I Like It. Thanks for the info. I think I will insert some conduit tubes with some holes at regular intervals inside the frame before it gets boxed. I like the idea of the bigger holes along the frame to. Even if mud gets in there it will be easy to presure wash out and easy to get at anything I need to on the inside. Warping the frame was a definate concern so I will be carefull when welding for sure.

 

Holehawgg,
I am basically running the same suspention set up as you only I put a mustang II in the front I also used an IRS but out of a lincoln which is the same. I boxed the rear of the frame to the factory cross member and in the front I boxed from the rad support to the front cab mounts. I'm not an engineer or going to say that mine os correct. I do know that before I boxed it I could stand on the running board mounts and basically twist the frame as far as I wanted. Now with the boxing plates in even without a trans crossmember if I stand on the running board mount it will lift the other side of the fram off the jack stands. I plan to run my fuel/brake lines and such inside the frame as much as I can. I may also look at adding one of those K member kits as well but I dont plan to box the entire frame.
You can look at mine under one of my IRS posts. Obviously I havent driven it though. Not sure if it wil help you but here is where I'm at.

https://www.ford-trucks.com/forums/1...50-merc-4.html
Drew

 

One thing I would NOT do is run wiring or hardlines in conduit. Conduit is a great way to do wiring in a house that doesn't move (unless you live in CA ), but a vehicle is moving and vibrating. The vibrations will chaff hard lines and/or wires against the insides of the conduit as well as set up stress points where the wires/lines exit the conduit. It will be impossible to inspect or troubleshoot inside conduit. Where ever you run your wires encase them in plastic flexible wire loom or wrap with 2 layers of electrical tape then secure them to a horizontal surface with wire ties or flexible plastic clamps at least every 12-16". Don't hang or suspend them like Xmas lights. Any place they pass thru metal use a thick rubber grommet and/or a short section of rubber tubing to cushion and spread any movement. If running wires inside the cab, lay the wires side by side in a path where they won't be walked on and cover with a couple layers of duct tape.
You can hang hard lines on the vertical frame web with neoprene rubber bushed clips attaching them tight to the frame every 12-18". DON'T crisscross the lines over each other or string parallel lines so they contact or lay against each other. Again use grommets, rubber tubing and/or coiled wire spring protectors where they lines pass thru metal or better to use openings significantly larger than the line and support the line on both sides so it cannot vibrate against or contact the metal. Don't ever run the lines loose inside the frame.

 

Never thought about the vibration wearing the wires or the need to inspect them if something goes wrong. K, conduit is out. Plastic wire loom clipped at regular intervals inside the frame like factory is how its going to be installed. With the larger holes cut in the box plates it will still be easy to run and inspect if needed. And I admit the holes in the box plates will look kind of cool too. Brake lines and fuel lines will be installed there to or at least as much as possible anyways.

 

Good plan. Let the auto manufacturers be your guide, they have had a lot of practice and don't do very much that isn't needed.

 

I understand and admire the fact that you are doing your research with due diligence. When I was building mine I talked to many different, experienced people but did not know if the internet was even available then - mid 1990's.
My truck has a 1976 Camaro front subframe and original rear leaves with 2 removed and the axle on top the springs. To me it is ALL ABOUT the ride and the stance. I went with an automotive engineers recomendation and boxed the frame front to rear with added X members and remaining stock crossmembers welded solid.
It turned out just the way I was hoping. It rides better than most late model pickups I've ridden in (including my smooth riding '71 C10) and many newer cars. We (wife & I) take long trips - 2 -5 thousand miles - in our truck going to Goodguys shows (mostly) and it's a true pleasure on the road.
I'm thinking that your truck will give you similar results with the plan you're arriving at. My one possible question would be the IRS as far as stiffness. I've ridden in those T-birds and they seemed a little stiff TOO MY TASTE. These old pickups are pretty light in the rear with no load. That is why I removed the 2 leaves from my spring pack. I also had to try a few sets of shocks that were too stiff before I latched on to some from Pete & Jakes made for hot rods. Non gas charged fluid only type.

Have fun with your build, it will be worth it.
Steve

 

I only wanted to add that if the stock crossmembers, along with added crossmembers, are welded in, that you leave enough room so that the transmission can still drop down and out.... brake MC, too if it's left underneath. In the unibody 4x4 world, the tranny crossmember is typically still bolted in. My 2 cents.

 

AX, I've always respected your input on this site, you are very knowledgeable about many subjects. But you are off-course on this one. You are mixing chassis stiffness with suspension stiffness. On a four-wheeled, suspended, asphalt driven vehicle you really cannot get the chassis too stiff. Assuming you have a good working suspension. Once you go full IFS, the stiffer the chassis the better, for ride comfort and handling.

You are also mixing isolation from high frequency bumps, with overall lower frequency suspension compliance. Sure, if you solid mount all your suspension parts you will rattle your fillings out on expansion joints etc, but you could still have a very nice ride on a smooth but undulating road. Since roads like that are very rare, using rubber or poly to isolate the chassis from high frequency inputs is recommended.<O</O
<O</O

Auto manufacturers keep increasing torsional and bending stiffness of their chassis' (from model to model) in an effort to improve NVH (noise, vibration, harshness). Ride comfort is then tuned with spring rates, shock valving and judicious use of rubber. Race car builders increase chassis stiffness even more, but to improve handling. They take out the rubber and stiffen springs and shocks, hence the harsh ride.<O</O
<O</O

Gustave<O</O

 

I'm only doing a partial box. I've have seen countless mid fifty trucks with the M2 front end and 4 link rear end with just a partial box. Several which are used with small towing loads (campers etc).

