Routing exhaust through cross members?

[SonomaZ]

So I took redss86/Joe's advice and picked up a 4-1/2" bi-metal hole saw. Wasn't sure how well my 18V cordless DeWalt would handle it. I've never hole-sawed anything that large. Shouldn't have been concerned, it powered right through it. Thanks Joe, worked great!

This was on a 2" X 3" X .120 wall reinforcement tube. Clearance for round 3-1/2" single side exhaust; outlet thru-body in front of rear tire. Clearance ring/donut is 4-1/2" OD, 1/4" wall, so 4" ID. I have two more of these to do in the transmission crossmember for the 3" header collector extensions. I might start with a 1/2" smaller ring for those.

The key (like most good outcomes) was in the preparation: measure twice, cut once. Carefully measured and scribed out the pilot hole location on both sides of square tube. Drill pilot from each side and run hole saw through each wall separately from each side. I made it so the bottom of the exhaust pass-thru donut sits flush with the bottom of the square tube so as not to give up ground clearance. (Bottom of the frame sits 4" off the ground.)


The "web" that's left between the two walls was cut out in the following pics so that the donut would fit and sit flush.