1973 duster wheel bolt pattern

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Penstarpurist

Penstarpurist

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So we are installing the 8.75 rearend we got out of a '71 340 4 spd duster and putting it in our 73 duster big block project. My baffling moment is this. The 71 rearend is a 4"sbp, no suprise. I had assumed the 7.25 out of the slant six 73 duster would be a big bolt pattern. Out of curiosity, I measured the bolt patterns from both rearends and they were both sbp. They were both 4" bolt pattern. Am I wrong in thinking the 73 was a big bolt pattern, or did they just use up what they had on hand that year before going to the big bolt pattern on cars built that year? The fronts are 4 1/2" big bolt disc. What the heck is going on? I guess someone could have trashed the old 7.25 and swapped in an older 7.25, though with as beaten as this car was when we got it I don't think anyone would have fixed it if it failed. They would have left it for dead. Any thoughts?
 
Hey man, i got a 73 duster slant 6, it came with sbp 71/4. Got a 83/4 bbp now though :D
 
I should have looked for a bbp 8.75 to match the fronts. But when I found a sure grip Richmond 4.11 complete for $750 I jumped on it. Just figured I'd put bbp rallye wheels on the front and sbp rallye wheels on the back. Easy enough to remedy. And I guess it's not important what size the rear pattern was, as I'm putting in another sbp anyways. But just thought it odd and wanted to see what you guys think.
 
But at least it sounds like a somewhat common thing for 73 then. Huh. Learn something new everyday. Thanks for letting me know deathdust73 about yours.
 
Penstarpurist said:
I should have looked for a bbp 8.75 to match the fronts. But when I found a sure grip Richmond 4.11 complete for $750 I jumped on it. Just figured I'd put bbp rallye wheels on the front and sbp rallye wheels on the back. Easy enough to remedy. And I guess it's not important what size the rear pattern was, as I'm putting in another sbp anyways. But just thought it odd and wanted to see what you guys think.
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Oh no, i spent a great amount on my rear, started with a real a body 83/4 housing from fabo for 300$, bbp axles 150, new studs lines breaks ?$ but the real kicker was i had a shop swap my gears and my center section for some old pos parts and that fiasco had me 600+ thrown in the trash, rear didnt work, tried getting it fixd at another shop due to them telling me they didnt swap parts and to kick rocks, rear still broken, after trying to fix the clutch pack 80$ for kit, so ended up dropping another 6 on a damn tru trac.. least i know shes solid, the slant cant even burn out on wet ground with that thing lol but yea itll look wierd to see the bolts closer together in the back wheels but nothing crazy. Id leave it, cus than you need axles brakes etc and since its all out you might as well get green bearing and ehhh save the bucks and keep it its still a 83/4 :)
 
Penstarpurist said:
But at least it sounds like a somewhat common thing for 73 then. Huh. Learn something new everyday. Thanks for letting me know deathdust73 about yours.
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Yup no problem! Wanna know something funny too? I wrecked drifting my s6 duster on this intersection right? Well i bought a whole parts car 73 scamp for 350 thinking i bent my k member so i swapped k's and put all new bushing since everything was out well, moral is, my original duster brakes were 9 in sb the scamp were 10in sb. I had no idea until i bought wrong brake shoes n measured. Same yr different equipment, still dont know why I haven't just gotten a chevy with all the crap this car has put me through haha mopars wierd af!
 
We pulled the rearend down to an empty case, put the green bearings in it, new brakes, wheel cylinders, seals, etc. So it's been completely rebuilt. I should've grabbed up a set of bbp axles while it was taken down in pieces. And if I run across a set I'll grab them up and swap them out at some point. But until then, I'm running the ones I got. Sorry to hear about your experience getting yours up to speed, but like you said, ay least now you know what you got is solid.
 
The '73 cars with 4 wheel drum brakes had the small bolt pattern. '73 cars with disks in the front from the factory were BBP front and rear. If your '73 had both it was either a 4 wheel drum car that someone upgraded to disks, or a BBP disk car that someone took the BBP rear out of.

Probably the first one, because even the 4 wheel drum cars had the larger ball joint UCA's. So the disk swap just requires the disk spindles and brake parts.
 
Penstarpurist said:
We pulled the rearend down to an empty case, put the green bearings in it, new brakes, wheel cylinders, seals, etc. So it's been completely rebuilt. I should've grabbed up a set of bbp axles while it was taken down in pieces. And if I run across a set I'll grab them up and swap them out at some point. But until then, I'm running the ones I got. Sorry to hear about your experience getting yours up to speed, but like you said, ay least now you know what you got is solid.
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Definitely, got a 383 30 over closed chamber head engine and a rev mvb 727 mating up to that 83/4 and she'll still take more!
 
72bluNblu said:
The '73 cars with 4 wheel drum brakes had the small bolt pattern. '73 cars with disks in the front from the factory were BBP front and rear. If your '73 had both it was either a 4 wheel drum car that someone upgraded to disks, or a BBP disk car that someone took the BBP rear out of.

Probably the first one, because even the 4 wheel drum cars had the larger ball joint UCA's. So the disk swap just requires the disk spindles and brake parts.
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I have no idea where i got confused, but my scamp 10in sb brakes are drum i have to convert to disk to get bbp wheels in the front, dont HAVE to but might as well haha
 
I have to remind myself that the car is 40+ years old and I'm sure had a few owners to say the least. So if there is no way it would have rolled out of the factory with mixed bolt patterns, then someone at sometime swapped in either a different rearend or disc brake fronts. I'm leaning towards it being the rearend swapped, as the amount of abuse and damage to this thing to me would suggest that no one would have done upgrades to a /6 they mistreated. I could see someone rolling in a used rearend after they grenaded the other one to keep the dukes of hazard lifestyle they obviously had for it.
 
