Upgrade for '70 Swinger 340 rear

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70dart340

70dart340

FABO Gold Member
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Many thanks to all over the years(!) for the help on my '70 Swinger 340. My 408 is in the end stages of construction, I have a Pat Blais built 727 with a freshly built FTI 3600 stall speed hard hit converter. Time now for the rear end. The stock open 3.23 8 3/4 will ned help for the mostly street driven 500+HP small block. I also have a complete 8 3/4 with a 3.23 SG I picked up years ago. I'm thinking of rebuilding the spare rear with a 3.55 SG and new SS springs. Maybe Caltracs? Looking for advice from my FABO family for the most important part of the traction puzzle. My hide is as thick as an old Santa Gertruda, so let your opinions fly! It's been quiet around here lately, so I thought I'd kick that hornets' nest! Ford 8.8? Dr. Diff? I'd like to utilize what I've collected over the years, but I want a badass, stock looking 1970 Swinger 340. Thanks to all in advance.
 
What rear tire and wheel, that's the first part of "traction"
 
70dart340 said:
Many thanks to all over the years(!) for the help on my '70 Swinger 340. My 408 is in the end stages of construction, I have a Pat Blais built 727 with a freshly built FTI 3600 stall speed hard hit converter. Time now for the rear end. The stock open 3.23 8 3/4 will ned help for the mostly street driven 500+HP small block. I also have a complete 8 3/4 with a 3.23 SG I picked up years ago. I'm thinking of rebuilding the spare rear with a 3.55 SG and new SS springs. Maybe Caltracs? Looking for advice from my FABO family for the most important part of the traction puzzle. My hide is as thick as an old Santa Gertruda, so let your opinions fly! It's been quiet around here lately, so I thought I'd kick that hornets' nest! Ford 8.8? Dr. Diff? I'd like to utilize what I've collected over the years, but I want a badass, stock looking 1970 Swinger 340. Thanks to all in advance.
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Street car, 500 horse, you could get by with a 7 1/4. Just kidding. That combination won't get enough traction on the street to hurt a 8 3/4. You will be spending all your time burning tires and trying to keep the back end behind you regardless of SS springs or Cal Tracks.
 
The ''mostly street'' and ''stock looking'' is the hard part. The rear springs and caltrac type bars would be a nice addition. If your street driving is just local, you could tackle it with small T-bars and some adjustable shocks although it will be a little different handling wise. The bars kinda give away the ''stock look'' though. Back in my day...lol, the biggest bias tire you could fit and some 70/30 rear shocks would hook pretty well, especially on concrete streets, up to about 425hp, but most of these stroker engines are a lot stronger now days.
 
first and foremost the SS springs are gonna put the *** of the car way up in the air. if you're fine with that look, then carry on. but also remember that SS springs are designed as drag race springs and feature more leafs on the one side so the car may sit funny and it will ride terribly on the street.

one of the key components to traction is tire size. so, what are you working with there?

i think a 3.55 is perfectly acceptable street gear. with a "street tire" i don't think you'll get enough bite to hurt a well built 8.75.

personally, i'd build out that 3.55 set, install some HD springs and roll. if you're feeling frisky, cal tracs are always an option. or you could sell all the 8.75 stuff and have dr. diff build out a dana and probably come out even.
 
70dart340 said:
Many thanks to all over the years(!) for the help on my '70 Swinger 340. My 408 is in the end stages of construction, I have a Pat Blais built 727 with a freshly built FTI 3600 stall speed hard hit converter. Time now for the rear end. The stock open 3.23 8 3/4 will ned help for the mostly street driven 500+HP small block. I also have a complete 8 3/4 with a 3.23 SG I picked up years ago. I'm thinking of rebuilding the spare rear with a 3.55 SG and new SS springs. Maybe Caltracs? Looking for advice from my FABO family for the most important part of the traction puzzle. My hide is as thick as an old Santa Gertruda, so let your opinions fly! It's been quiet around here lately, so I thought I'd kick that hornets' nest! Ford 8.8? Dr. Diff? I'd like to utilize what I've collected over the years, but I want a badass, stock looking 1970 Swinger 340. Thanks to all in advance.
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Hey Paul. SS springs with rubber bushings ride the best and a lowering block can be used to drop the rear if you desire. I can personally swing by and show you what a two inch drop block does on my Magnum.

I have Caltracs on the wife’s car. So I can return the next day and have you drive it. The mono springs by themselves are OK and fine but adding the tracking bars under them downgrades the ride a shade or two, depending on how you like your stuff.

On my ‘71 Duster, I have SS springs & the stink bug look is t really big or massively present. Tires are part of the key and that’s front and rear. Also the fronts ride height has a play in the rake the car will have.

I’d drive the Duster over but I need to work on it before anything happens.
 
My thanks to all. I currently have a set of 215/70R14s for shop tires. I can't find any 14" performance tires. I'm thinking of getting a set of 4" SBP 15" ralleys from summit. Maybe some 215/70 15S? I think 3.55's will do well for the street, and occasional trip to Rob's. Should I upgrade the yokes on my 741, or are they enough? A little rake is ok. Thanks for the kind offer, Rob, but I think it's my turn to run down the I-95 to your house. I'll PM you with pictures of what I have so far.

