My th400 deep trans pan is basically the width of the frame rails and my 3" true dual exhaust hangs far too low and is catching on everything because of this. Was debating using some spare roll bar tubing I have and welding a support from the front section of the subframe to the subframe connectors I have that run along the outer rail of the chassis. They're the jegs brand box tubing ones, so welding to them would be easy. Then cutting off the part of the subframes where it necks down too narrow, to get me enough clearance to run the pipes along the outside of the trans pan. Would I have any structural issues doing this and just "capping" off the material I removed with some 1/8th plate or something similar. Just looking for ideas here.



EDIT: started my cutting on post #52

 

Go for it.

Portions of my front frame rails have already been trimmed for header clearance. Using a longer SFC to tie the rear to farther up on the front is fine.

If I could, I'd run new frame rails right up to the firewall area and remove all the factory front subframe under the body. I'd modify whatever I had to and move my engine back another 6" if it wasn't for the fact that the headers won't fit between that narrowed area.

 

that sounds about like what i'd like to do

 

As long as you are going to tie it back to the sub frames, i dont see why it wouldnt work, might even be stronger.

 

Post some pics when you finish. This may be a good option for us LT header guys.

 

Here is what I did.



I am in the process of repainting the bottom side after the 25.5. My 1 5/8 tubing is connected to the lca's in the rear. I also cut out my original sfc's because they are not needed anymore since the rollcage is tied into the 1 5/8 connectors.

 

So you just cut the subframe off and squared it off in the front it looks like. Any chance your car is still on a lift and I can get a closer up picture towards the front there?

 

Both my car's(the 10.5 car and my street GTA vert) are done very similiar to that. - No problems with either and for sure a lot more room.

 

shagwell you have any pics as well?

 

Yes, it's still on my lift. I'll be under there tonight and text you.

 

Take as many as you can and please post them up.

 

I did this too.

 

here is mine

 

so did you add any cross bracing at all to the chassis or just cut and plate the areas?

 

I'm curious as to how the 25.5 is allowed without the x-bracing under the driver seat? Without a 25.5 spec book, I don't know the full requirements.

Since I need to redo my mid plate to raise the tranny and back of engine higher, I'll also need to fabricate a new tranny crossmember. Maybe while everything is apart, I'll consider cutting out my old SFC and doing something similar. I don't know if I'll need to cut out the tranny tunnel yet. I use a CSR shield so clearance isn't that bad but it's going to be tight.

I'd also like to see more of a closeup picture of exactly what you did at the front of those tubes. You've peaked my interest.

 

oh man, i'm so going to do this one day...

 

Hmmm. Very good idea.

 

The car is 25.5

 

Looks great stiletto. I'm just hoping running a single bar from the subframe left to the connectors will be enough since I'm obviously not 25.x'ing the car.

 

25.5 does not require the full X-braces if you have complete stock floorboards. The X is mandatory for tin floor cars like mine, but with tin floors most will add the couple tubes for 25.4 and allow the extra .5 ET.

Mine has the front rails cut off square with the bottom of the kickboards; none of the factory rails are left under the floors. I did the same on my GTA years ago, but it has 2x2 box welded straight back through the floor as more of an "in floor frame" than just subframe connectors. - There's an old thread on here somewhere that shows my fully tucked true duals; it has pics of the frame work. I was like 16-17 and using a stick welder though, so not a pretty as it should be.

 

My subframe is cut off at the firewall, capped off, and 2X2 box tube ran through the floor.

This is how the chassis shop did my car. I have a ton of clearance for exhaust.

 

looks great red....exactly how I'm planning on cutting shortly. Just waiting for the motivation to do it on my back since I don't have access to a lift

 

Red looks good do you have any pictures of where it ties into the back?

 

hmmmm....ya'll are going to make me work on my car again

 

I was thinking the exact same thing. Car is still on 4 jack stands and I'm just about ready to pull the tranny. I think modifications will be done before the tranny goes back in

 

good call. when the engine/trans come back out (for whatever...no telling what right now), i think i'm going to do this

 

I did 2x3 boxes before my round tube deal and it wasn't that bad on my back. It sure opens up the exhaust possibilities.

