Non-traditional Chassis for a Traditional Custom: '49 Chevy Fastback Update

I guess we'll call this update #1...

I'm building a '49 Chevy Fastback for an esteemed gentleman in the Texas panhandle, and I'm making pretty good headway on the chassis. So I figured I'd share some pictures and a little commentary.

The car is actually going to be a strictly traditional custom on the outside. Something Sam Barris would have been proud of...chopped, skirts, different grille, bumpers and sidetrim....(hopefully) all the right stuff. However, even though the car is going to look like it could have been built in '54 on the outside, there's no reason it can't be fairly modern on the bottom.

Here's the car as it was brought to me....a great start for sure, but it sat like a 4x4. The solution? Bag it! Fortunately the car already had a Mustang II up front, and that would save me a little work.



So the first step was to brace the body and pull it off the frame. You can see the bracing just peeking out of the door opening in the body.



after taking some measurements, I decided I had a slight dillema...the front crossmember was going to have to sit on the ground when aired-out, and the tires would have to lay in at an extreme angle at the top if I were to leave things as is. So, after a little headscratching, I decided to Z the frame.

When Z-ing the front of a frame with independent suspension, it's important to bring the front crossmember 'straight up' to maintain the built in anti-dive. So I set up the front of the frame where the crossmember would be level, and marked a perpendicular line through the rails at what I deemed to be the best spot.

I also threw a quick brace between the rails to keep them from springing when cut apart.



The Z ended up being 2.5 inches.

I made gussets to fit the shape I wanted and welded them both front and back....so that when the top piece was in and the outside ground flush, the inside would still have an untouched weld. I don't have any pictures of that unfortunately, but here's the nearly finished product:



I tried to retain the "factory look" by making and fitting a piece to the bottom of the Z to mimic the Chevy's "hat-shaped' rail.

After all that was done, I decided to 'fishplate' the inside only.



It should be plenty strong...and one of the biggest advantages of the Z is that the difference between ride height and 'aired-out' has been reduced enough so that the tires hardly lay in at the top at all, avoiding the extreme negative camber look. Biggest disadvantage is that the trans tunnel has to be raised...but I was going to have to cut the floor anyway, so no big deal.

With the front end a little closer to the earth now, and set at ride-height with solid struts in place of the springs, I could switch my attention to the back.

First step was to lose the rear leaf springs.



I took some measurements to see what it was going to take to get the rear bumper on the ground when aired-out, and made some templates for doing a step notch out back. I ended up settling on an 8" notch, and the curvy design you can see here:



In order to keep the rear looking as much like the front as possible, and to retain as much strength as possible...I inset the plate on the outside only to keep the rail smooth on the outside. The inside plate was put on the outside of the rail.


For the rear suspension, I decided to go with a 3-link with a short wishbone on top. A lot of mini-truck guys use this set-up with airbags...apparently loosely based on Trophy-truck rear suspension. With the 3-link, I can do away with the panhard bar, and I can also retain more room for the rear seat, which will be a '63 Thunderbird item. The driveshaft loop becomes necessary, but it will fit nicely into the center of the T-bird seat.

Now that I made the decision, I needed a wishbone...so I ordered some tubing and rod end parts from suicidedoors.com. Before I made the wishbone I determined what the length of the lower links would be, and figured out how long the wishbone would have to be so that the front mounting point would be on an intersecting line drawn between the rear of the lower link on one side, and the front on the other.

The wishbone is made from .25" wall 1.5" OD DOM tube....heavy duty shit.



That threaded rod end is 3" wide with an 1 1/8" diameter bolt.



Now that wishbone was made, I had to figure out how to mount it. I made a driveshaft loop that would accommodate both the aired-up and aired-out ranges of suspension travel. I then figured out where it needed to be placed fore and aft to set the wheelbase.

Oh, and the rear step notch is a lot further along...



So here's the loop mounted and the start of the stepped X-member design I decided to use. I also have the tabs tacked on the rearend housing for the wishbone



Front tabs made for the lower links, airbag placement decided upon, and upper bag mount tubes tacked in place. All tubing used in the X-member is 1.5" OD 3/16" wall DOM tube.



I then had to set the engine in the chassis to set the pinion angle before making the rear mounts for the lower links. The carb base on the intake should be level or about 1 degree down in the back at ride height...Set that and then set pinion angle.



And here's the tabs welded and gusseted on the rearend housing for the wishbone:



So after the rearend housing was finish welded I stuck it back in the chassis, and could put the bag mounts in place. After that was done, everything was finish welded and it looks like this:



The horizontal tube tacked in behind the rearend is for the upper shock mounts, which aren't in these pictures. The lower link mounts on the rearend have bungs I welded into them for the lower shock mount.



Upper bag-mount and completed (except for metal-finishing) step notch visible here:



Here's the chassis a smidge below ride height in the rear...it will have about 5.5-6" of ground clearance at the frame rails, and about 2-3" more at the flip of a switch. Plenty for a tail-dragger.



And here it is aired out. The framerails sit on the ground just in front of the rear wheel. The front is still at ride height in this pic....it goes down until the trans crossmember is sitting on the ground.



