Chassis stiffening for street car

Shocks, Springs, Brakes, Frame, Body Work, etc

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panic
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Re: Chassis stiffening for street car

Post by panic » Sat Apr 15, 2017 9:35 am


tomhorn1913
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Re: Chassis stiffening for street car

Post by tomhorn1913 » Tue Apr 18, 2017 7:47 am

VERY neat!

Thanks for that link!

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Re: Chassis stiffening for street car

Post by BirdMan » Tue Apr 18, 2017 10:15 am

These were used drag racing, the 64 still is with a 412 9.5 deck w/C4 trans. My 65 will go back to street, hopefully in the near future, like this year!

On 3 Falcons, a 62, 64, 65. I ran 2x3 .120 wall connectors straight back from front stub cutting through rear passenger footwell, moved the rear springs inside of front spring mount, bent rear of connector to be a thin two layer and used original bolt. I cut rear frame section at top crossmember and switching sides the rear hanger was in right position for rear spring location. Added some sheetmetal to outside floor and down to welded lip.

Installed 8 point roll bar with angled brace welded to connector just ahead of rear seat wall on floor. Rear braces to top of rear crossmember. Bolted front support to firewall about 12" up to front body/fenderwell point close to bottom of dash.

I removed this roll bar and installed in son's 64 and is still in it. I made a 10 pt cage with swing Down bar removing the front pin to enter. The forward down bar is just ahead of door opening, away from kick panel to be able to remove it, adding flat plate on floor and door sill per NHRA S/St rules at that time, now a roll bar is okay to 9.99 so we run 10.20's.

I use the latest rollbar padding on side bar and head points. I also will be adding a swing down side bar on passenger side and padded all over also.

We ran stock gas tanks, mine had a bend in to clear the left spring shackle.

My engine will be SBF 347 hopefully with 550/600 hp n.a. Either a 5 spd or C4 auto.
Dale C.

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Re: Chassis stiffening for street car

Post by j-c-c » Wed Apr 19, 2017 11:42 pm

german4inline wrote: It´s very difficult and inappropriate to connect the roof tubing with the rear leaf spring fix point what is not even necessary to my opinion. I would support the bent area of the frame above the rear axle with two tubes leading to the roof tubing, maybe in the rear damper fixing area.
A. The "difficult" part is I suspect more a matter of opinion, and would not be mine, when say dealing with my leaf spring early Mopars.
B. Since I believe most of us can agree all forces acting on the rear tire contact patches pass pass thru, on a leaf spring car, the 4 leaf spring mounting points as they connect to the unibody, and some forces are also directed thru the shock upper connections. On a asymmetrical Mopar leaf spring, I would surmise the front leaf spring restrained mount (vs the rear pivoting mount) bears the brunt of those forces. The "bent area" you mention pretty much only deals with crash loads, those forces transmitted by the longer leaf leaf segments on pivoting mounts (ie much reduced), and any chassis mass (bumper, sheet metal, fuel tank, etc) rearward of the front mounts, and the before mentioned shock loads. I'd be curious how you might explain how that tying the front leaf mounts into any cage structure "is not even necessary", in your opinion.

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Re: Chassis stiffening for street car

Post by BobbyB » Fri Apr 21, 2017 9:13 pm

Hi Tom,
Sounds like you are getting ready for some fun. I have had a 63 Comet hardtop v8 car since 1986. Since then I have street driven it about 20,000 miles, drag raced a few times & autocrossed it a few times. It has a mild 302 with nitrous & c4 with shift kit. Over the years I have done underide traction bars, 3.25,4.11,3.00 & 3.55 axles. The original 8" was upgraded to an 8.8 axle. I have used only open and traction lock differentials. The front suspension is basically like a Shelby mustang. The rear suspension is a centered 3 link with coilovers and watts link. It has 4 wheel disc brakes. I have only used street tires on my car, never slicks or racing tires (I plan to try some toyo r888 tires soon).The last and very recent change to the car was adding subframe connectors. They added 62 pounds to the car. I think I can tell the difference in a spirited drive in the twisties or a straight launch, but just barely. They might make the car safer. If you are only going to use street tires and stock suspension points you can have a nice car and much fun without subframe connectors or a cage. In terms of seat of the pants feel, they do not compare to the other performance changes I have done to my car. Good luck with whatever you decide to do.

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Re: Chassis stiffening for street car

Post by j-c-c » Sat Apr 22, 2017 4:49 am

"They added 62 pounds to the car. " :shock:

That sounds excessive, suspect just that amount of weight and its location, would have a handling impact, even if they were just taped on.

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Re: Chassis stiffening for street car

Post by BobbyB » Sat Apr 22, 2017 10:23 am

I agree, 62 pounds is excessive, but that's what I ended up with. The frames are made from 2x2x1/8 sq tube, 1x1x1/8 sq tube & 3/4x3/4x1/8 angle. They tie the rockers to the torque boxes to the subframes and the floor. My wife just told me I spent the last 4 months working on my car (making subframe connectors) so I need to do some stuff around the house.

The OP asked for input specifically about a 64-65 falcon hard top. The hard top falcon & comet were introduced in mid 63 and lasted through 65. He is concerned about the missing bpillar causing a lack of rigidity. My comet is almost identical to a falcon except it has a longer wheelbase, so my comet is less rigid than a falcon (unless there are some differences in the floor or something subtle) (I would love to compare side by side).

