[Moxx]

Long story short, I just came into possession of a 351w and I’m looking to put it into a ‘71. I’m working on my budget, and noticed that I’d need an entire suspension subframe in order to put coilovers in the rear. I’m not looking to race this, I just want it to drive well, so I can live with leaf springs, but I won’t be happy about it.

My first question, is there anything I can tear the rear suspension out of instead of dropping $3-4000 on a suspension kit? Or, in your opinion, what’s the best alternative to make the rear suspension more sportier without the huge cost for a suspension kit?

 

[Beechkid]

Long story short, I just came into possession of a 351w and I’m looking to put it into a ‘71. I’m working on my budget, and noticed that I’d need an entire suspension subframe in order to put coilovers in the rear. I’m not looking to race this, I just want it to drive well, so I can live with leaf springs, but I won’t be happy about it.

My first question, is there anything I can tear the rear suspension out of instead of dropping $3-4000 on a suspension kit? Or, in your opinion, what’s the best alternative to make the rear suspension more sportier without the huge cost for a suspension kit?

Sportier is a subjective term....the existing rear suspension was successfully used in drag racing, road racing and street use...... Coil-over for 1) are not going to make the handling of any vehicle magically become "better"... even if you look at 2 link, 4 link set-ups each has disadvantages that requires considerable engineering and $ to overcome.... that is why even when tested with a IRS back in the late 60's the leaf's performed so close to it it was not worth the $ even in the racing forums. Do your springs need to restored to a particular ride height? If so no biggie....a real suspension/spring shop can put them where ever you want using a "Hot" re-arching process (don't use cold because it's a temp fix)... got a bit of sway, time for a sway bar, need to firm it up a tad, get some really good shocks but the system (components) not only must match your needs they have to match the whhel/tire combination you have and the road conditions you are driving on..... (smooth, little rough, pot-holes common, etc.)

 

[Moxx]

Sportier is a subjective term....the existing rear suspension was successfully used in drag racing, road racing and street use...... Coil-over for 1) are not going to make the handling of any vehicle magically become "better"... even if you look at 2 link, 4 link set-ups each has disadvantages that requires considerable engineering and $ to overcome.... that is why even when tested with a IRS back in the late 60's the leaf's performed so close to it it was not worth the $ even in the racing forums. Do your springs need to restored to a particular ride height? If so no biggie....a real suspension/spring shop can put them where ever you want using a "Hot" re-arching process (don't use cold because it's a temp fix)... got a bit of sway, time for a sway bar, need to firm it up a tad, get some really good shocks but the system (components) not only must match your needs they have to match the whhel/tire combination you have and the road conditions you are driving on..... (smooth, little rough, pot-holes common, etc.)

I was thinking of just purchasing new leaf springs and shocks for the rear, and getting both front and rear sway bars. That’d be fine in your opinion?

 

[crjackson]

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[Beechkid]

I was thinking of just purchasing new leaf springs and shocks for the rear, and getting both front and rear sway bars. That’d be fine in your opinion?

Re-arc springs done correctly will be much $ saving and then let's say you want the car a bit lower, with the rear say 1-2" lower, the shop can set them for that height and they will stay there for a few decades... and you actually know what you have (as compared to are they made in China or ?)!

Increasing the front sway bar... a very good idea! Rear sway bar, wait until you get your front SB and shocks on first and drive the car. In the road racing circuits (such as SCCA), the closer to stock classes didn't run rear SB's as they needed the little bit of extra "give" to keep the rear firmly planted..... my own mustang, I do run front & rear bars, but my rear one is fully adjustable and is set (after much trial & error) to a very 'loose" setting and it does just fine.

with regards to shocks.....IMHO:

1) Koni- Excellent for racing applications- overpriced for street applications

2) Tokico, QA1 & Bilstein- A very good shock for street/strip applications, but QA1 & Bilstein have had periodic QA issues!. If you are running very stiff tires on the street (such as Bridgstone or tires with profiles shorter than 50 series), these provide the extra give that you need for both comfort & stability

3) KYB- A very good shock for street/strip applications. If you are running softer tires on the street (such as BFG or tires with profiles not shorter than 50 series), these provide the extra stiffness that you need for both comfort & stability. The Exel-G’s (formerly GR-2) are the equivalent to the Edelbrock IAS automatic adjusting units. Overall, stiffness between the Gas-a-just and the GR2’s are the same, the difference is the GR-2's valving which stiffens things up from a oem setting to that of the Gas-a-just units but otherwise acts really as a good shock until you start putting demands on the suspension, then they are all there..

4) Gabriel- A very nice good quality HD OEM replacement type unit.

5) Monroe- stay away from that junk!


Hope this helps.

 

[Grimbrand]

Beech nailed it. While there are a ton of very expensive aftermarket kits for rear ends out there, the truth is, if you have a live axle, there is very little difference between the way a set of proper leafs and good shocks feel, vs. coilovers.

