Thinking of building a 25.1E chassis

[mike572]

I'm looking for some opinions and experiences of chassis builders. I want to build a 25.1E legal double frame rail chome moly chassis. I wanted to buy a unwelded kit from Tim Mcamis, Jerry Bickel, Vanishing Point or someone else. I have never built a complete chassis like this but I belive I have enough fabrication skills to do it myself (given of couse of chassis is in kit form with instructions). I am a skilled TIG welder also and welding the CM tubing is no problem. I wanted to run Art Morrison's super strut package up front also. What I am shooting for is a B/Gas street car project with plenty of strength to go faster in the future, although the car would only be driven on weekends and to car shows. I would be building this in a stock 70' Challenger body (not a pro mod chopped car etc.) and I would be building this in my garage ( I'm just a normal low budget guy haha)

So I have a couple questions maybe some of you pros would be kind enough to help me out with. Who makes the best/easiest unwelded kits? Does a Chrome Moly chassis have to be stress relived? How hard is is to run struts on a seldomly driven street car? Would you talk me into building it or out if it? Any tips?

Thanks ahead of time,
Michael

[bjuice]

read thru the site below..some good do it yourself stories in there.

i have also spoken with Richard Earle several times..very nice guy.
Suncoast would be my choice if i wanted to go your route

if you will click on the WALL OF FAME. you will see my 63 Vette. a VP fuel sign is noticable on the garage door in the background.

http://www.suncoastracecars.com/

[zipper06]

If you are a NHRA member and get national dragster, there is a newly certified (2008) 41 willy's 25.1 with MW rear and strut frontend rolling for $15,000.00, setup for B/BLK and Lenco, that's an unbeatable price if someone wanted to go promod. Area code 775, i think that's Nevada.

Zip.

[mike572]

Thanks for that Suncoast link, i'll definetly keep them in mind, Nice vette too.

Sounds like a real good deal on that 41 Willys, but I want to try to use the Challenger body I have, and i've been collecting parts for it for a while now. Thanks for looking out though.

[TopspeedLowet]

I'm looking for some opinions and experiences of chassis builders. I want to build a 25.1E legal double frame rail chome moly chassis.

So I have a couple questions maybe some of you pros would be kind enough to help me out with. Who makes the best/easiest unwelded kits? Does a Chrome Moly chassis have to be stress relived? How hard is is to run struts on a seldomly driven street car? Would you talk me into building it or out if it? Any tips?

Thanks ahead of time,
Michael

Well to help you with a few, Chrome moly can not be stress relieved by rule any longer due to the likely damage to the tubing that was being done previously. NHRA no longer recommends stress relieving of moly and is not required for chassis applications.
Struts are great on the street and every where but the street is hard on racing valved shocks and they over heat and get air in them quickly on street duty. A 25 1E chassis has welded floor boards on both sides now and It might just be me, but I do not believe that you will be effortlessly successful titling this chassis car legally for the street but that is besides the point.
Kits probably are helpful if you do not have a bender and have no plan to work with but I build cars for myself complete for less than $3000 for all tubing and interior tin work welded and complete race ready PLUS labor which is me thank god. The labor is the whole cost to building a car. If you are hell bent on a 25.1e chassis remember that NHRA changes and updates the chassis requirements often which if not used as a 25 1E during it's first 3 years may be a waste of money and tubing for you. It would take a lot of wind at your back to go faster than 7.49 ET.
25.4 chassis is much less pipe and is legal to 7.50 ET. The floor has to be welded on the drivers side only and is more condusive to updating this way. As a welder you have to treat this moly like you are welding on 18 ga steel. Only go 1/4 at a time and don't try to do the whole weld at one heat cycle. Avoid over heating and pulling the pipe, make all your joints tight and one pass only with .060 crown 8 filler wire or 80 stensel strength.
Bruce

[mike572]

