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  1. #1
    Join Date
    Aug 2004
    Location
    Greenville, IL
    Posts
    261
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    Routing exhaust through cross members?

    I am finally getting back to working on my Monte again. I have rebuilt the perimeter frame out of 2x4x0.125 wall tubing. I have a cross member at about the middle of the frame for my truck arms. Then I have braces going forward basically from the truck arm mounts to the front torque boxes on the frame (see attached pics). I am thinking I want to some how route the exhaust through these by welding in some round tubing. I am just a little unsure on what size/ thickness to use. I am figuring on running oval exhaust, but is still think I am going to want the extra clearance. So if it goes through the braces, it will give me plenty of room. The exhaust is going to have to exit in front of the rear wheels, because it would be impossible to get it over the axle with the truck arms, panhard bar, and gas tank setup.

    Thanks for any and all suggestions. I was thinking about using something like 4"x0.250 wall? Not sure what I need to maintain adequate strength?

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    Joe Marti
    86 Monte Carlo SS build thread
    65 Mustang Coupe
    00 WS6 Trans Am (wife's car)
    15 Silverado LTZ 4x4

  2. #2
    Join Date
    Aug 2016
    Location
    Waconia, MN
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    102
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    Same only different... and a How-To? question

    I hope I'm not breaking a cardinal rule by bringing up a 2+ y/o thread...

    I have something of an answer, if not for the OP, then whoever may get here by searching as I did.

    I'll be using these for my build: https://www.cachassisworks.com/p-27-...-x-2-long.aspx
    Seemed an expedient way to go versus hunting for the proper size and wall section in pipe and then having to slice and dice. 4" ID X .250 wall mild steel. I'll be welding these to a 2" X 3" X .120 fabricated transmission crossmember.

    So the question is: How to go about cutting a nice matching radius into my 2X3's so I can (hopefully) weld them cleanly and not have it look like I hacked them out with a stone axe?
    Any and all suggestions welcome.

    Thanks.

  3. #3
    Join Date
    Aug 2004
    Location
    Greenville, IL
    Posts
    261
    Country Flag: United States
    I never knew there was any kind of rule about bringing up old posts.

    If you are keeping them round, I would try to find a hole saw. Maybe go a size small and use a die grinder to get the final fit. I used a plasma torch, and finished with the die grinder, but I made mine oval so I have optimal ground clearance. I plan to use oval exhaust tubing also. When I cut mine I cut three sides of the cross-member and cut the pass through in. Then cut the final side. This way the cut tube didn't move or flex. I have yet to completely finished mine. I still have some extra bracing to do, and I still have to put two through my forward braces. I think I actually ended up using some 4.25x.250 Dom tube. Hope this helps.

    Here is the exact same post I made in the suspension section. I got more response there than here.
    http://https://www.pro-touring.com/t...-cross-members
    Joe Marti
    86 Monte Carlo SS build thread
    65 Mustang Coupe
    00 WS6 Trans Am (wife's car)
    15 Silverado LTZ 4x4

  4. #4
    Join Date
    Aug 2016
    Location
    Waconia, MN
    Posts
    102
    Country Flag: United States
    There likely isn't a rule about the old post thing... I just know some forums frown upon it. This place seems pretty laid back about stuff like that, which is nice.

    Thanks for that link. You and your plasma torch do nice work, looks good. I may have to go oval as well or I'll have to offset the clearance circles up towards the floor since I don't want to give up 3/4" ground clearance in those areas. I'll be cutting floor anyway, so a little more isn't going to hurt.

  5. #5
    Join Date
    Jun 2001
    Location
    Orlando, FL
    Posts
    10,875
    Country Flag: United States
    We prefer folks use search, and that implies surfacing older threads. It's all good.
    John Parsons



    II Much Fabrication's Blog -- New products, Fabrication sequences, etc.

    II Much Fabrication's Current Build -- LS9-powered 69 Camaro

  6. #6
    Join Date
    Aug 2004
    Location
    Greenville, IL
    Posts
    261
    Country Flag: United States
    Quote Originally Posted by SonomaZ View Post
    There likely isn't a rule about the old post thing... I just know some forums frown upon it. This place seems pretty laid back about stuff like that, which is nice.

    Thanks for that link. You and your plasma torch do nice work, looks good. I may have to go oval as well or I'll have to offset the clearance circles up towards the floor since I don't want to give up 3/4" ground clearance in those areas. I'll be cutting floor anyway, so a little more isn't going to hurt.
    Thank you, mine are actually offset towards the bottom. But I have them up as close to the floor as I feel comfortable. I have been doing a lot of fab work on my car. Here is my build post if you are interested.

    https://www.pro-touring.com/threads/...-super-project
    Joe Marti
    86 Monte Carlo SS build thread
    65 Mustang Coupe
    00 WS6 Trans Am (wife's car)
    15 Silverado LTZ 4x4

  7. #7
    Join Date
    Mar 2012
    Location
    Marianna, FL
    Posts
    394
    Country Flag: United States
    Quote Originally Posted by redss86 View Post
    I am finally getting back to working on my Monte again. I have rebuilt the perimeter frame out of 2x4x0.125 wall tubing. I have a cross member at about the middle of the frame for my truck arms. Then I have braces going forward basically from the truck arm mounts to the front torque boxes on the frame (see attached pics). I am thinking I want to some how route the exhaust through these by welding in some round tubing. I am just a little unsure on what size/ thickness to use. I am figuring on running oval exhaust, but is still think I am going to want the extra clearance. So if it goes through the braces, it will give me plenty of room. The exhaust is going to have to exit in front of the rear wheels, because it would be impossible to get it over the axle with the truck arms, panhard bar, and gas tank setup.

    Thanks for any and all suggestions. I was thinking about using something like 4"x0.250 wall? Not sure what I need to maintain adequate strength?

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    You could always have the pass-throughs CNC Plasma or Water Jet cut and lap them over the existing tubing. I ran into the same issue on my trans cross member and ended up notching it to allow the exhaust space. To compensate for the notches I added some additional material to the top, if that makes sense.

  8. #8
    Join Date
    Aug 2016
    Location
    Waconia, MN
    Posts
    102
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    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.)

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    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.

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  9. #9
    Join Date
    May 2019
    Location
    Pensacola,Fl.
    Posts
    26
    I have those same pieces from Chassisworks....Along with the whole rear clip.

  10. #10
    Join Date
    May 2013
    Location
    San Diego, CA
    Posts
    219
    Country Flag: United States
    Art Morrison does something similar with their frames