Gran Fury: Cutting some frame rails and relocating some leaf springs

[mattechperf]

I'm moving along with modifying the back end of my 88 Fury. I thought I'd sure some work and outline my thoughts.

The plan was to widen the wheel tubs and trim the sheet metal on the outer frame rails. All lot of room can be had without doing a complete back-half.

This led to the leaf springs needing to move inward. Well, that seems to be easy on the other Mopar platforms, but the M-body at least needs to go all the way to the other side of the frame rail. This will move them inward about 8 inches per side.

I'm building a new crossmember similar to a front mount of a ladder bar or 4-link setup, but will support the front leaf spring mounts. I'll use some 2x5" 0.120" wall square tube and a pre-made driveshaft loop from QuarterMax.
It'll bolt to the OEM spring mounts (for alignment) and will get welded into the stock frame and floor pans. This will also make a great pace to weld frame connectors to going forward under the car.

After talking with Calvert Racing, I'll go to one of their Caltrac traction bar setups and replace the rear shackles with sliders from Speedway Motors. They'll be a tad more noisy, but I plan on making plenty of noise anyway.
I'll build a few brackets to mount to the original rear spring shackle mounts on the frame and some DOM tubing will span across that where I can mount new brackets for the rear shackle/slides.
The trunk floor will definitely be in the way, but I plan on a fuel cell anyways. So, some cutting will be happening. I apologize to the purists in here.

I'm just starting on the fabrication process and need to get my nerve up before cutting the frame. Lots of measuring and re-measuring happening over the next week.
This is getting exciting!

 

[Oldiron440]

The front half of the wheel housing's are a limiting factor on your car or an Fbody, I have 30 x 10.5s on my Fbody with the limiting factor being the inner front wheelhouse.

 

[mattechperf]

The front half of the wheel housing's are a limiting factor on your car or an Fbody, I have 30 x 10.5s on my Fbody with the limiting factor being the inner front wheelhouse.

Yes, that looks to be tricky. What did you do to get the clearance in that area? Did you just cut it out?

 

[Oldiron440]

I got by with a hammer at the time but I would mini tub it now. Part of my problem was I was trying to get the largest tire in without tubbing it, I wanted stock rails also. The wheel openings have pie cuts on the front of the openings..
I had other plans for the car that included salt and a stocker type 360 but that's not going to happen.

 

[XfbodyX]

How big of tire are you shooting for? Its a simple process, cardboard and crayon could get it done. While your doing it move the axle back to get away from the front pinch.

 

[Oldiron440]

The one thing that I would consider doing is running the leaf springs parallel opposed to the factory layout if your building a drag car.

 

[mattechperf]

How big of tire are you shooting for? Its a simple process, cardboard and crayon could get it done. While your doing it move the axle back to get away from the front pinch.

That's an excellent point about locating the axle. I'm swapping in a Ford 8.8, so I'll be able to properly locate that guy a little farther back.

 

[mattechperf]

The one thing that I would consider doing is running the leaf springs parallel opposed to the factory layout if your building a drag car.

Yes, good idea. I explored the method of spreading the leafs outward in the back a little to help with lateral stability.
However, I'll have solid mounts in front and solid sliders in the back. I'll build it parallel and if I still have any lateral movement, I'll build a panhard bar or something.

 

[XfbodyX]

I asked about tire width as it sounds like if going wide? Removing the factory rails and just putingt a simple set of frame rails is easy to on that pan setup.

Dont over think this, its simple.

 

[Oldiron440]

You can always move the factory rail's in...
If you were to do this the inner wheel housing's could move in also so you could mini tub it...
The floor between the wheelhouse are flat if I remember correctly but farther back you have the spare tire well but that should go away anyhow.

 

[XfbodyX]

I like simple, if your gonna go wide on a car that dont matter, cut it, gut it, fab it new.

 

[Oldiron440]

Not everyone wants a back half car but they do have their benefits if you need a big tire. But big tires use up horsepower.

 

[XfbodyX]

ok.

 

[BudW]

While your doing it move the axle back to get away from the front pinch.

How far back would you locate the rear differential?

 

[XfbodyX]

Id have to look, I think its dead on 1 inch, calvert springs make it easy as at least mine when you seperate the small clamps on them there are holes to move them 1 inch up or back. If your using a aftermarket D shaft the way they have you measure "for me left enough spline engagement" but you must check the actual engagement in the inner yolk as they vary. But Im able to use the same yolk. It sorta put my spring sliders at the very end of acceptable sitting stance but they still worked. If I ever use sliders again I will make them bolt vs weld on so they can be used with any spring and ones that settle, calverts will settle a bit over time also.

 

[Oldiron440]

That's one of the reasons why I haven't committed to spring sliders on my Fairlane yet, it seems that placement needs to be dead on or you risk binding the springs.

 

[mattechperf]

I asked about tire width as it sounds like if going wide? Removing the factory rails and just putting a simple set of frame rails is easy to on that pan setup.

Don't over think this, its simple.

I'm not going super huge. I'll probably end up with a 295 or 315 at the most.
Since I'll be doing a decent amount of driving, I don't want to set this up so it only fits a $350-$400 tire. I plan on LOTS of burnouts.
But, I at least want to get a decent drag tire in there when I need it.

The axle width will be set at around 1-7/8" narrow per side. So, I'll mock up the rim offset once that's put in place and see how tall I really want to go.
I want this to sit nice, not super low, but nice. I'm fussy about how a wheel/tire combo fits in a wheel well and how it fits the overall look and proportion of the car.
22's were fine on my Chrysler 300, but NOT on a Gran Fury.

 

[mattechperf]

Id have to look, I think its dead on 1 inch, calvert springs make it easy as at least mine when you seperate the small clamps on them there are holes to move them 1 inch up or back. If your using a aftermarket D shaft the way they have you measure "for me left enough spline engagement" but you must check the actual engagement in the inner yolk as they vary. But Im able to use the same yolk. It sorta put my spring sliders at the very end of acceptable sitting stance but they still worked. If I ever use sliders again I will make them bolt vs weld on so they can be used with any spring and ones that settle, calverts will settle a bit over time also.

This is great info. Since I'm going to be fabbing new stuff all around, now's the time to optimize these things.
And, you make a great point about yoke spline engagement. There's usually a little wiggle room, but I've seen too many people dismiss this and wonder why they pole-vault their car 60ft out of the hole.
I was on the fence about how I mount my sliders, but I think you've convinced me to make a flange they can bolt to vs being welded directly. Good stuff.

 

[Duke5A]

A 285 on a 9.5" rim fits inside unmolested fenderwells on my car. Seems like a lot of work for just going up to 315 at max.

Would getting it to the track first to see if wider tires are needed first, or would this just lead to potentially having to do a lot of things twice?

 

[mattechperf]

A 285 on a 9.5" rim fits inside unmolested fenderwells on my car. Seems like a lot of work for just going up to 315 at max.

Would getting it to the track first to see if wider tires are needed first, or would this just lead to potentially having to do a lot of things twice?

Sometimes, the work is just to prove to myself I can do it or it can be done.
And further more, the cutting has begun!