Bruce,

Well i'm glad the chassis doesn't have to be stress relieved thats a big worry off my back if I make the chassis. Alright I was planning to run Art Morrison super struts, I don't know if your familar with them or not but they seem to look ok for the street, your mainly talking about struts like Lamb having street issues right? Over here in California i've just been renewing my registration on the car and nobody has to check the modifications made so as far as they know it's just a run of the mill 70' Challenger. I do have a Greenlee hydraulic bender but the one part I was shying away from is designing it myself since I have never done a whole chassis before. Do you know how entensive the changes on a 25.1e have been in the past? I wouldn't mind moving a few bars around every 3 years but if they are major changes I might have to reconsider. I'm guessing the 25.2 changes vary heavily like the 25.1e every 3 years? The main reason I wanted the 25.1e chassis is beacause i'm planning on keeping the car for a good amount of time and with the engine/trans combo the car should run mid to low 8's when it is done, so I wanted to have plenty of room to go faster in the future if I need it. I'll definetly look into the 25.4 chassis you got me interested already. When you say the floors have to be welded on both sides you mean the 2 thin sheet metal floor panels have to be welded to the frame right? And this would make future updating harder because you have to destroy the floor panels to move the tubing underneath? Thanks for the welding tips also.

Sorry to bombard you with all of these questions but I really do appreciate you helping me out with this.

Thanks,
Michael

[zipper06]

The best idea is to go here and order the spec sheets, they're only $35.00 and that way you won't get any surprises.

Zip.

http://www.sfifoundation.com/

[mike572]

Zip,

Yeah, i'm definetily gonna get one of those books before any construction starts, thanks.

Thanks,
Michael

[ashtrak]

A car like yours you almost would have to build from scratch unless one of the top builders has blueprints made up. all of Bruces points he made are true exspecially about the welding in 1/4 sections and not to overheat it or it will become brittle and the welds will crack. The sfi book is the only way to go for the specs and right tubing you need like zipper said. I feel anonther important thing to a build is the planning of the whole car as to where and how everything will get mounted or you will be wasting time and money adding things then cutting them out to move it. remember to also drill small holes ( I use a 1/8 inch) where you joints meet to relieve pressure built up from the weld exspecially on small pieces out they will blow back.you have to have a place for the gases to go. Clean your joints and intersecting places ( I use a scotch brite ) inside and out and acetone to wipe clean. Good luck in your project.

[TopspeedLowet]

To give some clarification on what I said about the floor. The .035 steel flooring must be welded on both driver side and passenger side to the pipe (on the inside of car) and not riveted as I would prefer, so when NHRA decides to add a piece of pipe or up size one, you would have to destroy the flooring and anything in your way to do it. As for the chassis design Ash is correct that each chassis is like a snow flake to clear your car body and fit you. It has been my expeirence over 25 years of building my own cars from scratch (and quite a few others) that over 80% of the job in time is coming up with a design that works with the chassis and laying everything out accurately, within perfect would be OK, not within 1/16". Only 20% of your time is fitting and welding which is the gravy part. The struts that I mentioned that are not likely going to like the street were the Strange, Lamb type agresively valved for drag racing. The rear shocks will need to be street quality also to survive street driving of any regularity.
The SFI foundation has books that they sell for guys like you and I that just need the rules to build your own car. I think Zip highlighted that for you in his entry. These books do not tell you how to build the car, They are for tubing sizing and angle limits and locations which are very general. Every chassis will look different than another with the same classification level depending on the body they fit. Your finish chassis does not have to be the exact same as the books examples they provide. They are just examples and the writing part is the most important part to follow. You will likely need to check with a chassis builder now and then and possibly a NHRA tech inspector to ask for interpritation of the book for certain things possibly.
Don't be intimidated by the the job, It is very rewarding work and as a welder you can save the bank by doing it yourself. You are trying to build a car that would cost you $65,000 to order and pick up and there will be a lot of work and learning. Just get a good plan and make it happen for yourself. Remember that SFI doesn't make cars or design them, they make safety rules and strength requirements for the driver only. The car design is your baby. :D
Bruce

[promod45]

Another thing you might consider is that Tim Mckamis chassis are not adjustable in back so if you want to adjust ride height you cant,i am doing one right now and we will have to buy shocks to adjust ride height, so before you buy a kit ask alot of questions and make sure you can adjust it if you are going to street it, i would check into a chris Alston Chassis as they are very good stuff, very helpful, and there chassis can be adjusted for different rides,, good luck

[mike572]

ashtrack,

Yeah I'm having a lot of trouble finding a kit for the car, I figured it would be available since the Cuda also has the same exact layout. Thanks for the welding tips to I'll definetly do it 1/4 at a time.

