73/74 RR Torsion Bar Question and Opinions

[HawkRod]

I got those as well, so I will probably stay with the rubber iso bushings on the body and cross member. After all one of the big selling points for the 73/74 was the new quieter smoother ride. Nice car BTW.

I want to recall that when I went to replace the bushings the only type available were polyurethane. If I had my pick, I'd choose polyurethane over rubber anyway, and understand that comment is coming from a guy who mostly prefers rubber in his suspension components. My rubber bushings had the life squeezed out of them, and I think polyurethane will handle the stress much better while still providing some isolation.

 

[1 Wild R/T]

I got those as well, so I will probably stay with the rubber iso bushings on the body and cross member. After all one of the big selling points for the 73/74 was the new quieter smoother ride. Nice car BTW.

If your using sub frame connectors rubber isolators is 100% the wrong choice....Either Solid mounts (best choice) or urethane...

The Subframe connectors purpose is to prevent flex... Solid mounts prevent flex... Rubber especially old rubber flexes.... Get rid of it...

Personally I would get the Bilstiens for the front & modify as needed...

 

[DeltaV]

No they don’t match up. Here is the 0.75 bar I got on their website.

View attachment 1947178

They also have a 1” that fits my car. That’s what caused all the confusion on what size I actually got from Jegs, cause I couldn’t cross reference the Jegs part number. Dang Jeg Cofflin, I like Mike Anderson better but his website is slow.

View attachment 1947182

My bad. I had too many windows open and was bouncing back an forth. That's my excuse and I'm sticking to it.

I should have attached a screenshot and gotten it right.

Jeg's p/n: 020-290 for the 1" rear bar

 

[RR Fan Dan]

coming from a guy who mostly prefers rubber in his suspension components

If your using sub frame connectors rubber isolators is 100% the wrong choice....Either Solid mounts (best choice) or urethane...

Now I don’t know what to do. I wouldn’t think a few rubber isolation bushings on the body and cross member are going to cancel out all the other suspension upgrades. Bigger torsion bars, better Upper Control Arms, bigger front sway bar, reinforced LCAs, subframe connectors, firmer steering gear box. Urethane bushings in front and rear sway bars, upper control arms. Bilstein shocks in rear. All new ball joints, tie rod ends, adjusters, pitman arm, idler arm, etc.,

It’s gotta be way better than it was.

 

[HawkRod]

Now I don’t know what to do. I wouldn’t think a few rubber isolation bushings on the body and cross member are going to cancel out all the other suspension upgrades. Bigger torsion bars, better Upper Control Arms, bigger front sway bar, reinforced LCAs, subframe connectors, firmer steering gear box. Urethane bushings in front and rear sway bars, upper control arms. Bilstein shocks in rear. All new ball joints, tie rod ends, adjusters, pitman arm, idler arm, etc.,

It’s gotta be way better than it was.

You have to read my full comment. I said to get polyurethane. My comment "coming from a guy who mostly prefers rubber in his suspension components" is intended to strengthen the suggestion to get polyurethane (or even solid).

 

[1 Wild R/T]

Now I don’t know what to do. I wouldn’t think a few rubber isolation bushings on the body and cross member are going to cancel out all the other suspension upgrades. Bigger torsion bars, better Upper Control Arms, bigger front sway bar, reinforced LCAs, subframe connectors, firmer steering gear box. Urethane bushings in front and rear sway bars, upper control arms. Bilstein shocks in rear. All new ball joints, tie rod ends, adjusters, pitman arm, idler arm, etc.,

It’s gotta be way better than it was.

From Post 38...

In my 73 Road Runner, I replaced the rubber bushings with polyurethane. Part of me wants to be cautious about using steel inserts to replace them, but then again, my 70 is mounted solid to the body and I have no issues.

At any rate, when I drove my 73 cross country both ways it drove and handled nicely with the polyurethane busings. But quite frankly, I believe one of the best improvements in ride is to stiffen the chassis with subrame connectors, etc.


So my point is as Hawk stated removing flex is the key to making the suspension actually work... You want predictable compliance from the suspension and a rock solid platform to attach that suspension to...

That predictable compliance comes from well designed shocks springs & sway bars...

There are different theories on handling

Some prefer beefy springs/sway bars & heavily valved springs

Others prefer moderate springs, big sway bars & well designed shocks... For a street car this is my preference..

Your 1' rear bar & 1.25" front bar definitely qualify Only question is frt/rear balance

 

[HawkRod]

^^^ What he said!!!

 

[DeltaV]

Now I don’t know what to do. I wouldn’t think a few rubber isolation bushings on the body and cross member are going to cancel out all the other suspension upgrades. Bigger torsion bars, better Upper Control Arms, bigger front sway bar, reinforced LCAs, subframe connectors, firmer steering gear box. Urethane bushings in front and rear sway bars, upper control arms. Bilstein shocks in rear. All new ball joints, tie rod ends, adjusters, pitman arm, idler arm, etc.,

It’s gotta be way better than it was.

I know it's a gross oversimplification, but I'm going to say it's anyway. It's like three springs mounted in series...(1) steel K member and all the suspension stuff, (2) rubber isolator, and (3) steel body. You have beefed up two of the springs and still have one relatively soft spring. The effective spring of all three is still "soft" and your old one is really soft. You need a stiffer isolator by going with a urethane or metallic isolator material.

1/k effective=1/k1 + 1/k2 + 1/k3

Sure, the factory used those isolators to reduce road noise and vibration. However, I bet modern radial tire and shock absorber (damper) technologies are a vast improvement over what they used in 1974.

