A local friend of mine mentioned he had some bigger valves for a G head. He said they were the largest ones that will work with stock seats. But I can't wrap my head around how a slightly larger diameter valve will flow better if the "hole" behind the valve is the same size. Can someone explain this to me? It's probably simple but it's something I've never messed with. The head currently has stock valves that are backcut per Gary Ds instructions.
The seat can be cut back a bit with +1mm valves to allow a slight improvement.
But if the seat isn't modified there is really no gain right?
I believe the stock seat is cut larger during the valve job to accommodate for the bigger valve, which leads to a higher available area for air to flow around the valve. Correct me if I'm wrong though.
Last edited by jefo; 09-28-2015 at 05:48 AM.
If shrouding is increased, a larger valve can hurt flow. If no other improvements are made, don't expect much. ..
Mike
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Does anyone ever install different seats in 8 valve heads?
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