 

Too bad this isn't legal for x275

 

what isnt legal for X275?

 

front subframe cutting and boxing off isn't legal?

 

Thanks.

They are tied in under the rear crossmember in front of the 4-link brackets. These are the best pics I have of that.

 

The thread where I asked...

http://www.yellowbullet.com/forum/sh...d.php?t=283006

 

Well, I was under the car tonight pulling the tranny. Just the bellhousing bolts remain. While looking around, I can easily see how to redo the SFC but the front mounts will be a bit tricky. I've already hacked up parts of the factory front subframe sections that go under the car for header clearance. A bit of planning and some patchwork and I could have a good support to rejoin the SFC right to the front subframe just below the firewall.

I haven't really decided on round or square tubing yet. 1-5/8" round would be nicer than 2" square. Local steel supplier has lots of 1-5/8" x .125" DOM. That way I could easily incorporate diagonal bracing similar to stiletto's picture above.

 

Yikes!

I cut out the passenger side SFC that was installed many, many years ago. The driver's side will take a little more work as the seat mounts are welded to angle iron that's welded to the SFC.

I then cut out much of that sheet metal subframe under the floor to a spot up near the firewall. There sure isn't much strength in all that sheet metal for the SFC to attach to. Makes me wonder just how good attaching SFC really does in these cars. The sheetmetal subframes are really thin.

I cut them off just behind were the SFC has a section going off towards the outside. Very similar to where 1BADRZ28 has the front mounted. I need to modify and plate the front section for a good base to weld new tubing onto. Sure will give me a lot more room for the 4" collectors after it's done.

I do have one advantage. Because I use a front and rear motor plate, a tranny crossmember isn't really required. I fabricated a basic crossmember last year. It held very little if any of the tranny weight. It was more for a place to mount the driveshaft loop onto. I'm going to ditch the tranny mount and fabricate a simple driveshaft loop mount instead after the new frame connector tubes are in place. That will shave off a few more pounds. I think the 1-5/8" DOM tubing I'll be using will weigh less than the 2" square tubing the SFC were originally made from.

The rear mount point is going to be easy. The tubing will simply be welded to the back half crossmember. Doing a quick measurement, I need two pieces of 1-5/8" tubing 4-1/2' long then trim a couple of inches to fit. I haven't decided if I'll X-brace between the back section of the tubes until I see how well everything fits.

 

Any pics yet stephen? I'll also be welding the strut tower "caps" around the chassis this week, just waiting on another welding blanket to come in since my switch to coilovers as an added strength measure. Hoping next month will be slightly warmer since my attempt at putting rubber sheets down caught on fire to protect me from the frozen garage concrete.

 

No pics yet. Not much to show yet other than one front subframe extension cut off. I'll be picking up some metal on Saturday. My MIG gas bottle is getting very low. I don't think I'll have enough to finish the weekend unless I can get the bottle filled on Saturday while I wait (don't know if it's possible). I own the bottle and the place I bought it from is out of business so a simple bottle swap from another company may not be possible. It's only a small bottle about 2-1/2 feet high but it's all I need.

Even though my cage uses sill bars, I still want these tubes to join both subframes. The main hoop of the cage is welded to the rear crossmember but the a-pillars, door bars and sill bar still join to the car by the 6x6 plates welded to sheetmetal. These SFC tubes may not really be needed but in these unibody cars, they should still be used. If room is available, I'll eventually join the A-pillar tubes somehow to these frame connector tubes and some day I'll finally go through the firewall to join the A-pillar tubes to the strut towers. At least I've got some tubes from the front of the strut towers down to the front of the frame rails to add a little support.

I'm lucky that my garage is heated I have it set on a cool setting just enough to keep the chill off but crank up the furnace when I go to work in it. Having a heated detached garage was a requirement when I was house hunting.

