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Frame vs New frame

14K views 34 replies 12 participants last post by  MARTINSR 
#1 ·
I have had a lot of positive feedback so far from this site. So here is yet another question I would like to learn on. I am in the process of putting my thoughts on paper for building a hot rod. I purchased a 46 chevy pickup with plans to fully restore. That plan has changed into building a hot rod. I plan on being low, fenderless, with a ls1 power plant setup. Now other than I have been told its better to go new frame than use the original. Can someone explain to me why??

My thoughts on the dollars going into it. I have been getting quotes on rolling chassis being built for me. I have yet to get a price on boxing my 46 frame in and adding some cross members for strength but knowing the price on one being built. I am thinking its going to be much cheaper to use the original frame, even after having some one beef it up. But again why is it still better to go new?

I hope I posted this in the correct section..
 
#2 ·
With the LS1 you should at less box the frame.. I try to build all my frames myself... When you do it your self you save a lot of the cost and you know what your getting..

This is only a few I hand built..





 

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#3 ·
Theres well over a half century of fatigue in the old frame. Know how you can cut a small strip of metal by bending it many times? That.

On the other hand, boxed aftermarket frames I have worked with are all flimsy sheetmetal with welded corners that look like they would split wide open in a wreck because of the merciless grinding done. The metal thickness can be alarmingly thin. I have yet to see one new that actually measures out straight by collision repair industry standards. I have checked a handful right out of the crate in my time. But these frames require no modifications for modern components as the old one will or might.

Boxing and reinforcing the old frame could create new stress hotspots but is almost certainly cheaper. Not sure which I would want if I were in your position, but those are a couple thoughts I have had that might apply.

You might want to look at mandrel bent pre-fab rails and consider starting from scratch. Kind of a mix of your two options, if something is available that fits your ride.
 
#5 ·
The original frame is a "top hat" design which, unlike Ford is already "boxed" but still not up to the modern power plants and speeds. A stiffener plate can be added to the outside of the frame but you will still need to put some sort of "K" member in the center. Bottom line is to duplicate the frame in 2 x 4 rectangular tube 3/16" thick. Add a MII style front end and whatever you decide for a rear end/rear suspension. The LSx engine/4L60E trans is a very good choice with lots of power and cheaper than a crate engine/trans. Over in projects/build on this site you can see my '39 Chevy frame build with a 5.3/4L65E trans.
 
#6 ·
You don't think 2"x4"x.187" wall is a little overkill??!! And it will weigh a ton all by itself.

I consider 2"x3"x.125"wall overkill when I do one, unless this is a very high powered deal (700+HP)with no roll bar included.

Most car trailers don't even use tubing that thick(.187" wall).

New Interiors, what about your thoughts on tubing spec?
 
#7 ·
Frame

Before I built my frame I researched materials and design a lot. Lots of the aftermarket builders use 2 x 4 3/16 inch for clips as well as complete frames. The older fat fender cars are a bit narrower and taller. A stout frame with weight down low goes a long way for stability. If you are building a race car then weight will work in the other direction and a lighter frame is a must. Constant pounding on the road, speed bumps and areas such as uphill driveways that are taken at an angle demand a heftier frame.
 

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#8 ·
even after having some one beef it up
if your paying someone else for basic fab like boxing the frame, you'll probably be paying for all your fab work
then a custom frame is advisable and will save you money

most of us here are DIY and do our own fabrication
boxing a frame is a relatively cheap process unless you're paying someone else to do it
 
#9 ·
2x3 or 2x4 seems awfully light for a truck. Thinner wall tubing is OK if you do some good cross bracing. 3/16 wall will be 50% heavier than .125. I used 2x6 x.125 Maybe overkill but there is zero flex. It was welded with a wire feed using .035 wire and enough power to get complete fusion.
A frame from 1946 is going to be rust city. boxing and bracing is pretty much putting a band-aid on a dead horse.
This is my Studebaker's frame..
 

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#11 ·
If you are going to build a chassis and plan on it being a hotrod with a eventual 8 point. I can not stress the gains that can be had by designing a monocrique.

A design of a truck series monocrique can be home built and adjusted to fit your cab. You can taylor different suspension setups to this setup as you improve upon it. Every piece of a monocrique serves a dual purpose to both improve the safety while being lighter then a boxed frame.

You can build a lightweight boxed frame. But by the time you add a 6 or 8 point then reinforce the frame to keep it from twisting you will end up with a heavy monocrique with overbuilt frame rails.