I'll leave off with a quick shot of the changes necessary to the lower control arms in front, and the cups I had to make for the top of the bag. The cups mount so that the bag is straight up and down at ride height.



Thanks for looking...

-Brian

 

You do good work.

 

Hot damn... speechless...

Amazing, amazing work -- as always.

 

Thanks for the post. It looks awesome. Keep 'em coming.

 

Oh, and since there have been some questions about 3-link wishbone suspensions on here lately, I'd like to say that I have articulated the suspension without the bags in place, and everything moved fine. I'm sure there is some bind in the front rod end on the wishbone, but what little there is doesn't seem to hurt the suspension travel. You could change the rod end to a heim, but a heim would not stop side to side movement like the urethane rod end, and you would have to add a panhard bar.

The wishbone is the source of triangulation in this style of 3-link, and it seems to work great in stopping any side to side lateral movement.

 

That is a great looking frame. Very nice attention to detail

 

oustanding work that sucker is gonna be looooowwww. gonna have a sick f'in stance whens hes all said and done.

keep it up brutha...man im gonna have'ta visit tha shop soon.

 

Damn sweet work, man that's a hell of a frame. We use a similar V-Rod link on our big suspensions at work. Only difference is the single is on top of the pumpkin and the V is attached to the frame xmemeber. On a "normal" car you'd bind for sure, on a custom, you should be OK, as you said.

 

Amazing work! A lot of people ask how to get these Chevys down low...this thread shows one of the best ways.

Will you need to relocate the radiator mount to compensate for the Z?

Bryan

 

Boy howdy, I don't believe I've ever seen that layout before. Real nice thinking.

Worth looking at just to see your welds!

Looking forward to seeing more of this build.

 

holy crud. come to jersey and teach me everything.

666th post-mark of the Beast, HAHA.

 

great frame work did you make those notches?

 

good stuff. never seen a Z done in the front like that. it will be a shame to put the body back on and cover all that up....

 

bass


great work , but that bull shit about "esteemed gentleman" is not even close to reality

 

WOW! The best Designing,fabricating and welding skills I have seen in a long time. This should be one BAD BOY when done.
It only cost a "little more" to go first class.
Lynn

 

Great googlie-mooglie... wow.

I've never heard of or seen a "wishbone" set-up before this but it sure looks like a slick way to locate a rear with out a panhard bar getting in the way of everything else.

Very slick - thanks for showing us that.

 

Looks nice, i love the way its setup. any huge change in pinion with such a short wishbone and longer lower bars? you should toss up a picture with it fully lifted just for shits and giggles. i still want a 49-54 chevy so bad and am constantly running ideas through my head on a good way to put bags on one, your idea is the best ive seen and looks very well though out and executed! great job. edit- not that its a huge deal, but for anyone looking to do a wishbone setup, you can save yourself the welding and suicidedoors.com will build it to your specs. he's big on s10forum and im on there a lot so he keeps everyone up to date on stuff in their section on that forum, just a little tidbit of info for you guys.

 

Looks good. Glad you kept the top-hat shape thing going.

On the front, do you plan to "un-Z" the frame in front of the front crossmember to get the core support back down to where it should be in relation to the body? Or are you going with a crossflow radiator and a whole different header panel structure?

EDIT-- oops... someone already asked. I swear I read the thread, but didn't see it asked already.

 

love it ! post some more please.....

 

Very nice... I like very much...

 

AS always, you excell.

Quick question if I may, what ballpark lengths did the upper and lower links end up being, centre to centre?

Again, job well done, look forward to seeing more.

Cheers,

Drewfus

 

The frame looks great.

I really can't wait for the body modifications.....

 

that looks bad ass, nice welds too. cant wait to see the rest

 

There is a slight change in pinion angle when it is all the way aired out, but it will never be driven that low, so it's no big deal. During the normal range of motion that will be encountered by driving, it seems to stay at the pinion angle built into it at ride height. The pinion angle is also adjustable with this set-up, so I should be able to dial out any kind of harmonics I might experience.

As far as the wishbone being short, crawl under a late '70s GM product ( Say a '78 Monte Carlo for example) and check out the distance from the upper links' mounting point to the center of the differential. It's about 12" or so....the only appreciable difference is that it's a triangulated 4-link as opposed to the 3-link I used.

 

13" top, 24" lower.....thanks Drewfus.

 

You are a welding god.
Nice work. A level to aspire to fer sure.

 

No, thank you

Cheers, and look forward to seeing more,

Drewfus

 

Is there really enough length to the top 3rd bar on the rear.... seems like it has a very short stroke? I've never done one of these before, just asking. Your work is awesome.

 

Yeah I understand the difference and all and I've seen the 2 link setups on stock older GM vehicles but sometimes if the uppers or lowers and a lot shorter than the others it can cause some pinion issues with the top or bottom going at a stronger angle than the other, ya know what I mean? Don't get me wrong, I can plainly see that you have it figured out and know very well what your doing, I was just pointing out an issue that rises in some cases with a link setup like that one. I'm happy to see it worked out so great for you though, and again, it's absolutely killer work man