 

Got a picture! The center part where the tube is going to attach to is actually a piece of 2x2x3/16" angle iron. The other part goes inward. I figured it would add more strength than just a flat piece of metal. I was able to weld it in before plating the side.

The bracing on the right side of the center plate is OEM. The front subframe was square/rectangular shaped and you can see on the left side how much of a diagonal I had trimmed off for header clearance. Some leftover 0.090" flat plate from the mid plate (you can see the engine supported by the midplate) provided a good piece to cover up the hole with. As with many of my projects, trial cut pieces of posterboard to get the right shape then cut it out of metal.

It sure was nice being able to remove the slip on collectors for access. The tranny was already out because I had to relocate the midplate higher to get a better driveline angle to the diff. Those are 2-1/4" primary tubes.

OVERHEAD WELDING SUCKS!!

 

Turn the gas up higher(another 5-10psi) on your regulator when you're welding overhead like that. It escapes from the burn area to quickly/easily when upside down and lets the weld contaminate, thus is a PITA to do.

 

I found that increasing the wire speed a little helps tremendously when welding upside down as well as higher gas pressure.

 

would this be safe to do on a street car, need max ground clearance with my automatic and longtubes.

 

Ground clearance won't change since the new tubes should never be lower than the current subframe parts. Looking at mine, the tubes will actually be higher than where my old SFC were. The headers and exhaust are my clearance issues. I think the lowest part of my exhaust is around 2-3" off the ground. I've scraped them backing out of my garage because there's a downward slope after coming off the garage floor. I've never had a clearance problem driving around the pits but on the street, big speed bumps could be an issue. The SFC would never be a problem.

I got a new gas bottle and picked up the steel I needed today. If the girlfriend will leave me alone for a while this weekend, I may get more done. Somehow I doubt it.

Moving this thread to the fabrication forum.

 

Are these cars prone to tearing out the LCA front mount? My car does 1.27 60s and they are not reinforced like that. Do I need to look into that?
Sorry for stepping in the middle of your thread, really learning alot.
Thanks

 

When I was still using the torque arm suspension, I never had a problem of hurting the LCA front mount however, the floor area in front of it was starting to wrinkle on the passenger side from all the hard launches. The LCA mounts are very strong. Probably some of the heaviest pieces of metal in the suspension system. My old SFC were basically attached to the same metal in that area.

My update. The passenger side tube is in. No pics yet. It went in real nice but having the 4-link crossmember really helped. I took out my seat and cut the mounts off the floor and SFC then chopped out the drivers side SFC last night. It was much heavier than I remembered. After I plate the front subframe for the new tube and weld it in, I'll need to figure out a new way to mount the seat to the framework. I can't just bolt it to the floor.

 

Man I wish you guys had lifts just for the use of taking better pictures. This tread has basically just relinquished my thought of buying SFC's. Even though most of you guys are building hardcore drag cars, almost all of these principles can be mirrored on a street car.

$250 in mild steel can go so much further with the right design.

 

Another picture of the front but with the header collector on and the tube welded on.

This is how I attached the rear. With much of the original floor on the passenger side removed, access was easy. The driver side needed the floor hammered up a bit to get the driver side tube in roughly the same position as the passenger side.

I'm working on getting the transmission and shield back in before tackling a driver seat mount and a driveshaft loop mount. Then I'll fabricate some new exhaust hangers since the old one were welded to the old SFC.

 

This is a great thread. Nice work. I was thinking about doing something simular on my car. I think I will get rid of the cat hump in the floor at the same time.
Kory

 

I had some sheetmetal movement years ago when I was just running 9's. It's piece of mind.

 

Thanks, I'll keep an eye on it.

 

I get why you did it but just hanging down like that you're not adding nearly as much strength as you could be. Most of the others have substantial portions of their tubing going through and attached to the floor which gives them much more strength. At the very least I would consider something like some sort of boxing or webbing to the floor to add some more rigidity.

As far as the LCA pickup points, most people don't see much movement there unless they're running a lot of power, tire and lower then stock LCA brackets, OTOH, most subframe connectors attach to that area and many box it.

 

These are some great pics! This is the plan!