It is not for everyone. You maybe able to find a rolling chassis used by a truck series racer and work the cab onto it. There are also kits with prebent tubes. You will need to do the notching and I can not recommend a tn-250 enough. But having the tubes bent helps if you do not have the experience or equipment. From a budget standpoint going with a truck chassis with tubular frame rails may be a option if you want it to be built by someone. Most unprofessional shops is racers would be able to produce a proper monocrique for a substantial less then one made by someone needing to pay for a business and workers.
 
#12 ·
I'm not one to fab myself. I've never had a welder in my hands. Getting into all of this, I do plan on taking a welding class do to being so interested in it. I have a few friends that are welders in the pipe fitters union, they have offered to teach me some. But for this first build no I don't plan on trusting myself. As for the original frame, I can take pictures of it another day since it's at my old mans house. But it is solid. There's very little surface rust. I bought the truck in Indiana. The last time it was on the road was in the early 60s. Then sat in a barn.

The guy I've been working on a quote with does I believe 5x2, 10 gauge steel. All said and done I'm looking 15-16k shipped to my house.

This what we've worked on so far:

Standard Complete Rolling Chassis
? Perimeter Frame
o Boxed steel frame rails with 3/8? thick top plate for cab and box mounting
o tubular X-member center section
o radiator core support mount
o removable motor and transmission mounts ? Chevy LS/4L60
o Frame shortened 15? between cab and rear axle
o C-notch added to rear kickup
o Rear crossmember installed as close to rear end as possible. Leave rails long.
? Kugel Komponents IFS independent front suspension, including:
o Tubular A-arms
o 2? dropped spindles
o 11? disc brakes with Wilwood calipers
o Coil-over shocks
o Anti-roll bar
o Power rack and pinion steering
o Chrome Show package - everything but rack and pinion
? Complete rear suspension, including
o Triangulated 4-bar with coil-over shocks. Polished stainless bars and chrome springs.
o New Dutchman Ford 9" housing with new axles and 3.5 ratio posi 3rd member
? Hub-to-hub width = _____________________
o Wilwood 12? disc brakes with integral emergency brake and polished calipers
? Power Brake Package, including
o dual master cylinder, power booster, brake pedal, mounting bracket
? Other
o Auto transmission cooler, heat sink style, mounted to frame rail
o Bolt pattern = 5 x 4.75?

Price: $14,625

It's pretty competitive imo but I just wanted to learn why it's much better to go this route than getting bolt on kits for my frame after strengthening it by boxing in and having cross members welded in.
 
#14 ·
If you're doing as much fancy stuff as you list, then you will definitely want a custom frame. I've been welding for 50 years so I have a perspective on your skills. One of my complaints on wire feed is that "any monkey can do it". That is, if the machine is set correctly, all you need to do is pull the trigger and stick it together. That's not welding. Fortunately, you have some pipe fitters to help you. Use their expertise. Welding skill is a major part of fabrication but proper joint design is equally as much. Mil std 248-d is a great reference. Hopefully your pipe fitters are familiar with it. Good luck with your endeavor.
 
#17 ·
That does not seem bad at all. Look at some of those parts then consider everything is going to be painted or dipped. You are looking at 8 to 10K in parts. That is a good amount of labor. Even in the cbc world that they live in where it is cake to get a bolt on kit. Most bolt in kits don't or need adjustment. What he is describing is modifying the existing chassis with a large amount of parts. This is not a rolling kit there will be of of custom fabrication involved.

I am building my own rolling chassis right now and it is a very simple setup using leaf springs, truck axles, and bags with a few traction aids. I have close to 3k in equipment and 5k in parts. I am doing all the fabrication myself as it is a oddball and there is no kits or anything similar to use for a builder to start with. I stuff between 20 and 40 hours a week into the chassis. I only did. 7 today and only doing 12 tomorrow. If I could afford some of the 16 to 18k quotes for a custom one off chassis I would.
Not one person liked the idea on 1,000 lbs of engine with a divorced transmission. You tell them you want to drive it on the street, roll it a few times, then walk away they look at you pause and many give a stupid quote because they don't want to deal with it.

I have modified many chassis over the years. Something simple can quickly turn into a headache if you are not ready for it. There is a great deal of diffrence in what is needed for the track and street. I build for the street so they are overbuilt and dead on accurate or I start over. Most of all they are safe.

