I'm looking for a way to re route my exhaust on my CJ3a. Right now I have the V6 exhaust inside the frame rails and the trans. and T.C. are tucked up pretty good. The sm420 won't hang down any lower than the T.C. But the sm420 bolts right to the B.O.P. bellhousing were I now have an adaptor and the cross over passenger side exhaust pipe.
http://i17.photobucket.com/albums/b89/willysworker/Red%20Dog/driversideviewundercarriage.jpg
http://i17.photobucket.com/albums/b89/willysworker/Red%20Dog/driversside2undercarriage.jpg
http://i17.photobucket.com/albums/b89/willysworker/Red%20Dog/passengersidefrtundercarriage.jpg crossover pipe location will be lost
http://i17.photobucket.com/albums/b89/willysworker/Red%20Dog/passengersiderearundercarriage.jpg
http://i17.photobucket.com/albums/b89/willysworker/Red%20Dog/bellypanfronttoback2.jpg front to back view
http://i17.photobucket.com/albums/b89/willysworker/Red%20Dog/gastankbatterybox3.jpg
http://i17.photobucket.com/albums/b89/willysworker/Red%20Dog/bellypanbacktofront2.jpg back to front
I still want the exhaust inside the frame rails and to exit out the back.
http://i17.photobucket.com/albums/b89/willysworker/Red%20Dog/RDrockslider2.jpg

Outside the frame rail exhausts get crushed and the noise right next to you gets tiring on a long run. I also run 32" tires and need everything protected. My 3a sounds like a bull doser sliding over the rocks.
Anyone with a CJ V6, SM420 and inside exhaust.

run duals all the way to behind the t-case, then cross it over, i think it will fit if your using sane sized exh. pipe. I had to run my exhaust that way on my blazer's bigblock cuz i wanted to be able to pull the drivetrain w/o pulling or cutting the exhaust

I wish the rails were as far apart as a Blazer. Flatfenders are really limited. Unless i dropped the T.C. there is not enough room between frame rail and T.C. . I'd love to dual it all the way out. But thanks for your reply.

looks like should be able to run some duals out each side if you put a flex coupler at the manifolds and semi hard mount the pipes to the framerails on each side. you can fit the pipes in hard places that way

Theres enough room for true duals inside the frame for sure, i had my flatty done that way originally with the 4.3 and 420. I will be doing a x-over pipe and single exhaust this time too, but i am running it as i described in the earlier post. I know that the manifolds may be causing you more problems on designing a crossover pipe on the buick motor than what i'm going through on my 4.3. I am using steel manifolds that are kinda like a header that i have cut and modified to fit inside the frame, around the steering linkage, and around the slave cylinder on the drivers side. Can you run a manifold backwards on one side of your buick, run its pipe around the front of the oil pan and into the exit pipe of the opposing manifold? Just a thought. Good luck!

ww sounds excellent, got any photo's. it's the thousand word thing for me.

I dont have my exhaust done yet, just my manifolds. Before i tore my jeep down for the rebuild i had dual 2 1/4 pipes inside the framerails dumping at the rear bumper. No pics of how it used to be. I was originally running a TH350 w/Dana 20, then swapped for a 420/dana 300. Both setups had plent of room for the pipe to pass be the t-case, although I do recall my passenger side had to be really close to the floorboard. Like i said before, you may be experiencing problems that I did not since you are using the buick motor. You could also try building your own Y-pipe/ manifold combo out of 1 3/4" tubing and build it up to 2 1/2" or so at the collector.
I am guessing that you have the drivetrain moved over to the passenger side a little instead of centered since you do not have room between the t-case and frame rail. My drivetrain is centered in my frame since I do not have the stock Ross steering box, or offset front and rear axles. My setup has a power steering box at the front of the frame and full width chevy one ton axles.

I guess I should look at this thread when I get home so that i am able to view your pictures, for some reason they will not show up on my work computer.

can you oval the pipe to get by the t-case--put a section in a vise and squish it where needed and then cut it off past the points of squishedness so that you can hook it back up to the down pipe and crossover---I did this on my twin turbo set up on my dodge to get a 5" pipe past the transmission---it's hard to see what room you have there, so I'm just tossing it out there as an option---chris

I was able to do a true dual exhaust in my 42MB with a buick v-6 and sm420/d18. Its tight, and I just dumped down by the rear axle, but there is room to go back farther.

I did have to make a special manifold on the drivers side that was a center dump to clear the steering shaft ( Saginaw conversion ) and the firewall.

I can take some pics if you want. Both pipes are inside the frame and above the bottom edge of the rails from the front spring mount back.