Quote:
Originally Posted by Tony Cavotta
Has anyone ever heard or relieved 4 banger like we would V8
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Tony, expounding on what Mr. Clarke said in post #2, ...the top of the valve seat is flush with the deck surface of the cylinder case (block), so there is nothing to be gained by undercutting, however there are two or three things that I feel can help in performance though;
#1, The top edge of the bore can be radiused slightly on the edges where the fire ring is not touching. This will aide slightly in transitional air flow.
#2, while it may seem counterproductive because it slightly lowers the compression ratio, often times the volumetric efficiency can be increased if the valve is unshrouded on the backside by opening up the valve clearance area in the cylinder head.
#3, having a multi-angle seat machined (3-angle, 5-angle, infinite-angle) allows the gasses to better flow over the sharp edge of a 45° angle. Ultimately, look for ways to allow the incoming and egressing air/gas to happen more efficiently.