20230724_110547 (1).jpg


Swinger rear on dollies.jpg
 
Greenbearings, or tapered? so many questions. I want to get this old Girl on the road! One more dessicant filter, and my paint and body booth will be open. More questions for the family.....
 
This is just what I would do.....
I'd keep the 3.23 suregrip intact, and redo the 3.23 open with 3.91s and a clutch suregrip from Dr Diff. And get some good axles with big bolt pattern from him, while I was at it.
Agree with above, ss springs and good shocks should be plenty, even with drag radials, and lowering blocks if you want. I have ss springs on my car, and it sits just fine for me, not even remotely stinkbug. But then, I got the 3400lb springs for my 3400 lb car.
 
Last I looked, there are a total of two performance 14" tires in the summit catalog. The switch to a 15" wheel is a no-brainer, imo.

But, for what it's worth.....
M&H shows a 235/60x14 muscle car drag tire (their name) bias wrinkle wall treaded dot tire, and....
Hoosier quick time pro, 26x9.5-14LT, really full bias slicks, with a few grooves
and a dot (the LT light truck part of the designation)
The Hoosier has even less tread than the M&H.
Do yourself a favor, get you some 15s.
 
My $0.02...

My avatar has a 408 like you are talking about. I use a 489 case 8-3/4 with a spooled 4.10 gear and Moser 35-spline axles. 8" ATI converter that stalls right at 5000 rpm. Split mono Caltracs with Calvert 9-way rear shocks. 28x10.5W bias slicks at the track. RMVB CRT 727. Unless there is water or something stupid wrong with the track, traction is not something I have to think about. The car just leaves.

On the street, tires are M/T ET Streets P295/55R15's. Traction on the street is "ok" but honestly, I don't often test it as these 408's make so much torque and street surfaces are so variable....it just ain't worth it! Plus I tend to be a bit cautious due to the spool as well.

Caltracs on the street? Mine are set pretty tight so they do make some noise on shifts but in a car like this, who cares?? It's part of the fun of the car. If I wanted an easy to drive car that ran low 11's, I'd get one of the new cars - many of them can do that. I just prefer these old heaps!!

IMG_1735(1).jpg
 
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Thanks, new neighbor! I'll PM you with more questions, if you don't mind. When you head to Bithlo, I have your overnight pit stop. Room for you and your better half, and your trailer with your beasts. Paul.
 
Time to hit the hay. Thanks to all for the great information. FABO comes through again! I'll PM several members tomorrow after my pacemaker appointment early afternoon. I'll post some photos of my spare 3.23 SG so members can positively ID what type of SG I have in my spare punkin. I'll send a PM to our favorite mod, TMM, about filter questions for my paint booth. I'll also post questions about dropping my fuel tank and rear suspension for cleaning and repair/rebuild. I love retirement and my garage! Keep 'em coming, Brothers. Nothing from Georgia yet, RRR. I'm waiting.
 
Get rid of that V8 junk and put a real upgrade in it. Slant 6 baby!
 
70dart340 said:
Thanks, new neighbor! I'll PM you with more questions, if you don't mind. When you head to Bithlo, I have your overnight pit stop. Room for you and your better half, and your trailer with your beasts. Paul.
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Very kind of you - we'll definitely hook up!!
 
how much do you want to spend, what bolt pattern do you want to use, and what type of gearing do you want? if you want the large bolt patter, on a budget, your best bet is to get an explorer 8.8. Older ones use 10x2.5" drums, newer ones disc. Around here you can find 3.73/Limited Slips in yards everywhere for less than $200, grab a 2nd short axle out of another one, shorten one side of the housing to center the pumpkin (using the 2nd short axle shaft on that side), cut off extraneous bracketry, and weld on spring perches. That gets you a rear about 56.5" wide that will handle a ton of HP for not a lot of coin.
 
Super Stock springs are designed for the drag strip. They are an attempt to get the car to launch flat so when the car is just sitting or driving down the road one side in the back is higher than the other. You can get A-body 6 leaf springs from ESPO that will work a lot better for driving around (you said street car, right?). Do you (or do you want to) drive the car out on the highway at all. Sustained driving over 50 mph with 3.91 gears is torture to me. IMHO 3.55 is as low as I would go. If it's really a street car, tapered bearing all the way.
 
str12-340 said:
Super Stock springs are designed for the drag strip. They are an attempt to get the car to launch flat so when the car is just sitting or driving down the road one side in the back is higher than the other. You can get A-body 6 leaf springs from ESPO that will work a lot better for driving around (you said street car, right?). Do you (or do you want to) drive the car out on the highway at all. Sustained driving over 50 mph with 3.91 gears is torture to me. IMHO 3.55 is as low as I would go. If it's really a street car, tapered bearing all the way.
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I do not notice a lean. Yes, a 3.23, 489 rear.
 
I have used the ESPO 6 leaf springs. 1 Inch I over bend. It gives it a nice rake, not to high at all. Thumbs up to them here.
 
I'll look at the ESPO springs tonight. Many thanks to all for their help, especially RRR.
 
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