1974 Roadrunner Re-Paint and Some Upgrades

[DeltaV]

and torsional stiffness is to the 4th power of the diameter.

That doesn’t seem like much of a difference.

See my comment above. Ergo, it does make a difference...it will be noticeable.

That small amount of difference seems to me that there will not be a noticeable effect

See my comment above. Ergo, it does make a difference...it will be noticeable.

Look up torsional spring stiffness and notice the J (or I) term with d to the 4th power. You can algebraically compare the effect of going to a different diameter.

Or, take Matt's advice.

I’m guessing since it was originally a RR 318 car

I believe I and others were under the impression your car is a factory 440 car.

***
Just a comparison, the torsion bars on my B-body '79 300 heavy duty suspension have a diameter of 0.98"; and the same 43.6" length as your car. Ergo, my car has the same torsion bar dimensions as a '74 RR with the 440. Furthermore, checking my documentation, mine are the same part numbers as the '74 RR 440.

My 360-4V engine is lighter than your 440-4V. I would go with the 1.06" diameter torsion bar for your car since our B-body cars are similar (not similar in appearance).

 

[RR Fan Dan]

I believe I and others were under the impression your car is a factory 440 car.

No it was originally a 318 manual on the floor 3 speed RR. It was changed to a 440 manual 4 speed. I wish it was a factory 440. That would make it a rare 74 GTX.

 

[RR Fan Dan]

What’s ergo?

 

[DeltaV]

What’s ergo?

Shorter version of therefore.

 

[RR Fan Dan]

Shorter version of therefore.

Okay now your post makes sense to me. So you think the 1.06” is the smart choice? I was doing the the math comparing to the size of the sway bar I’m getting and the sway bar is bigger (1.125”), so maybe 1.06” would be fine. It’s the middle pick on their site too.

 

[RR Fan Dan]

A typo somewhere? Which diameter front sway bar are you going to use?

Did you tell Matt you ordered a 1" rear sway bar from Addco?

What does Matt recommend for front and back sway bar diameters?

It is 1 1/4” sway bar. My confusion is it is listed as 1 1/8” on the Firm Feel website, but Matt told me 1 1/4” over the phone. I just got the invoice from Matt and it is listed as 1 1/4” on the invoice. I corrected this thread.

 

[WileE]

What’s ergo?

Shorter version of therefore.

It's when you dump your wife or girlfriend. You say " I let ergo."

 

[YY1]

As noted above- the soft, rubber "ISO" biscuits started in 73 on B body cars.

If it were me, I'd replace those with at least the poly biscuits if not the metal ones.

Kind of hard to find, but takes away some of the "squish" and brings back more of the traditional B body feel.

 

[RR Fan Dan]

As noted above- the soft, rubber "ISO" biscuits started in 73 on B body cars.

If it were me, I'd replace those with at least the poly biscuits if not the metal ones.

Kind of hard to find, but takes away some of the "squish" and brings back more of the traditional B body feel.

You mean like these? Firm feel has them and the body mounts. I’m on the fence about using them. Most all of comfort will have been removed and upgraded with HD and urethane. I don’t want an entirely rigid ride. I’m thinking about leaving the rubber isolators in place.

 

[DeltaV]

Okay now your post makes sense to me. So you think the 1.06” is the smart choice? I was doing the the math comparing to the size of the sway bar I’m getting and the sway bar is bigger (1.125”), so maybe 1.06” would be fine. It’s the middle pick on their site too.

View attachment 1946799

Yes, I would go with the 1.06" dia. torsion bars.

 

[DeltaV]

I was doing the the math comparing to the size of the sway bar I’m getting and the sway bar is bigger (1.125”), so maybe 1.06” would be fine.

I'm not sure why you're comparing a sway bar diameter to a torsion bar diameter.

 

[DeltaV]

It is 1 1/4” sway bar.

So, you'll have 1-1/4" up front and 1" out back.

Good.

 

[RR Fan Dan]

So, you'll have 1-1/4" up front and 1" out back.

Good.

Actually when you said that I looked at my Jegs order for the rear to confirm. It's actually 3/4”, according to the description on the order. It won’t show me product details because it is out of stock. I think I bought the last rear sway bar in the country for a 74/74 b body.

 

[DeltaV]

If it were me, I'd replace those with at least the poly biscuits if not the metal ones.

Totally agree.

I’m thinking about leaving the rubber isolators in place.

No. At a minimum, go with the poly biscuits.

 

[DeltaV]

It's actually 3/4”

You've been throwing out a lot of wrong numbers lately.

A 3/4" rear sway bar is good too.

 

[DeltaV]

So, what are you doing with the leaf springs and associated mountings?

 

[RR Fan Dan]

You've been throwing out a lot of wrong numbers lately.

I know, I’ll try to get better. Like I said Jegs won’t let me see the details page so I pulled what I thought was the same kit I bought off another site. Apparently it came in different sizes. Or maybe it didn’t. I was so happy when I found it I just hit buy and didn’t pay much attention to what size it was and now Jegs won’t let me go back and see what I bought. This is all I get for a description. When you click the link it says item not available.

 

[DeltaV]

I know, I’ll try to get better. Like I said Jegs won’t let me see the details page so I pulled what I thought was the same kit I bought off another site. Apparently it came in different sizes. Or maybe it didn’t. I was so happy when I found it I just hit buy and didn’t pay much attention to what size it was and now Jegs won’t let me go back and see what I bought. This is all I get for a description. When you click the link it says item not available.

Picture with home address deleted.

I deleted your picture. Blot out your personal info (name and address) and add it to your reply above.

 

[RR Fan Dan]

I'm not sure why you're comparing a sway bar diameter to a torsion bar diameter.

Just as a reference.

So, what are you doing with the leaf springs and associated mountings?

Nothing yet. I figured the RR got the HD so they would be fine.

 

[RR Fan Dan]

Totally agree.


No. At a minimum, go with the poly biscuits.

Won’t that make my teeth rattle