I am putting a '70 455 (non smog) intake to a '73 455 (smog)engine. Each of the heads has a large exhaust crossover port, with two holes in each port. They look to be about 11/16" to 3/4". Does anyone know exactly what size these holes are? There are eight smaller exhaust holes (four on each side) above the intake ports that look to be about 5/16". What exact size are these holes Thanks, Kevin
18mm on the crossovers, got freeze plugs @ NAPA and tapped them in my motor. I had to sink them deep to get a good bite, but they are holding, so far. No info on the others but your intake should cover them.
the other eight holes are for the egr system....they are a straight shot into the combusiton chamber and need to be plugged...I don't think the 70 intake will cover them and I don't know the size...do a search here for A.I.R. or E.G.R. , pretty sure there are more threads on this issue. later Tim
JB weld I used jb weld to plug the little holes in the heads because my intake didnt cover them either. It has worked perfect so far, about 5,000miles and a couple of track runs. will
I used JB Weld to plug a Ford 400-M crossover and it worked fine. On the 455 Buicks round crossovers I machined a piece of hot rolled steel to a loose, but touching fit, crumpled up a piece of paper towel to stop the JB from going too far, smeared JB over the steel dowel and into the crossover holes, slid the steel dowel in and 41,000 miles later it's doing fine. You will want to use a late style gasket with an early style intake to hide the large square port that will be exposed if you use an early style gasket on the later heads. I think I said that right. :grin: I run an Offy medium riser dual quad on one car and this system works well. The Offy's gasket surfaces are cast/machined the same as the early stock intakes. Reason for using hot rolled steel - the most commonly found type - is that it machines very rough in most cases and that helps the JB to get a "tooth." No reason cold rolled wouldn't work, make a point to give it a rough finish when turning it.
Friend of mine had a 73 motor and put a 430 intake on it. He used 18.03mm freeze plugs (Advance Auto) in the crossover holes. He used epoxy to fill in the rest of the square hole. For the AIR holes he drove in an aluminum rod in each. He recently sold the motor. He had no problems with it.
