What is the preferred valve guide material? Silicon-bronze, manganese-bronze, Moldstar alloys, etc.? Getting some guides and trying to decide on the material.
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What is the preferred valve guide material? Silicon-bronze, manganese-bronze, Moldstar alloys, etc.? Getting some guides and trying to decide on the material.
Whatever the OEM uses...?Quote:
Originally Posted by rsportvolvo
;)
I'm polishing a turd, so to speak, so I need to maximize every area available!!
Whichever costs the most.
My understanding is the silicon bronze is a little softer than the manganese bronze. The manganese bronze is used in applications where higher temperatures are expected. I believe most OEM guides are iron (pretty sure that's what my Honda is). I'm sure there are special alloys (I've personally never heard of Moldstar) for more "serious" applications, but I can't imagine those being required for a club racer build. I think either bronze would be a good choice.
My hope is that the manganese bronze, Moldstar, etc. valve guide material will transfer more heat out of the combustion chamber. That should give me a bit more margin for detonation and possible the ability to advance the timing a degree or so more.
On a low compression engine you want to keep as much heat in the combustion chamber as possible to make power. Chukc
That makes sense.Quote:
Originally Posted by chuck baader
I'm thinking more along the line of detonation prevention as the exhaust valve is a typical hot spot and better cooling the valve will help prevent detonation. Does this jive with actual numbers?
trasnfering heat to the valve, and valve guide is not a good idea. Measures are usually taken to prevent any heat getting to the valves (coatings and such that are IT illegal).
Bronze is a great conductor of heat and elctricity, however it also has a much greater thermal expansion coeficent than steel.. so if you are planning on heat soaking the valve guide via the valve to your head, which will already be heat soaked from the combustion process.
You will recive greater anti detoniation charcteristics from running higher octane fuels and or different spark plug heat ranges if you want to run alot of spark advance.
The goal is to cool the exhaust valve face. That heat is transferred via the valve stem, the valve seat and the valve guide. Using the stem and guide is quite common as many cars have sodium filled exhaust valves.Quote:
Originally Posted by quadzjr
The thermal expansion is remedied with proper clearances.
Higher octane fuel is a given. That is step zero. In order to squeeze more power out of the engine I'm looking at other ITCS legal options.
all to familiar with teh sodium filled and other designs. Maybe I never thought about the heat transfer from the face of the valve-> to the vavle stem-> through the guide-> to the head. Is there enough contact and heat dispation characteristics to even think about it? From the outside I would assume that we know heat transfer would exist but compared to other things it would be minimal. I would think that the valve heat dispations would happen at a much greater rate, jsut above the guide and seal via the oil. I could be wrong :shrug:
Not sure if the gains are much, if even measurable. But it's all we have to play with in IT. I figure in IT trim every bit helps.
everything is measurable, that hard part is figuring out how.Quote:
Originally Posted by rsportvolvo
the best way to find if it makes any difference is to have two heads, and dyno both.