Why not 2.055" Int. Valves???
Why not 2.055" Int. Valves??? Im new to the LS1 scene, and was wondering if there was a reason that more people are using the 2.02" instead of a 2.055". I would think that the LS1s would work better with the larger Intake valve.
With stock cubic inches, you lose velocity with the 2.055 valves as compared to the 2.02's. With lower velocity, it won't charge the cylinders as well hence making less HP.
Launching!
Joined: Dec 2003
Posts: 251
Likes: 2
From: Portland OR
Valve size is a tradeoff. Larger valve sizes mean larger "curtain area" - the area between the valve and the valve seat, through which the air must flow. Curtain area is particularly important at low valve lift. On the other hand, the bigger the valve, the closer the edge of the valve is to the cylinder wall - an effect called "shrouding", which limits the air path near the outside of the cylinder. The optimum valve size will therefore depend on bore size, which is smaller at 3.9 than the Gen 1 & 2 small block Chevy at 4.0+. It will also depend on port shape - port shapes which encourage air flow toward the inside of the bore will be less subject to shrouding. Larger bore motors will obviously respond better to larger valves, due to less shrouding. In practice, standard bore LSx motors seem to make very good power with a range of intake valves from 2.0 to 2.055, depending on the head porter ...
TECH Resident
Joined: Apr 2003
Posts: 791
Likes: 0
From: Tulsa, Ok
i think jay at absolut is putting in 2.04's in the stock seat. he was using 2.02 but found the 2.04 made a little more power. and since you don't have to install a new seat, the cost dosn't go up a whole bunch.
Launching!
Joined: Dec 2003
Posts: 251
Likes: 2
From: Portland OR
Actually, it isn't usually valve size which determines port velocity, because the smallest area of the port is usually upstream from the valve seat, before the valve guide. BTW, MTI has used 2.055 intakes for their standard stage 2 heads for years, and their heads have a very good reputation.
