1974 Roadrunner Re-Paint and Some Upgrades

[DeltaV]

Won’t that make my teeth rattle

Don't select really "stiff" shocks if you're concerned about rattling your dentures.

Matt should be able to help guide you with the shocks for your setup.

 

[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.

View attachment 1947144

The Addco website will tell you what diameter for their p/n 20-236. That's their part number.

 

[RR Fan Dan]

Don't select really "stiff" shocks if you're concerned about rattling your dentures.

Matt should be able to help guide you with the shocks for your setup.

I got the Bilstein RCDs for the rear. I had them on my 68 and liked them. For the fronts I got the KYB excels, because the LCAs needed to be modified to fit the matching Bilstein for the front.

 

[DeltaV]

I figured the RR got the HD so they would be fine.

Not sure what you mean. Your car originally had a 318 and now has a 440. Was the rear axle and suspension changed with the engine change? Prop shaft came from a what?

 

[RR Fan Dan]

Not sure what you mean. Your car originally had a 318 and now has a 440. Was the rear axle and suspension changed with the engine change? Prop shaft came from a what?

All RR got the upgraded HD leaf springs. Remember in 74 the RR was a satellite option, not a stand alone.

 

[RR Fan Dan]

Prop shaft came from a what?

I’m not sure what this means.

 

[RR Fan Dan]

Was the rear axle and suspension changed with the engine change?

All RR in 74 got the 8.75. Stock axle. Gears were changed to 4:10’s, probably going back to 3:23 or 3:55. Depends on motor rebuild.

 

[DeltaV]

I’m not sure what this means.

Sorry...driveshaft.

"Prop shaft" is in the FSM and other factory documentation.

 

[HawkRod]

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.
View attachment 1947105

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.

 

[RR Fan Dan]

The Addco website will tell you what diameter for their p/n 20-236.

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

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.

 

[RR Fan Dan]

But quite frankly, I believe one of the best improvements in ride is to stiffen the chassis with subrame connectors, etc.

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.

 

[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.