Bruce,

Thanks for clairifying the floors, that does seem like a hard future upgrade. I'm thinking about building it from scratch now like you said or at least giving it my best shot before I pay a professional chassis builder big bucks. I can't find any kits for the car. Do you know if the Greenlee bender I have would work fine for the CM chassis tubing? It doesn't have to be mandrel bent of anything fancy right? On one website I saw had a chassis builder using PVC pipe to plan were all the steel bends would be. He didn't make a whole tube chassis but he did make a 10 point cage. First he made the whole cage out of PVC pipe, (he heated it up and bent it with a torch to make all the bends) then he transferred the PVC to the steel tubing and thats how he made the rollcage. Have you ever done anything like this? Or should you just jump right to the steel and the PVC is just a waste of time? Also what do you usually do about the body, do you have to brace it all up before cutting out the stock floors? I'm afraid once the floor comes out the body will twist and the doors won't close anymore. But then at the same time how do you get inside the car and plan all your bends and lay out tubing with crossbraces all over the place. So basically if I built it from scratch I would want to bend everything, tack weld it into place all with the body on the car, trailer the body and chassis down to a professional chassis builder (I already know one) and have him give me a final seal of approval then go home and (given I did everything right) seperate the body and chassis then fully weld the chassis, then put the body back on. Am I thinking the right way about this? I'll defiently follow that SFI book as close as possible to make sure it passes. I've always wanted to build a tube chassis car myself. Thanks for all your help on this.

promod45,

Alright, i'll definetly keep that in mind. I was curious though, what exactly do you mean about the back being adjustable? Do you mean the 4 link? Or is is something to do with the crossbrace for the shocks?

Thanks everyone for your help I really appreciate it,
Michael

[TopspeedLowet]

I use math and calculus to determine the bend locations like I used to when I was fitting and welding pipe in my chemical plant days. Each bend has a bend radius and a gain that you take in effect for each bend. PVC sounds like a hot rod magazine tip or something like that. I would avoid advice from someone that uses PCV to lay out a chassis and calls them self's a chassis builder. I might suggest that you try using a piece of wire or something like card board to lay out bend radiuses. Wire is re usable. The bender only bends one radius, not what ever you can bend wire or pvc to. Once you wrap your mind around the concept I am confident that you will figure it out.
Often the benders come with some starting instructions that you can start off with. As for the bender, the type will limit how many degrees you can bend any one bend. Some will do 180 deg and most don't. The bend quality must be wrinkle free and without necking. Mandral bending is not required but a good bender is. The key to a good bend is lube and clean, clean, clean.
Now the body. Cut her loose and mock up a brace that you can use to hold it safely in the corner for measurement purposes and trial fits to your cage.
This is the only way any car can be perfectly strait is by putting it that way. When I mount the body I try to be sure that every thing chimes ( Is perfect as possible) to every piece of the frame centerline.
Remove the doors and re mount them later when you are mounting the body for the final fit. You can make the car better than the factory ever could have. Stay with it and go one direction and you will get there every time guarantied.
Bruce

[mike572]

Bruce,

Yeah, that makes sense why not to use the PVC. By necking do you mean how some benders turn the tubing into an oval with a ridge?

This is the bender I have, have you ever used anything similar? If I use it properly with lube and have everything clean it should work right?
http://i53.photobucket.com/albums/g52/freshsb1/Picture4.png

I'm a little confused though about what you mean with the bracing, should I brace it so the braces are running through the cage and not hitting any tubing? I should be building the cage inside of the car right? Not off to the side? Also what did you mean by hold it safely in the corner? Am I right about tacking the whole chassis together in the car then taking it out to flip over and weld? Or do you usually fully weld it while it's in the car? If you seperate the tack welded chassis from the car to finish welding it and the braces are running through the cage you would have to take the braces out. And that would be bad? And your saying it's best to remove the doors right before putting the body on the chassis for the final time? I was wondering why it's better to take them off instead of leaving them on.

