Quick question on valve sizing
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From: Sneads Ferry, NC
Quick question on valve sizing Like the title says..while everything was at the machine shop I had my guy re-work my 243's. New guides, valve job, 58cc chambers etc.
Well I had originally wanted 2.02 1.57. He insisted that I go 2.02 1.60 saying it's what he always does. I went along with it and told him to blend the bowls to match. Now I'm seeing that no one else does this unless there is a stupidly large intake valve to match.
I realize bigger isn't always better, so did I just **** up my driveability going so large on the exhaust valve?
Also on a side note, do you think I'm leaving something on the table going with a 228r vice a larger cam? Strictly DD, drive-ability focused, fun car.
Thanks guys.
Well I had originally wanted 2.02 1.57. He insisted that I go 2.02 1.60 saying it's what he always does. I went along with it and told him to blend the bowls to match. Now I'm seeing that no one else does this unless there is a stupidly large intake valve to match.
I realize bigger isn't always better, so did I just **** up my driveability going so large on the exhaust valve?
Also on a side note, do you think I'm leaving something on the table going with a 228r vice a larger cam? Strictly DD, drive-ability focused, fun car.
Thanks guys.
Most shops go with the smaller exhaust valve to help keep velocity up so you can evacuate the cylinder quickly. AFR uses a larger valve in conjunction with a larger port to enhance the I/E efficiency of the head. This makes them more sensitive to header primary size than other heads. Slapping a larger valve on a stock head may not do much.
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From: Sneads Ferry, NC
Hmmm. Well it's a 1.60 with just a bowl blend, stock runner, going into swap specific 1 7/8 headers with a 3" collector.
So although I may not see performance gains I won't see a decrease in any numbers? I know over-enlargement of anything on the intake side usually means a decrease in torque..more or less
So although I may not see performance gains I won't see a decrease in any numbers? I know over-enlargement of anything on the intake side usually means a decrease in torque..more or less
I did basically the same thing to the heads in my car. I put in 2.02"/1.60" valves, opened the throats up, and blended it all in. It doesn't hurt anything to have a larger exhaust valve with such a small intake valve. In my opinion, it's better.
Most of the exhaust gas is evacuated before the piston reaches BDC, during what's called "the blowdown phase". The exhaust valve is cracked open as the piston is still moving down on the power stroke, so there is still a tremendous amount of pressure in the cylinder and it needs more curtain area to allow it to get out. A larger valve and a quick opening ramp help achieve this.
Most of the exhaust gas is evacuated before the piston reaches BDC, during what's called "the blowdown phase". The exhaust valve is cracked open as the piston is still moving down on the power stroke, so there is still a tremendous amount of pressure in the cylinder and it needs more curtain area to allow it to get out. A larger valve and a quick opening ramp help achieve this.