The exception to this rule is full independent rear suspension - which isn't cheap. The full independent setups do better going over bumps in a corner, and ride a little smoother, but offer little to no performance gain.

Your best bet is to get the best shocks you can afford. For a cruiser, Bilstein is probably going to be the best choice, IMHO.

Edit: It's worth mentioning that GOOD springs, wheels, shocks and tires do make a tremendous difference. The stock rear springs on these cars are actually very high quality steel, and usually better than what you can get now. Refurbished, cleaned up, and recurved, they work well. Your front suspension has a lot more to do with the overall feel of your ride than the rear - and although it's more complicated, a few basic guidelines can vastly improve that for cheap, too.

Either do the Shelby drop, or get aftermarket control arms to correct the front end geometry. Roller perches if you can afford them, and solid mount adjustable front struts. Get good Bilstein shocks, and maybe some 600-620# variable-rate springs (harder to tune for track use, but they work great on the street!). Use a 1" front sway bar. Do a modern alignment with more caster. 3.5 degrees for manual, and 5 or more for power steering. More caster will increase return-to-center, improve feel, and add high-speed stability. It will also make your wheel a bit harder to turn. The rest of the original settings work well with modern tires; 0- .5 degrees of camber, and 1/16" of toe in on each side so the tires are parallel when you're going down the road.

Welcome to AFM, Moxx!

 

[Moxx]

Re-arc springs done correctly will be much $ saving and then let's say you want the car a bit lower, with the rear say 1-2" lower, the shop can set them for that height and they will stay there for a few decades... and you actually know what you have (as compared to are they made in China or ?)!

Increasing the front sway bar... a very good idea! Rear sway bar, wait until you get your front SB and shocks on first and drive the car. In the road racing circuits (such as SCCA), the closer to stock classes didn't run rear SB's as they needed the little bit of extra "give" to keep the rear firmly planted..... my own mustang, I do run front & rear bars, but my rear one is fully adjustable and is set (after much trial & error) to a very 'loose" setting and it does just fine.

with regards to shocks.....IMHO:

1) Koni- Excellent for racing applications- overpriced for street applications

2) Tokico, QA1 & Bilstein- A very good shock for street/strip applications, but QA1 & Bilstein have had periodic QA issues!. If you are running very stiff tires on the street (such as Bridgstone or tires with profiles shorter than 50 series), these provide the extra give that you need for both comfort & stability

3) KYB- A very good shock for street/strip applications. If you are running softer tires on the street (such as BFG or tires with profiles not shorter than 50 series), these provide the extra stiffness that you need for both comfort & stability. The Exel-G’s (formerly GR-2) are the equivalent to the Edelbrock IAS automatic adjusting units. Overall, stiffness between the Gas-a-just and the GR2’s are the same, the difference is the GR-2's valving which stiffens things up from a oem setting to that of the Gas-a-just units but otherwise acts really as a good shock until you start putting demands on the suspension, then they are all there..

4) Gabriel- A very nice good quality HD OEM replacement type unit.

5) Monroe- stay away from that junk!


Hope this helps.

Wow. Thanks so much for the info! I’m not planning to drive it on the track. Just road use and maybe go to some cruise nights once this pandemic dies down a bit. I’d been looking at some QA1s, but I’ll check out a few others. And when you say 50 series tires, are you talking about the model, right? Not the second number in a tire profile, the one that indicates % of its width in height from the rim.
Thanks again! I can’t express how helpful all this info has been.

Beech nailed it. While there are a ton of very expensive aftermarket kits for rear ends out there, the truth is, if you have a live axle, there is very little difference between the way a set of proper leafs and good shocks feel, vs. coilovers.

The exception to this rule is full independent rear suspension - which isn't cheap. The full independent setups do better going over bumps in a corner, and ride a little smoother, but offer little to no performance gain.

Your best bet is to get the best shocks you can afford. For a cruiser, Bilstein is probably going to be the best choice, IMHO.

Edit: It's worth mentioning that GOOD springs, wheels, shocks and tires do make a tremendous difference. The stock rear springs on these cars are actually very high quality steel, and usually better than what you can get now. Refurbished, cleaned up, and recurved, they work well. Your front suspension has a lot more to do with the overall feel of your ride than the rear - and although it's more complicated, a few basic guidelines can vastly improve that for cheap, too.

Either do the Shelby drop, or get aftermarket control arms to correct the front end geometry. Roller perches if you can afford them, and solid mount adjustable front struts. Get good Bilstein shocks, and maybe some 600-620# variable-rate springs (harder to tune for track use, but they work great on the street!). Use a 1" front sway bar. Do a modern alignment with more caster. 3.5 degrees for manual, and 5 or more for power steering. More caster will increase return-to-center, improve feel, and add high-speed stability. It will also make your wheel a bit harder to turn. The rest of the original settings work well with modern tires; 0- .5 degrees of camber, and 1/16" of toe in on each side so the tires are parallel when you're going down the road.