Thanks a lot,
Michael

[TopspeedLowet]

You will find that the thicker the wall tubing is the more easily the tubing is to bend with out wrinkling. You will have to do a trial and error attempt with some tubing samples. You may find that 1 5/8" .083 is hard to get a good 90 deg bend on but if you use the next thicker wall thickness it bends perfect. This is common and there is not a down side but the extra weight to using thicker wall tubing. SFI is minimum specs.
The body. The reason I would remove the doors is only to relieve the A pilar while you are removing every thing that it is hooked to that supports it. The extra weight of the door will just tax your back and the car form while sitting on saw horses in the corner. The braces I was refering to were to create a cradel that your body can sit on supporting it adequetly to prevent damage to the rockers if that applies. I have never built a Cuda before and do not have a visual in mind on your car chassis. The body needs the front fenders removed and the doors to lighten the body so you can pick up the body and do occasional clearence checks along the way. The body will be like an empty refridgerator box when the floor is cut out. You need to know what the original dimensions are between rockers and respect the original blueprint of width dimensions you establish and set it exactly over the center or the chassis in mock up.
Welding is required to the roof near the A and B pillar's to the cage so the paint is gona get damaged to an extent. The cage and the body will become one when you are done so you need to support the body every where you can easily to hold the body in its exact original form that you are going to re animate when you hang it on the chassis. Put the doors back in the jamb to fit the openings perfect when you are done picking it up over the chassis.
I don't want your head to explode, but there are quite a few steps required to build a car from scratch. As long as you understand everything about drive line angles, the geometry built in to in the front end mounting locations, and have a basic understanding or roll centers, torque vectors and enjoy physics. Everything is real simple to do it is just making the first choice which dictates the next choice and so on.
I had this boss that used to say (if it were easy every body would be doing it bud) and somehow that was supposed to make me feel better.
It is easy to build a car but it does require a lot of choices that dictate other choices. But then again it can be very rewarding to build your own car if you are willing to do it until you are done.

Bruce

[Drtmod5]

Check out this site. They have lots of choices listed. http://www.vpracecars.com/

[mike572]

Bruce,

Alright, I'll definietly do some test bends before anything serious.Removing the doors makes sense now, i'll definetly do that. And as for the cradle your were talking about, Should I make it out of thick plywood with 2x4's braced all along the bottom of the car this way there will be no brace bars in the way of the cage? Are you not supposed to have any brace bars running through the inside of the car? If I can fit a couple above the cage so I can easily take the body off should I only do that? Or just the plywood and 2x4's cradle along the bottom? Or do I have the wrong idea with a plywood base all together? The Front end is going to be a fiberglass clip so there will be no front fenders so that's one less thing to worry about. And should I have the doors off while i'm coming in and out of the car taking measurements and bends? Or leave them on and just open and close them waiting until the final body mounting to take them off? I'll also be sure to take all the measurments I can before cutting the floor out.

I've had tube chassis cars before so i'm pretty familiar as far as the angles, geometry and such. And I have one of those huge mopar race car engineering books so I think I should be alright on that, given I study the book before designing the chassis. Yeah I guess thats why racecar fabricators are really on every corner haha, but I'm very willing to make the chassis and finish it.

Thanks for your help,
Michael

Hambone,

Thanks for the link.

[TopspeedLowet]

Bruce,

And as for the cradle your were talking about, Should I make it out of thick plywood with 2x4's braced all along the bottom of the car this way there will be no brace bars in the way of the cage? Are you not supposed to have any brace bars running through the inside of the car? If I can fit a couple above the cage so I can easily take the body off should I only do that? Or just the plywood and 2x4's cradle along the bottom? Or do I have the wrong idea with a plywood base all together? The Front end is going to be a fiberglass clip so there will be no front fenders so that's one less thing to worry about. And should I have the doors off while i'm coming in and out of the car taking measurements and bends? Or leave them on and just open and close them waiting until the final body mounting to take them off? I'll also be sure to take all the measurments I can before cutting the floor out.