Maybe I missed it. But was there a cage in that quote?
I have rolled a couple cars and trucks. Speed has a funny way of making steel plyable. A cage may take up room, make entry harder, make things harder to work on, is heavy, and look out of place.When you wake up in the ditch and look back at all the times the thing flipped before stopping you will be glad you spent the extra bit on the cage.
Skate boards with a body laid on top are fine for show cars. IE 20 or 30 cars with no cage sporting a drive train meant to do 11s.
If you plan on driving the thing please install a cage mounted to the frame. I can't even remember the amount of times I have been told if this went this way or this happened you would very well be paralyzed or dead.

The most important thing that a chassis can do is support a cage to keep you safe. If you do plan on doing higher speeds in the thing a proper harness and neck brace are not a bad idea. Seats with head support sides,will help greatly in keeping you from over extending your neck in a crash. Having a vertical upright from the floor to the mid/upper windshield pillar will lessen the amount the roof collapses. A scatter shield will save your legs and bracing on the other side of your legs prevents your legs being crushed in a side hit or frontal fender to frontal fender hit.

There are lots of little things that make a safe street hotrod besides just the skateboard with the body on it. When building the chassis take these mandatory items into account so they can be added.
 
#18 ·
35K?????......If you read the original post (quoted above), you can tell the guy wants to do this for a reasonable price.......It also seems to me that he does not have the welding and fabricating skills to do this himself. I thnk he has some decisions to make........Either fork out a ton of money having someone else do the work or learn to do it himself. Personally, I think he needs to tone down his expectations, work on the truck as it sits now without welding and fabbing stuff, and hopefully he can make something of it. Too many people get in way over their heads with big dreams and expectations....Usually they dont have the money to follow through.....Just the way I see this.

BTW, I havent built a rod in a while, but the most I have ever spent is about 5 grand.....I guess times have changed
 
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#20 ·
Now if you just cant learn to weld or fab steel then think about other areas. Learn the engine part of the project or wiring or interior or all of the above. The op simply wont be able to have all work go to a shop and still get a good truck at a low price.
Power plant is all me and friends. As you stated I can grab a ls1 motor and tranny for around 4k. Tear it down myself, clean it up add a mild cam away i go. Right now I'm figure on interior being myself as well. That is always something that can be redone easily down the road. It's the frame work where welding and customizing that I don't feel comfortable with. I'd rather build a cheap rat rod for my learnings.
 
#19 ·
That quote is for only what is listed. So no cage.

Hcompton- that is were my thoughts have been. This is my first build and already interested in continuing after this with another project so maybe I could use the old frame else where.

I have the cab which is in pretty good shape. I also have the bed sides which I think with some work 2 of them can get re used so tailgate and cab panel needed. I have the grill and hood which are in amazing shape as well.

This quote doesn't include powder coating of the frame. I will need to get this done myself. But I figure the truck will be put together, driven down the road to make sure all is good. Then tore down for paint anyways.

I bought this truck when my son was 2 weeks old 2 years ago. I figured on it being a 5-8 year project. I'm not wanting to just throw something together. I want this to be the truck I get to hand down to my son or now daughter as well some day.

If I do this setup I'm quoted for, yes the project will be sitting for a couple months or maybe into next year depending on life. But I am okay with that.
 
#21 ·
hcompton has some good advise. I've seen more than one chassis that was cobbed together and were rolling deathtraps. Perhaps buying a prefabricated frame would be your best choice and use your other skills where you feel the most comfortable.
Since it sounds like you haven't won the lottery and you have a family to raise, you need to economize where you can. While the ads in the hot rod magazines can sell you just about every nut & bolt necessary, they also come at a price. Junkyards are your friend. The engineering has already been done. All you need to do is adapt. I decided to use Subaru door latches as my 2000 impreza had 246K on it and they still worked perfectly. They were also a compact unit with electric locks and the outside handle looks clean. A little investigation goes a long way. I'll probably have $5K into this when I'm done which is, to me, a goodly sum but 99.9% of the labor I've done myself.
 
#22 ·
Some people here are in overkill mode, I would say...
New frame is NOT necessarily better than original frame modified, it depends on a few things.
First, when you say "hot rod", what do you mean, drag racing 700HP, or cool rod for a week end drive?...
It also depends what you like, especially in looks and comfort... I personnally do not like the way a modern afetrmarket frame looks, with aftermarket suspensions... That does not make me right or wrong, just that I would not get an aftermarket/custom-built frame.
Many rods/trucks drive regularily with a modified original frame, without any issue: for instance, Camaro/Nova front clip, up-graded rear end, and your rod will outlive you, for instance.
On the other hand, you mention fenderless, so I am thinking original live axle would be the way to go for looks, so suspension/brakes up-grade and you are good to go...
An LS engine is a very good choice, but it is not either a monster motor that will brake you ride at the first stop light!
Maybe it is time for you to learn to weld?...
And keep it simple!
 