Do you plan on towing a horse trailer? Off roading? Racing? Live in Arkansas? I might think otherwise then. But, for me, this is just going to be used like a car. In which case a partial box is more than suitable for me. Watch some of the videos of M2 installations they are using considerably less boxing than I am.

There is such a thing as being too stiff. ie. 2004 F-150. Vibration city.

Edit: I just don't think the benefit is worth potential drawbacks. I need the room for brake components and wiring.
Didn't realize you were talking rear IFS as well.

 

Hey AXracer , I have been thinking a lot (or a little , you can decide in a minute lol ) about what you were saying about everything being harder to access and install once you box the frame. Why can't you ,say, box the frame completely , but set the boxing plates inside the framerails by like 1/2 to 3/4 of an inch ? Then you can still have your lines and wiring "inside" the frame. Seems to me you would have a stronger weld this way as well since its a 90 degree angle instead of a butt weld. Thoughts ?

 

That's the way I do my boxing plates, but I only inset about 1/16 - 1/8".
Deep insetting would lend less structure since you would produce a smaller box, but not a lot. I really don't like making a box that is inacessable inside unless I was building a frame from scratch from rectangular tubing. It's always going to get water inside, and you have to re-engineer all the attachments. You won't believe how many things are attached to the frame until you start putting in all those crush tubes, threaded inserts, etc. and all those drill chips that fall inside are going to rust instantly. A main part of boxing plates with IS is to provide additional mounting surface, so insetting the plates means you will need to add additional surface at the the outside of the frame at those locations adding complexity and weight. With my 1/8" inset I just add another 1/8" doubler (or shim) as needed. If you don't mind your lines exposed then you might as well just attach them to the outside of the boxing plates as you would on a tube frame.

 

I've got Jag ifs and a Tci leaf spring kit on my F1. The Jag ifs is rubber mounted with stock Jag parts. I boxed from the radiator crossmember all the way to the rear leaf spring mount. I had some frame damage where the drunk who owned it previously had cut holes in the frame for mounting various stuff. BIG HOLES. After repairing the damage with 1/8" cold rolled, I boxed completely with the same cold rolled to insure that if my repairs were insufficient, the boxing would make up for it. I'm happy with the way it turned out. The ride is reasonable for a 64 year old truck, but it's still a 64 year old truck. NVH will never be up to modern standards.
Before boxing I installed everything that would bolt to the frame and welded nuts inside. For a few items I drilled access holes with a hole saw, but I should have made the access holes bigger. Be forwarned. I didn't run any plumbing or electrical inside the frame. All of that is fastened to the plates with rubber coated clamps and 1/4-20 bolts. All properly insulated and seperated.
I mounted my plates differently from the other responders. My toungue in cheek name for my method is inverted trapazoidal boxing. I don't like to weld upside down so I mounted my plates like this. The bottom of the plate is inset about 1/4" from the edge, easy weld. The top of the plate is even with and next to the top edge of the frame. Yes, the box is not square. The plate angles out from the bottom to the top. This allows me to make the top weld a butt weld that's not upside down. Chamfer the edge of the plate for good penetration.
After I boxed the frame I tried to remount a removable transmission crossmember I made, and it didn't fit. The frame had spread slightly. I was distraught. In that months Street Rodder magazine in the tech section they told a reader to expect the frame to spread slightly after boxing and to allow for it. I didn't feel so bad then but I wish I had know it alittle earlier.
Boxing the frame will make the frame torsionally stiffer as proven by the "step on the running board bracket" test, but you will still need to have proper crossmembers. My frame had the stock tranny crossmember removed and the frame was a flexible flyer. I could have probably thrown the steering wheel away and just steered by twisting the dash board. I installed a 1" square tube crossmember for the tranny which is about a foot to the rear of the stock x member. When I repaired what was left of the stock crossmember, bolt on with 1" square tube, it made a big difference.
A friend has a stock 51 F1 that I've driven. My truck goes straighter down the road, alittle less cab movement, but that may be the modern suspension. You can notice the lack of flex when entering driveways and such. There's alot less creaking and growning. What ever you decide to do is the right answer.

 

On my 54 I'm having to extend the front frame rails. I'm using rectangle tubing. I am going to have to bolt these extensions to my frame.

I will also be running some lines/hoses thru them for my water to air intercooler radiator that I'm mounting on the back side of the bumper. And some wiring for lights, etc. So to make things easier to get to I'm going to cut out some large windows in the rectangle tubes. I'm going to make some plates to cover the holes. And just bolt them on with some button head bolts.

This will give me fully boxed frame sections but I will also be able to get to everything inside the rails.

 

I'm a little late getting in to this one...but you ALWAYS box the entire frame if you use IFS and IRS. Partial boxing is used only when you use one or the other. The frame must be as stiff as possible for the suspension to work properly...

 

With all the responses I've decided on full boxing from front to back with several 2 or 2 1/2" oval windows cut into the plates for access to the brake lines and electrical that will be installed inside. This will give it the strength it needs as well as a way to clean out any mud that gets in there and it will let any moisture dry out quickly.
The tranny crossmember was in a post by AX. Going with 1 1/4" tubing on the top and bottom with 1" braces on the diagonal in the middle and a removable bar with the tranny mount on it.
All the cross members including the originals are going to be welded to either the frame or the box plates. This should help keeping the frame solid.
And finally, if the ride is to stiff then new springs and softer shocks should take care of it. You know what? I do believe a plan has been made. Now I just need to get out to the shop and get going on it.