I got my comet in 1986 when I was 25 years old (paid $100.00). My idea of fun has been to see how close to a mustang gt, iroc z, or corvette I could get with sweat equity instead of money. That is what hotrodding is to me. The op says " daily driver, street tires, stock suspension locations." Based on my experience over 31 years of fooling around with a car almost identical to his, subframe connectors would be way down the list in terms of things he needs to do. On the other hand, if he has to do any work on the floor of the car because of rust he might as well do subframes while he is at it. I believe a cage would be way overkill, but I have never driven a street car with a cage.

Op, do you own a falcon yet? I hope you enjoy your falcon as much as I have my comet.

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Re: Chassis stiffening for street car

Post by tomhorn1913 » Sun Apr 23, 2017 6:05 pm

Bobby,

Last question first. Nope. I drove 800 miles last month to look at a pair of '64s. When I arrived, the one I would have purchased was no longer for sale, & the back-up car wasn't quite up to the firm price (in MY opinion anyway). I've missed a couple likely candidates in the past month, but I'm still optimistic.

Your speculation is good. I'm figuring that I will likely need to replace most or all of the floorpan when I find my car. I'm not interested in spending a ton of money for a real nice car, just to rip into it & change everything (been there, done that, doesn't make $ sense). A 50+ year-old unibody car is probably going to have floorpan issues. That's the reasoning behind my intent to make the chassis a sturdy foundation, so all the other enhancements give maximum benefit. I'll buy the basics, & spend the big money on making things just the way I want them.

Who knows - perhaps my grandson will be a gearhead, too?

Peace,
Matt

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Re: Chassis stiffening for street car

Post by pdq67 » Tue Apr 25, 2017 7:33 pm

People,

Do you know why the Henry-J's were used vs the 3/4 sized '50 Ford looking , Willy's Aero Eagles??

The Henry J's had full frames whereas the Willys is a full uni-body car.

pdq67

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Re: Chassis stiffening for street car

Post by panic » Mon May 08, 2017 4:25 pm

re-designing the floorpan as a backbone chassis

I'm not sure it's that complicated.
An 18 gauge half-tube replacing (or doubling) the existing d-shaft tunnel, running into the front of the transmission bellhousing flare (under the dash) and back to the axle kick-up can be installed by simply SawzAll right through the floor. Miss the seat depressions, existing pan stiffening areas etc. as appropriate. Choose the tube OD by the width of the cut - 8"? 10"? A single tube cut accurately lengthwise along the centerline allows the 1/2 lengths to be used end-to-end. The lengthwise cuts can be slightly angled to produce tapers to offer more clearance.
This may also allow you to raise the tailshaft and driveshaft up into the curve to have more choices for vertical and lateral transmission alignment and rear spring arc.
This will stiffen the floor against bending in pitch and yaw, but the torsional stiffening will be a function of the cube of the tube's diameter (IIRC) so make it as large as practical. Extra wall thickness obviously helps (and the weight is harmless), but not as effective as increased OD for stiffness, and thickness much greater than the floor makes welding more difficult.
Yes, you may discover important structures in/near/under the floor that make this more difficult, but I'd certainly inspect it.

Nice project, best of luck with it!

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Re: Chassis stiffening for street car

Post by tomhorn1913 » Sat May 13, 2017 2:01 pm

panic,

Very interesting train of thought. Especially if the project requires floorpan repair. Rather than patch a floor with multiple areas of rust-through, cut it all out. Buy a full replacement pan, mock it up for measurements, them remove and fab your backbone tunnel. Having the floor out, where you could flip it, and access all angles, you could achieve the best possible fitment. Welding would be SO much easier! Neat idea!

Thanks,
Matt

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Re: Chassis stiffening for street car

Post by n2xlr8n » Thu May 25, 2017 9:35 am

This guy just built a 62 and performed some of chassis mods you refer to.

His blog is hilarious. You'll have to find the specific post, but it's worth the read when one has time.

http://ironhydroxide.blogspot.com/2013/ ... r-you.html
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Re: Chassis stiffening for street car

Post by Jeff Lee » Sun May 28, 2017 11:38 pm

I have no experience in this but if it were my project, I would put in a CM subframe connector intersecting the floors and welded floor to connector. I would use CM on any / all parts added. I would stitch weld all factory weld points along the entire length of the seam. I would take a look at Kenny Brown Mustang Suspensions and integrate his under floor frame to your Falcon (use his ideas, not his parts as I’m sure none are interchangeable). I would seriously look at a late Mustang IRS as they are dirt cheap, you get a good suspension, gears and brakes. Then do what you can afford on the front suspension; Shelby or better if in your budget. Then good tires and front seats.
At that point, you maybe very happy with the car. If not, you haven’t done anything that needs to be removed, just build from there.
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Re: Chassis stiffening for street car

Post by BobbyB » Tue May 30, 2017 11:50 am

Jeff, Why do you think the IRS would be better than a 3 link with a solid axle?

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Re: Chassis stiffening for street car

Post by Jeff Lee » Fri Jun 02, 2017 11:47 pm

Hmmm... my response went missing. I don't know if one is better than the other. I'm a drag racer not a road racer but I know Ford spent tens of millions of dollars in R&D on the Mustang IRS and we now have a world class Mustang.
And plenty of aftermarket support to handle anything you can probably throw at it.
My son has an '01 Mustang GT and we've been hitting the wrecking yards and some fab shops and find plenty of IRS units. Some pulled to swap to drag race solid axles. But it seems you can buy one for less than $500.
It just seems to me this would be a great foundation and would provide uniqueness. Obviously not a bolt in but doesn't seem beyond your abilities from what I'm seeing here.
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