no longer present and the bronze guides gall because of lack of lubricants and the Ethanol additives used in the fuel.

Interesting question. I know bronze is used as a bearing or bushing material so it must have good wear properties. Regarding fuel, I was told that using hardened valve seats was the way to go since unleaded fuel is all that there is, but what do I know? The ethanol question is good and I would like to know as well.

CanukNortonNut said:

With the Addition of Ethanol in Canadian fuels now prevalent in most fuel stations, I was wondering if there are problems using the bronze valve guides. I am working on my head and am thinking of going back to the Cast Iron valve guides if the bronze units will cause problems. Does anyone have experience or input on using these for street use?

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The ethanol additive won't have any adverse effects regarding your valve guides. In fact, bronze guides made of modern, aircraft-engine spec materials such als "Colsibro" are much better than cast iron ones, they offer not only less friction to the valve stems and thus better wear characteristics, but also expand under heat similar to the aluminium of the cylinder head they are seated in, and thus won't tend to come loose prematurely. They also allow for tighter tolerances, which make the rubber oil seal caps superfluous.

CanukNortonNut said:

I have heard from some sources that the lubricants that use to be used in fuels (leaded fuel) are no longer present and the bronze guides gall because of lack of lubricants and the Ethanol additives used in the fuel.

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Unleaded fuel does lack the "lube-coating" effect the soft valve seats (not the valve guides!) of yesteryear benefitted from. With appropriate hard valve seats, there is no problem with modern fuels.
The addition of ethanol (alcohol) does also has some advantages - it reduces premature ignition and thus "pinging", and reduces combustion chamber temperatures somewhat. Pure methanol-fed (another type of alcohol) dirt-tracker engines can thus make use of diesel-like compression ratios of up to 22:1 w/o problems....
The disatvantages of ethanol additives per se are negligible - they make the fuel slightly more corrosive and provide substantially less combustion energy than petrol. However, a, say, 10% ethanol addition will not lead to any significantly or even noticeably adverse effects to a road-going motorcycle's engine. Don't worry - be happy!

brittwin said:

In fact, bronze guides made of modern, aircraft-engine spec materials such als "Colsibro" are much better than cast iron ones.

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Are guides made of this material available for the Norton, or would you find the stock and have them made?

brittwin said:

With appropriate hard valve seats, there is no problem with modern fuels.

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Did Norton ever use hardened valve seats?

Just curious about these things Thanks!

All Norton alloy heads have hardened seats as std as do Triumph and BSA, there is no need for new seats unless they are damaged.

caspermj said:

Are guides made of this material available for the Norton, or would you find the stock and have them made?

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Most cylinder head shops have them or can supply and fit "ROWE" guides - these are excellent ones made of silicon-bronze, very close to "Colsibro". They come in various sizes in case your head guide seats need to be reamed and thus become oversized. When the head shop replaces the worn seats, it is a must to have the valve seats re-ground for proper guide-seat alignment. If the seats are worn-out or have sunken too deeply into the head due to multiple re-grinds, it is a good idea to replace them too. And, perhaps, to get new valves, such as the "Nucleus" or "Black Diamond" types, which are a one-piece job (stem & dish) and approx. 5-10% lighter than stock......

caspermj said:

Did Norton ever use hardened valve seats?

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To my knowledge, hard steel valve seats (some made of sintered material) were quite common from the early 70's on throughout the whole automotive industry.