Honestly, i would have gotten a '68 - '70 B body 8 3/4 rear and just moved the spring perches in 1'' on both sides.
I did this with my '74 Dart Sport and am very happy with the results.
With this swap, it is a lot cheaper than getting an A body rear housing and then buying axles etc.
And you get big bolt pattern automatically with this set up..........what's not to like?
As far as wheels, i have factory 15X6 1/2'' rallye wheels and 255 60 15s on my car and with the right offset wheel, i could easily fit 275s in there. I did roll the inner wheel lips in just to be sure and it looks and works great.
The Duster/Dart Sport wheel openings and quarters are the same, and you can fit a pretty good sized tire in there without mini tubbing or moving the springs inboard.
I personally think that the stock width A body rears on these cars with stock wheels looks too narrow, and the B body rear gives the car a better look as well as a wider track.

As for the '73 and up cars brakes, all slant six cars with standard non power brakes were small bolt pattern front and rear.
All cars with power brakes or a v8 got big bolt pattern front and rear with front discs.
All of the '73 and newer sbp slant 6 cars that I've seen had 10'' front brakes with a finned drum.
Also, all cars built after December 31st 1975 had big bolt pattern and front discs regardless of power or standard brakes or engine ordered.

This info has come from many years of personal research and looking at literally hundreds of cars and parting out several as well..........
I hope this helps,
Tom.
 
also the '65 b body 8 3/4 is slightly narrower than its cousin the 66-70 b body 8 3/4.. bolts right in no perch moving. might have to jiggle it 3/4 inch..... the 71 up is too wide for the A body.
 
Shoot, my car is non power manual brakes, manual non power steering with front 10" disc brakes. My last 73 duster (exact same color, just coincidence) was also non power brakes, manual steering and still had 10" front disc brakes drum big bolt rear. The only difference being this one now is mixed bolt patterns. So from my experience they did build manual non power front disc brakes in bbp. As for the b-body rearend, I did consider it initially. In doing research and talking with a few guys who have used them they all said they wished they would have gone with the correct A-body rearend as ever time they put a full tank of gas in there the car would rub tires on the fender lips, especially with any passengers in the back seat. I do agree the tires look too small on A-bodies with a stock rearend.
 
Penstarpurist said:
Shoot, my car is non power manual brakes, manual non power steering with front 10" disc brakes. My last 73 duster (exact same color, just coincidence) was also non power brakes, manual steering and still had 10" front disc brakes drum big bolt rear. The only difference being this one now is mixed bolt patterns. So from my experience they did build manual non power front disc brakes in bbp. As for the b-body rearend, I did consider it initially. In doing research and talking with a few guys who have used them they all said they wished they would have gone with the correct A-body rearend as ever time they put a full tank of gas in there the car would rub tires on the fender lips, especially with any passengers in the back seat. I do agree the tires look too small on A-bodies with a stock rearend.
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This is one of the reasons i bent my inner wheel lips in, it was easy and they stick in from the quarter an inch or so with some sharp edges to boot.
If your springs are worn out or you want your car low, maybe going the A body width is for you.
I also used Super Stock springs on my car, and when i fill it up with gas, the rear end doesn't drop at all.
It's all in what you want to achieve i guess.

For sure, the mixed bolt patterns from front and rear are wrong, someone changed something sometime in the car's life.

Is your car (and the other one that you mentioned) a factory slant 6 car?
I have seen plenty of standard brake v8 cars with bbp discs and bbp 7 1/4 rears, heck i even have a couple of them right now..........
 
Both were factory /6 cars both by k member and vin tag. I removed the /6 out of this one, and my last one someone had put in a v8 on the /6 k member by bolting in one side and using a chain from the block to the inner fender well. Everytime you accelerated it would lift the engine into the hood and dent it. I pulled the k member out and put in a small block v8 k member in out of a wrecked v8 dart sport I had, as well as the 8.75 from it. The last guy that had owned it did the half *** swap in of the v8. He told me he had pulled the /6 out and did the swap. If you want to call it that.
 
I got a 73 4 door valiant with a 318 power steering ac and power brakes what bolt pattern would have come on mine I’m not around it right now to check and I was wanting to order some wheels so that next time I’m around I can throw em on, thanks for the help
 
73valiantfourdoor said:
I got a 73 4 door valiant with a 318 power steering ac and power brakes what bolt pattern would have come on mine I’m not around it right now to check and I was wanting to order some wheels so that next time I’m around I can throw em on, thanks for the help
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same as above. if it's drums, it'll be SBP if it's discs BBP.

but also, as above, anything can change in 50 years. verify before you buy or at least make sure you can return them if they're wrong.
 
If it’s a ‘73 and the 318 is original it should have disk brakes in the front and be 5x4.5”.

All the V8 cars got disks starting in ‘73, and that meant they were also BBP. But yeah, verify that because a lot can change in 50 years.

The /6 cars in ‘73 (and beyond) could still be drum/drum, and they stayed SBP. That carried all the way to mid year ‘76 when front disks were mandated.
 
72bluNblu said:
If it’s a ‘73 and the 318 is original it should have disk brakes in the front and be 5x4.5”.

All the V8 cars got disks starting in ‘73, and that meant they were also BBP. But yeah, verify that because a lot can change in 50 years.

The /6 cars in ‘73 (and beyond) could still be drum/drum, and they stayed SBP. That carried all the way to mid year ‘76 when front disks were mandated.
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I argued this numerous times against some dorks at another forum....they claimed because their parts books for 1976 didn't show front drum brakes on the A bodies that they never existed.
I've owned them. I drove them yet these brainiacs thought they were the authority on the matter.
 
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