#24 ·
not sure why he started a 2nd thread
10'' chop and channel on a 46 truck set up for autocross
http://www.hotrodders.com/forum/channeling-chopping-46-chevy-416658.html
Started a new thread since it was a different question. I apologize if I shouldn't have.

To that 10" chop and channel. I will only be doing a 4" chop. I learned the cab will overhang the frame rails by close to 5" so I will already have that low ride look.

This truck will be driven any chance it gets. Just wanted to get an understanding on if I could save say 5k by using the original frame or it would still be worth buying new.
 
#25 ·
Have you considered simply placing the body on a different rolling chassis all together. I am not a stranger to dealer auctions and have always went in as a guest. Corvette or escalade have been mentioned. But, why not set your sights higher and look at a Cadilliac with a 2.0 turbocharged eco boost. These cars are getting popular as a simple front end hit basically totals them out due to. A side impact of rear hit would be better suited for your needs.

You should be able to pick up a late 2000's ats(awd)running ride and drive it up the flatbed for around 6I you can buy a non hit driver for 8 to 10k. Strip the body and set your hood and cab onto the unibody platform. You may need to cut and brace the in ivory to get your look. But, it has all been done before. Here is the thing you will probably end up needing to cut and brace the middle anyway. Well you have your opportunity to build a cage up from that. Once the cage is built you cut the floor out of the truck and lower it onto the car platform. Now you have a cage that runs front member to read and is far less noticable while saving your butt in a roll.

Brace, cut, trim, fit, tack, repeate. What you will end up with is a corner carver for around 15k that not only performs great, it gets great mileage, and replacement parts and service can be done at a shop. You also get a wealth of programable upgrades to Taylor the engine to your needs.

Now the Cadillac ats was just a example of a modern platform that could be used. That is just a platform that came with a wide variety of engine choices. I picked the awd 2.0 because you plan on daily driving it and it comes in both auto and 6 speed while being light. A ls swap is fine but if you want it to handle safe with a host of modern traction aids, that do help on a course, then fabricating the old great looks of the body onto a newer platform may be for you.

Now, this is not for everyone. But it has been done before. If your more into driving the thing then racing it then the newer platform thing may be for you. If you are into racing it with rules that say it must be x original and the frame needs to look original with only x modifications. I think your past that class though and the newer platform thing may be for you.

I am cheap at heart. This is the low cost way to get what you want. As stated when done with a cage and paint the frame mod and ls swap you are talking about will be around 40k.

What I am describing by placing the old body on a newer platform can easily be done for half of that 40k. Yes you can mess this up. Lots of precautions need to be done to make sure everything fits, looks right, and stays straight. But, it has been done before.
 
#26 ·
You are connecting the front and rear sections together using a cage/chassis. You still have frame "rails". But they are made of 1.75 dom incorporated into the cage to stiffen it further. You end up with a complete cage between the front and rear suspension pieces not a cage welded to the frame rails or bolted to a body with connecting rails attached under the body. The unibody itself is mostly thrown out. It is there to keep the dash, steering, and suspension items in place while your welding the cage/ tube space frame uni body together.

Once the cage is in place the floor can be reused and any type of cab laid on it if you do not want to fab a entire floor. But it is acting as only a floor and not a structural member at that point.

The biggest eye sore is going to be the rear suspension buckets that could easily be hid.
Like I said not for everyone. But comes in way under the alternative for someone looking for a driver more then a show car.

Yes it is heavier then just a body on rails. But it is also far safer with you having a full cage completely around you then just a hoop of sorts.
 
#29 ·
A car body bolted to the frame will stiffen it but this a separate cab & box and will flex big time. Were it a ranchero or a '63 F-100 then yeah. 2x3 ? wow. Not too good for longitudinal stiffness. Torsional either.
Here's some weight figures in lb/ft. 2x3x.120 = 3.884, 2x3x.187=5.59, 2x4x.120= 4.7, 2x4x.187=6.86, 2x6x.120= 6.332, 2x6x.187= 9.42
Ya pays your money and ya takes your choice.
 
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