Replace your old rubber isolators with metallic ones.

 

[DeltaV]

Your 1' rear bar & 1.25" front bar definitely qualify Only question is frt/rear balance

He now says 3/4" bar, but yeah balance. Test drive.

 

[RR Fan Dan]

My bad. I had too many windows open and was bouncing back an forth. That's my excuse and I'm sticking to it.

I should have attached a screenshot and gotten it right.

Jeg's p/n: 020-290 for the 1" rear bar

View attachment 1947194

This is the one I got only for $16 less a few weeks ago.

 

[1 Wild R/T]

He now says 3/4" bar, but yeah balance. Test drive.

I'd rather have to much front bar than to much rear bar....

To much rear bar is fun if you have the skills and are paying attention... If not you can be in over your head quickly... Cars set up that way are tail happy... So you've gotta be ready to countersteer if the back end gets loose.. If you drive on ice much it becomes second nature...

To much front bar doesn't do much, till you push really hard then the front end will push, but unless you ignore the signs it won't do anything scary...

Well, as long as the tires aren't from the seventies... Good old Michelin XZX's... Once they started sliding they kept sliding till the car damn near completely stopped.... Terrifying...

Normal tire even back then would squawk & squeal, slip out a little but mostly maintain control.... Not the XZX... Grip, Grip ,Grip... SSSSSSllllliiiiddddiiinnngggg

 

[RR Fan Dan]

To much rear bar is fun if you have the skills and are paying attention... If not you can be in over your head quickly... Cars set up that way are tail happy... So you've gotta be ready to countersteer if the back end gets loose.

I’m glad I didn’t get the 1” now. Not that I can’t handle a tail happy car, I’d rather not have it breaking loose every time I romp on it. Plus I am rebuilding the motor too, and I won’t be happy with anything less than 600hp. At least that’s my target, but I’m not ready to think about that just yet. The motor is out and at the shop. It hasn’t been torn down yet so I’ll worry about that later. Right know I am concentrating on the suspension for when the car goes back together. Little things like aluminum isolators are an easy replacement now. Not so much if the car gets back together and I decide I wanted to switch them out.

 

[RR Fan Dan]

So Matt at Firm Feel wants to thank you guys for increasing his revenue stream today. He highly recommends the aluminum isolators, so they have been added to the invoice.

 

[HawkRod]

IPlus I am rebuilding the motor too, and I won’t be happy with anything less than 600hp. At least that’s my target, but I’m not ready to think about that just yet.

I build engines with my father-in-law now that I am retired (and he built stuff for Kenny Montgomery and worked with Grumpy Jenkins). Trust me when I say that for a street engine you want to build an engine for broad, low end torque. It's a big over simplication, but high RPM horsepower does not matter - you will seldom use that on the street. Lots of low end torque WILL be used on the street and will make your car a pleasure to drive. My 70 Road Runner makes 675 lb ft of torque. On the 2023 Hot Rod Power Tour I got 16.9 MPG on the highway doing 75 MPH average speeds. It is an awesome engine.
Bottom line is talk to your engine builder about goals and how you intend to use your car. Many times, owners will put wild cams and high compression pistons (and more) into an engine and end up with a finicky race engine that runs like crap on the street and needs race fuels to work. Target 10:1 compression max and a roller cam that makes good torque, along with heads that breathe well.

Good luck!

 

[RR Fan Dan]

Lots of low end torque WILL be used on the street and will make your car a pleasure to drive.

I didn’t forget about the torque. I want the torque to be right in line with HP. My engine builder has a Cutless 442 with a 455 making 1000 Tq. I’m sure he can help me in this department.

 

[1 Wild R/T]

So Matt at Firm Feel wants to thank you guys for increasing his revenue stream today. He highly recommends the aluminum isolators, so they have been added to the invoice.
View attachment 1947214View attachment 1947215

I love spending other people's money...

 

[RR Fan Dan]

I love spending other people's money...

I see that. I’m gonna have to put you on ignore, you’re costing me too much.

 

[Nacho-RT74]

I’ve been working with Matt at Firm Feel to upgrade the suspension on my 74 RR. We are discussing the front torsion bar and he initially recommended a 1.06” replacement bar. I told him I wasn’t racing and I asked him if that would make the ride hard and bumpy. And also asked him what the stock diameter bar was. He said the stock bar was maybe 0.92” and maybe the 1.00” would suit me better. I am looking for opinions and suggestions as what to go with? Is my stock bar 0.92” and will another 0.08” (1.00” bar) make a difference, or should I jump to the 1.06” bar for a 0.14” increase? Or should I keep it stock? The upper control arms are being replaced with Firm Feel, the lower control arms are stock but will have reinforced bars added. A 1-1/4” Firm Feel sway bar kit is also being added.

Just barelly noticed this thread. Won’t read all the thread but just share my experience.

I got the 1.06 from FF and that allowed me a lower ride height with about about same stock stiffness. Lower ride height with stock bars would make it bounce a lot. But the spring rate is also related to the weight to hold. 1.06 for big block, never for small block

The stiffening ride is not just the T-bars… needs to be accompanied with higher compression Shock Absorvers. And 73/74 got a small chart of options for that.

When money is enough I’ll go with RCD (Bilstein) shocks. Right now I have the only KYB option for us in front… nothing more that around the same stock specs, but on a quality brand.

On a side note… I kept the stock Big Block sway bar (15/16” I think it is?, but NOS.