Greg Good Cylinder Heads
Enthusiast
I finished porting my first set of Gen 3 heads last week. They are definitely better than Gen 2's. DC gave the Viper a lot more flow. The port shapes are more refined and flow better than Gen 1 and 2 heads. Stock, out of the box, the intake port hit 285 cfm, and the exhaust just made it to 200 cfm. These numbers are as good as most garden variety ported Gen 2 heads. For comparison, a stock Gen 2 head flows slightly over 240 cfm on the intake and 170 cfm on the exhaust. That is +45 cfm on the intake and + 30 cfm on the exhaust over a Gen 2. Part of the reason for the increased intake flow of the Gen 3 is the larger 2.00" intake valve.
The shape of the intake runner is pretty straight forward, without any gimmicks. The intake port has the same entrance as the Gen 2 head. But, further down the port at the short side radius the shape is a lot different. There isn't a lot of port bias like on the Gen 2 head. The port did not really need any major changes in shape, just the usual tweaking that head porters like to do. The floor over the short side has a funny "stair step" in it. I left it alone and lightly blended it with a polishing roll.
The exhaust port is more generous in size than a Gen 2. It doesn't need nearly as metal removed from it to make it flow.
The only thing I did to the combustion chambers was remove a slight amount of material in the right place to help with wet flow. I liked the shape and the general lack of valve shrouding so I did not need to take much material out. The valve seats and the chamber match more closely and it is easier to blend them in. Those who have ported Viper heads before know how hard that area can be to clean up. The stock chambers are 78 cc's.
As this was my first set of Gen 3 heads I played it safe, did not remove much material, and did not have any problems hitting water. The place where I did the most grinding was in the pushrod section of the intake port, which has no water around it. I also left the venturii under the valve seats small to promote good mid lift flow. This set of heads at .600" lift hit 320 cfm on the intake and 225 cfm on the exhaust. Both ports had extremely good mid lift flow. The intake port hit 300 cfm by .500" lift and 313 at .550", which is good usable flow for a street Viper, unlike flow at .700" lift which looks good on paper, but does nothing for a car with only .575" lift. The exhaust hit 220 cfm by .500". I know there is more flow left in these heads. I would say the intakes have the potential to go 325-330 cfm and the exhausts about 235 cfm with more work.
The only gripe I have with this first set is that the valve seats are super hard and liked to chatter when machined with a Serdi cutter. It was necessary to touch up the seats with a Kwik Way grinder.
Greg Good
The shape of the intake runner is pretty straight forward, without any gimmicks. The intake port has the same entrance as the Gen 2 head. But, further down the port at the short side radius the shape is a lot different. There isn't a lot of port bias like on the Gen 2 head. The port did not really need any major changes in shape, just the usual tweaking that head porters like to do. The floor over the short side has a funny "stair step" in it. I left it alone and lightly blended it with a polishing roll.
The exhaust port is more generous in size than a Gen 2. It doesn't need nearly as metal removed from it to make it flow.
The only thing I did to the combustion chambers was remove a slight amount of material in the right place to help with wet flow. I liked the shape and the general lack of valve shrouding so I did not need to take much material out. The valve seats and the chamber match more closely and it is easier to blend them in. Those who have ported Viper heads before know how hard that area can be to clean up. The stock chambers are 78 cc's.
As this was my first set of Gen 3 heads I played it safe, did not remove much material, and did not have any problems hitting water. The place where I did the most grinding was in the pushrod section of the intake port, which has no water around it. I also left the venturii under the valve seats small to promote good mid lift flow. This set of heads at .600" lift hit 320 cfm on the intake and 225 cfm on the exhaust. Both ports had extremely good mid lift flow. The intake port hit 300 cfm by .500" lift and 313 at .550", which is good usable flow for a street Viper, unlike flow at .700" lift which looks good on paper, but does nothing for a car with only .575" lift. The exhaust hit 220 cfm by .500". I know there is more flow left in these heads. I would say the intakes have the potential to go 325-330 cfm and the exhausts about 235 cfm with more work.
The only gripe I have with this first set is that the valve seats are super hard and liked to chatter when machined with a Serdi cutter. It was necessary to touch up the seats with a Kwik Way grinder.
Greg Good
Great work!
