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Old 07-02-2021, 11:29 AM   #25
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Originally Posted by blsfrs View Post
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Valve guides can be generally classified into two groups: cast iron and manganese bronze, which covers a wide range of applications.
Cast iron guides are used mostly by OEMs due to its wear characteristics that result in longevity for high mileage applications. Cast iron is used with chrome valve stem applications as well. Cast iron cannot be used with stainless steel because of its tendency to gall.
Thatís why high performance applications do not warrant the use of cast guides due to the fact the material canít handle the high loads associated with higher spring pressures. Under high stress, cast iron guides tend to crack and fracture, which can result in engine failure altogether. Cast iron is inexpensive and works best with daily drivers and high mileage applications.

For any kind of performance application, the choice is manganese bronze. The way to pronounce this correctly is MAN-GA-NESE. I often hear this as magnesium, which is not correct. Manganese bronze is ideal for performance because it is more compatible with titanium and stainless steel.

Just for reference.
Granted 99% of my engine building experience comes from motorcycles/atv's, I know of at least one instance where I used SS valves with OEM iron guides. It was a heavily modified air cooled engine. It was in the raw, no coating on the stem. Never had any issues

We liked to use copper beryllium seats with either bronze or copper guides depending on application for built engines.
"Experience is the hardest kind of teacher. It gives you the test first and the lesson afterward." -Oscar Wilde.
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