Welcome to AFM, Moxx!

Wow! Thanks for all the info! I’ll write down the specs on alignment so I have them ready when we get this Mustang on the road.
I’ve got a sway bar kit picked out. It’s a 1”, so I’ll lock that one in on my budget.
What do you mean when you say “Do a Shelby drop”? I’m not planning to drop it, in fact I was considering going with bigger tires, which may require a slight lift. I’ll let you know when I pick out tires and wheels (I hadn’t gotten that far, so I just put $1200 in my budget spreadsheet for tires and wheels.) I’m not gonna do any racing, so I just want it to be a comfortable ride, and to not lose traction on corners or have a ton of body roll.
Thanks again for the advice. I really appreciate it!

 

[Grimbrand]

The "Shelby (Arning) drop" is a method for correcting your front end geometry.

In the 60s, insurance companies began cracking down on hot rodding, and didn't want teens driving dangerously in all the high-powered cars on the streets. One way the manufacturers tried to create 'safety' was ensuring that their cars would understeer.

Oversteer is fun. You go into a corner too fast, hang the tail out, rear tires howling, and it's a hoot, right?

But understeer? In a situation where you're going too fast into a corner, the car tends to plow straight ahead and doesn't make the turn. It's not fun, and after one scary skid into a ditch, most kids learned to drive more sedately.

In a Mustang or Cougar, (in fact most Fords of this era) have the upper control arm at a fairly steep angle compared to the lower control arm. When the suspension compresses, the top of the tire swings out, the bottom rolls in, and the outside tire in a turn rolls over onto its sidewall, or at least lifts most of its inner tread off the ground. Instant understeer.

Carrol Shelby, when asked to make the "Secretary's car" (Mustang) into something meaner, decided with Klaus Arning to fix this very simply. He moved the upper control arm down by drilling new bolt holes. The upper control arm, now more parallel the lower one, helps keep the tread firmly planted on the ground, possibly even gaining just a little camber in a turn to brace against it.

It does lower the nose about 5/8" to 3/4", typically, but it's not nearly as much about stance as it is about improving handling, and reducing body roll as well. Combined with a stiffer-than-stock front swaybar and a few other minor bits, the factory suspension on these cars lets them handle very well indeed. Instead of wallowing around corners, leaning over like a yacht with the tires howling, it will just do what it's supposed to. Best of all, the Shelby drop is essentially free!

Aftermarket upper control arms are available with roller spring perches that really free up the front suspension, and many of them come with built-in geometry that allows you to use the original holes in your shock tower, instead of drilling new ones with a template. StreetOrTrack is a great place to look for a set, if you're interested.

 

[Beechkid]

. And when you say 50 series tires, are you talking about the model, right? Not the second number in a tire profile, the one that indicates % of its width in height from the rim.

yes, referring to tire profile...... the one that indicates % of its width in height from the rim... that also determines the "stiffness" of the tire sidewall...... when you go shorter than 50 series, the tire sidewalls have very little flex/give to them...... hit a bump, the tire will jump!

 

[Grimbrand]

For a track-oriented car, running really big rims with 50, 40, even 30 series rubber bands can pay some dividends because the sidewalls can't flex or deflect as much. But this also presumes that the track is nice and smooth, the wheels are light and strong, and the suspension is really good at keeping the tread flat on the road. Deficiencies in the suspension or road result in either bad handling or wheel damage if your sidewalls are too short.

For street driven cars, a set of 60 series tires on 15" rims can soak up a lot of imperfections in the road, delivering a very good ride - and still allowing good handling. Tires with taller sidewalls deflect more when cornering, but it doesn't feel odd when you're driving with them. They tend to be more forgiving, and stay planted well in most conditions.

It's all a tradeoff. Razor sharp handling, unforgiving manners when pushed to the limits, and excellent road feel (along with every tiny crack and pebble), or a more relaxed cruiser with smooth ride that tends to offer more warning when pushed beyond reasonable bounds.

It comes down to personal preference, as well as where it's going to be driven!

 

[paul289]

I will say that having a good rear suspension really does wonders! I've got a Griggs torque arm system, and it handles way better than leaf springs could ever hope to! Granted, it does cost a fair bit. But you can always add a Panhard bar or Watts link to tighten up the rear handling, and you can also add a torque arm to help put power down and get rid of wheel hop. Otherwise, get the best shocks that you can afford. Tires and shocks are the best things you can do for handling, really.

 

[Grimbrand]

I will say that having a good rear suspension really does wonders! I've got a Griggs torque arm system, and it handles way better than leaf springs could ever hope to! Granted, it does cost a fair bit. But you can always add a Panhard bar or Watts link to tighten up the rear handling, and you can also add a torque arm to help put power down and get rid of wheel hop. Otherwise, get the best shocks that you can afford. Tires and shocks are the best things you can do for handling, really.

Just in case you don't know him - Paul would definitely know, folks. He drives his car the way you wish you could.