Porting a 226 manifold

hey Marty,can u chime in here?

 Port as per Bill, and polish the exhaust. Don't polish intake ports.

U can port and polish the intakes just don't polish them as smooth, if u leave them a little rougher they mix the air and fuel better. If u polish the exhaust super smooth the exhaust leaves the cylinder faster and easier hence more hp. And if u port match intake and exhaust it will flow air without resistance. I did my own with a die grinder and carbides and small flapper wheels.

I have a brand new d17 manifold that I hope to improve flow through. I know I'm capable of doing the work and realize it's very time consuming. Does anyone know for a shop that does this kinda work and what they might charge as I might just want to have them do it right and flow test it. Thanks

My first step is to blast it clean. Why? Because my next step is to start welding. I'm going to weld where the intake neck meets the manifold and fill those corners. Then I'm going to knock some holes in the back side on each side of the carb neck in the runners to gain better access to the inside corners.

Then I'm going to drill a hole dead center in the top of the manifold above the carb and tap threads on it. This will allow me to put a bolt or stid in and be a mechanical anchor or lock for an epoxy divider later on. I'm also going to drill where the runners go into the head, on the front of the manifold there's a little round point cast on each side, tap it. This also allows for a bolt for a positive lock for some epoxy later.



Now I'm ready to grind. I'm going to grind the carb neck to manifold corner and reach in my access holes and finish the back side of the corner I'm going to get real aggressive on that corner but I welded on the outside of the manifold so I have more material to work with and I'm going to build the biggest radius I can in that corner. Then when it's done I'm going to build a wedge in the center of the top, above the carb put of epoxy, put a bolt in that drilled and tapped hole and build a divider wedge to fill the space and keep one side( front or back) from robbing the other on intake overlap.

Now I'm going to grind the bottom of the round runner that mates to the head, I'm going to cut a teardrop shape on each side so I wind up with a flat bottom of a D shaped port that transitions to round where it meets the head. I'm going to again make the biggest radius I can on the corner. Then I'm going to put some bolts in and fill the top with epoxy to hold the air from expansion, and keep it held on the floor.

Air hates to expand, air hates to turn corners. Filling the right areas and cutting the largest radiuses is important, the size however isn't so important.

If I take a bone stock manifold and put it on a fixture i are on the flow bench and radius the carb inlet, draw 28" water depression on it, each side of the manifold will flow about 115 cfm. With a quick and dirty radius on the top of the carb neck, 140 cfm. With welding and epoxy work, 180 cfm. If I really work and build a complete new carb neck, weld the back side of the runners and really work hard, 225 cfm, through a stock appearing manifold.