The stock valve job can be improved on Vortec heads. Mondello got more cfm at high lift after performing his own 35/45/60-degree valve job and 75-degree throat cut, but this sacrificed some flow at lower lift (compare: Intake tests 1 and 3).The stock valve job can be improved on Vortec heads. Mondello got more cfm at high lift af Mondello scribes lines at the widest section of the ports. Look closely and you'll see the scribe mark on the top of the port (bottom of photo) is much higher. This is where Mondello raises the roof to a Fel-Pro (PN 1206) gasket's dimension.Mondello scribes lines at the widest section of the ports. Look closely and you'll see the The intake valve on the left has a 21-degree back cut to improve airflow at low lift. The exhaust gets a 22-degree back cut.The intake valve on the left has a 21-degree back cut to improve airflow at low lift. The Getting the corner radius correct is one of the hardest parts of porting. Mondello uses a tube with a radius equal to the gasket (most gasket manufacturers can supply this info) to scribe and check the marks.Getting the corner radius correct is one of the hardest parts of porting. Mondello uses a Mondello starts on the sides of the valve guide boss bringing them into the mark he's made using a special tool he developed and sells. Once the sides of the guide are done, Mondello begins to teardrop the guide, in the direction of the port to aid airflow around it.Mondello starts on the sides of the valve guide boss bringing them into the mark he's made Blend all high and low spots in the chambers. Make sure to put some old valves in the pockets at all times when working the chambers, and always scribe the gasket opening onto the cylinder head so you don't go too far.Blend all high and low spots in the chambers. Make sure to put some old valves in the pock You'll need a set of stones to finish your porting and a dressing tool to shape the stones. Mondello shapes a large stone to smooth the big radii in the chamber. This helps maintain the proper combustion chamber shape while still smoothing the casting. All flat surfaces on the chamber get smoothed with a sanding disc. The final polish can be done with a flapper.You'll need a set of stones to finish your porting and a dressing tool to shape the stones Be sure to deburr the area around the spark plug hole after polishing. EXHAUST PORT TESTS Exhaust Lift 0.10 0.20 0.30 0.40 0.50 0.60 0.70 Test 1 45 46 95 135 153 157 156 158 Test 2 4854 100 143 155 156 157 158 Test 3 4452 103 137 151 153 153 154 Test 4 4754 108 142 153 152 152 152 Test 5 55 49 99 139 159 169 173 175 Test 6 104 144 164 171 174 176 Test 7 99 141 162 170 174 177 Test 8 114 147 164 170 172 174 Test 9 110 151 174 187 192 195 Test 10 98 145 167 183 190 192 Once you've got the intake ports done, you can clean up and polish the exhaust. These ports are short and easy to work on, but take your time and don't enlarge them. Just straighten them out and clean them up.Once you've got the intake ports done, you can clean up and polish the exhaust. These port On the left is the port for Test 8/4 and right is Test 7/3. You can see the finished guide boss and smooth port walls on Test 8/4. Mondello blended the port opening on Test 7/3, performing what most people refer to as a port-match, but it's not actually matched to anything right now; it's just smooth and straight.On the left is the port for Test 8/4 and right is Test 7/3. You can see the finished guide This is the most basic porting job (see: Intake Test 5/1). After the valve job is done, we blended the throat cut into the bowl. It's plain to see where high and low spots are in this photo. We finished each step with a stone to remove the rough marks left behind by the carbide cutter.This is the most basic porting job (see: Intake Test 5/1). After the valve job is done, we Next, we blended the bowl into one smooth surface down to the valve guide boss (see: Intake Test 6/2). We did not touch the short-side radius (the area on the floor of the port leading to the valve seat) yet, except to clean up any rough casting flaws or machining ridges left behind.Next, we blended the bowl into one smooth surface down to the valve guide boss (see: Intak Here's a fully blended intake bowl and valve guide boss (see: Intake Test 7/3). Properly shaping the valve guide boss is crucial to good airflow and takes lots of patience.Here's a fully blended intake bowl and valve guide boss (see: Intake Test 7/3). Properly s The scribe marks indicate where Mondello plans to open the chamber up to match the head gasket. Note the cut next to the intake valve seat Mondello made on his Serdi valve machine. It ensures that the largest portion of the chamber is centered on the valve, and it smoothes the transition to the 37-degree seat cut.The scribe marks indicate where Mondello plans to open the chamber up to match the head ga Mondello offers all the porting supplies you could ever need. He also recommends and uses abrasives and cross-buffs from Standard Abrasives, for which he is also a distributor.Mondello offers all the porting supplies you could ever need. He also recommends and uses SOURCES SCOGGIN-DICKEY CHEVROLET (Source for GMPP parts) 5901 Spur 327, Dept. SC Lubbock, TX 79424 Mondello Technical School 830 21st St. Paso Robles CA 93446 Standard Abrasives 4201 Guardian St. Simi Valley CA 93063 Enjoyed this Post? Subscribe to our RSS Feed, or use your favorite social media to recommend us to friends and colleagues!