The body cradle I meant was like plywood frame as you figured, that the car body can sit on while waiting for a fit and holding the body at dimension if that is necessary. The doors are one more item in your way during cage fab but you just need to respect there space so they fit later. Your car body may be sturdier than you think when you gut it out and may not require any fixture to hold the rockers on dimension, just a wood parking spot to be kind to the rockers.
I have built cars inside the body once I complete the floor structure on My jig then the rest free standing in the body, and I have on some, had the benefit of being able to remove the body like you do and weld out in the open. You can do what ever you can work around and weld completely. You may leave the body on wood shims off the floor over the frame with a few pieces of pipe holding it in place temperarly in perfect reference to the lower frame height and center line for all your cage pipe layout, then once the top is determined and your fit and tacked you may choose to remove the body to make a gravy job out of welding the cage in. There is not a correct way to do it. It is a matter of what you can work around. I would recommend doing as much with the body mocked up over the frame as possible. This will allow you to get much closer to the body to make the most of your driver space. The body will need to be welded in several locations to the frame but the roof area will only need 4 spots, Over the A and B pillars in the roof corners or where there are area's of reinforcement are good locations. But again, there are other locations that you can use that are correct for your car, but two up front would be wise and at least 2 in the rear to hold the windows in is recommended. Don't over think the cradle, It was just a suggestion to hold your baby when her skeleton is being fabricated and kept on dimension to be handy if you happen to need to check a measurement while you are welding and laying out the cage. Your bender type will make it difficult to back up bends. Some times you need to transition bends or appose bends. You will be able to get the job done if you are efficient with your bender.
PS. A tremell is your best friend for squaring the body and rockers on the stands or fixture. It is a body guy tool used for checking frame squareness or a toe in checker if you are a drag car guy.
Bruce

[mike572]

Bruce,

Alright, the cradle sounds simple enough. I just wanted to make 100% sure the car wouldn't turn in to a pretzel haha. Great Tip with the body and frame on shims to determine the frame centerline to, i'll definetly do that. For the flat part of the base do you usually just lay it out on plywood with small wood blocks nailed in place to align everything? Welding the roof to the frame should be fine beacause the car is not yet painted, just primered. I've seen cars with the roof braces up front, that does look like a good idea, I'm sure I would want those.Those braces over the rear window sound like a good idea also. Makes sense to tack everything in while in the body is on then take it out to finish welding. I'll have to look into Tremells, i've never heard of them. Sounds like a neat tool to have for this job. Do you know roughly how many feet of tubing is used for a chassis like this?

Thanks,
Michael

[TopspeedLowet]

The way I do the base frame is on a large 1" thick steel table and clamp everything down on quardinate and weld 100% prior to releasing. The table has windows in it for this purpose but you do not need to have a table. You must have a strong back of some sourt or a jig makes the job easeyer but not necessary. Just make everything perfectly level and square. No biggie.
As for holding the body in place over the frame. I weld splines or pipe pcs to hold it on dimension to the frame so I don't bump it during working while it is on the shims over the frame, and the shims you use to level can be any variation you choose and feel will hold everything in place most fab guys use steel shims but wood is just fine too.
As for the pipe quantity's that will depend on how you make the double frame rail and what size pipe you choose to use weather it is 1 1/2" or 1 5/8" and so on. Here is a preliminary pipe schedual for getting started.
A stick is a random length 20' piece of pipe
6 sticks + of 1.625
4 sticks + of 1.5
3 sticks of 1.375
2 sticks of 1.25
2 sticks of 1
2 sticks of .75
2 sticks of .5
The smaller tubing like the 1.25" and smaller I would use minimum wall thickness NHRA allows, and the larger size pipe you will need to determine what your bender can use effectively with out necking the pipe or putting a ridge in it.
I would get a few square feet or 1/8" 4130N plate for brackets and one sf. of 3/16" 4130N plate. The better you are at making brackets the less plate you will need. If you are making your 4 link brackets too you will need 1/4" 4130N plate but make a templet first so you know how large a piece you need to cut them out of.
This will get you started and possibly finished. The more pipe you have in stock the better you can do bending the pipe. You will be braver knowing that you have more in stock for errors. Error bends can be helpful sitting in the corner for other parts like the funny car cage etc.
Good luck with your project
Bruce

[mike572]

Alright, Sounds like a plan. Thanks so much for all your help Bruce, I really appreciate it. I can't think of any more questions right now but if I do i'll send you a message. I'll send you some pictures when it's done to.

Thanks,
Michael