Valve Replacement Questions

MrBlvd

Registered User
I'm in the process of building up a set of replacement heads for my car and need some guidence on the valves. The heads will be ported/polished and have a 3 or 5 angle valve job. I've read a lot of threads discussing the use of larger valves but have not found an answer to the following:

1. What is the largest exhaust valve you can use w/o having to install new seats? Is this worth messing with or should you just go with the 1.6 valve and new seats? (I do not plan to install larger intake valves)

2. Generally speaking, what effect does having the ratio of the exhaust valve / intake valve too high have? Stock = 1.46/1.78 = .820, Coy Miller Stage 1 = 1.6/1.78 = .899, coy Miller Stage 2 = 1.625/1.85 = .878, I've also come accross 1.56/1.84 = .847 and 1.6/1.84 .869 in the forums.

My current "hope" is that a 1.56 exhaust valve will work with a remachined stock seat and provide a ratio of .876.

3. When using the "SBC" valves ( I assume this means small block Chevrolet), are the valve stem lengths the same as the stock SC valves? If not, are they taller or shorter? How do you accomodate the different length? If shorter, I'm assuming this is where the use of "shims" comes into play.

Obviously, I still have a lot to learn ... any insights or guidence would be appreciated.

I probably should have figured this valve stuff out before I "cleaned up" my spare set of valves.
 

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