Sportsman 11 Porting

[wilson1970]

Any good advice on porting Sportman 11 Iron Heads for 355 street engine?Thanks

[Carnut1]

Google search Sportsman 2's porting. An older thread I did. Heads ran well, I would do them differently now. Thanks, Charlie

[mag2555]

Street usage does not tell us much these days!
How much does the car weigh?
Auto or man Trans?
What rear gears?
How much hp would you be happy with?
How much rpm Can you live with?

[Frankshaft]

For a 355, I would stick to the basics. streamline guide bosses, they are huge, roll short turn, and I would install 2.055 intakes for no other reason to improve the stock valve job. Its pretty crappy. It reminds me of how gm did it back in the day. Big 70 throat cut, minimal bottom angle, and terrible top cut to chamber transition. Doing something like a 38-45-60-75 intake, with a nice top cut to chamber transition, keep throat at small size for 2.055 valve, 88-89%. Exhaust, a 39-45-with a radius under the seat into the bowl. About 86% throat. To get that intake seat, you will need to install the bigger valve to gain back the material, because that aggressive 70 degree cut removed it. Or, a 40-50-65-75 intake seat with the 2.02, size throat about 91%. There should be material to get all the angles in with the 2.02 valve, 50 degree seat. Only issue, your current valves, may not have enough margin to change the angle from 45 to 50. The rest of the intake port doesn't need to be touched. It has a fairly generous cross section, and nice complementing areas, pushrod pinch is also about 2.3 untouched, leave it alone. All the gain for your application will be in the bowl, short turn, valve job and chamber. The exhaust port is plenty big as well. Same mods, guide boss, bowl, short turn, valve job and chamber. The good news, is less is more here.