Disc Brake Dilemma, need advice

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octanejunkie

octanejunkie

Mopar Padawan
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I bought a 71 Scamp that had a front disc brake conversion already done, problem is the car is now BBP front and SBP rear, plus the MC was NOT replaced according to the seller so I got a problem

Besides upgrading to a Disc/Drum MC like the Raybestos MC36426, I am considering either upgrading my rear end to BBP or downgrading my front hubs to SBP - seems smarter to go BBP but it would be at greater expense since I have 2 rear ends to work with - a 7.25 on the car and a spare 8.75 A-body rear - not sure which I want to run yet...

Option 1. Going SBP up front
I believe the disc brake swap was the 73 Dart route complete with new upper arms - is it possible to swap to SBP hubs keeping all other 73 hardware or would I need to replace more parts?

Option 2. Going BBP in the rear
Not sure it is worth upgrading to BBP axles on the 7.25 rear, but if I build the 8.75 it seems a no-brainer since I have an SG center section. The issue with the 8.75 build is gearing, I have 2.76 and 3.90 gear sets but want 2.94s - cannot find them anywhere new, I guess the 2.76s will do for the street

Please advise me if I'm looking in the wrong direction here
 
Build the 8 3/4 rear,with big bolt axles.

2.76 is a great highway gear.

3.23 & 3.55 gears are great all-around gears,and plentiful. Maybe even use the 3.90 gear for the street.

What is your set-up ? Car/engine/trans etc.......
What do you want to do with the car ?
 
octanejunkie said:
I bought a 71 Scamp that had a front disc brake conversion already done, problem is the car is now BBP front and SBP rear, plus the MC was NOT replaced according to the seller so I got a problem

Besides upgrading to a Disc/Drum MC like the Raybestos MC36426, I am considering either upgrading my rear end to BBP or downgrading my front hubs to SBP - seems smarter to go BBP but it would be at greater expense since I have 2 rear ends to work with - a 7.25 on the car and a spare 8.75 A-body rear - not sure which I want to run yet...

Option 1. Going SBP up front
I believe the disc brake swap was the 73 Dart route complete with new upper arms - is it possible to swap to SBP hubs keeping all other 73 hardware or would I need to replace more parts?

Option 2. Going BBP in the rear
Not sure it is worth upgrading to BBP axles on the 7.25 rear, but if I build the 8.75 it seems a no-brainer since I have an SG center section. The issue with the 8.75 build is gearing, I have 2.76 and 3.90 gear sets but want 2.94s - cannot find them anywhere new, I guess the 2.76s will do for the street

Please advise me if I'm looking in the wrong direction here
Click to expand...

I'd complete the BBP rear. Do you have a complete drum to drum A-body rear end.

You could just redrill the axles and drums for under $150. You then use grade 8 cap screws in the new threaded large pattern hole in your old small pattern axles. I've run this in my Barracuda for 50K miles and 16 years. Down fall of that setup is that you use more expensive rear drums. And when you put on new ones you have to have those redrilled. Sutton Engineering in City of Industry will do that for you. He's a Mopar guy.

If you buy new axles you'll have to get new bearing too for them, and you have to get 10" backing plates off a junk car. Any 8 3/4 large bolt 10" Drum backing plate will do. Then you need brakes, hardware, drums (cheaper than the SBP drums).

The front 4 piston disk swap will cost your $300 for used rotors, calipers, and upper arms. And that stuff is all used. It's sounds like you have a complete functioning front BBP disk setup, except for suspect master cylinder.

Do you have manual or power brakes. If you go manual the 73 disk swap, look for a 15/16 or 1" bore master cylinder.
 
oldkimmer said:
......I can help u out with a used set.................kim........
Click to expand...
Cool, used set of what? SBP hubs? Wondering if they will fit my current BBP setup up front... I am more inclined to spend the $$ for BBP axles, $250 total... Hmmmm

Johnny Dart said:
Build the 8 3/4 rear,with big bolt axles.

2.76 is a great highway gear.

3.23 & 3.55 gears are great all-around gears,and plentiful. Maybe even use the 3.90 gear for the street.

What is your set-up ? Car/engine/trans etc.......
What do you want to do with the car ?
Click to expand...

I am so torn here, I really want 3.23s or 3.55s like you say, but with a 904 trans 3.90 for the street seems unreasonable...

Car currently has an old 318 in it, the trans was "built" to withstand the abuse of a 360 magnum the seller was going to install, I have that motor in parts ready to assemble

The best question yet I cannot answer, what do I want to do with the car? I think I'll drive if a while, see how I feel about restoring it, and if I don't feel like another project, I'll build a race car out of it, which is when the 3.90 gears start looking good... Overall I was thinking 2.94s might be a nice compromise but will not win any races. If I had an OD trans I'd run the 3.90s in a heartbeat!

autoxcuda said:
I'd complete the BBP rear. Do you have a complete drum to drum A-body rear end.

You could just redrill the axles and drums for under $150. You then use grade 8 cap screws in the new threaded large pattern hole in your old small pattern axles. I've run this in my Barracuda for 50K miles and 16 years. Down fall of that setup is that you use more expensive rear drums. And when you put on new ones you have to have those redrilled. Sutton Engineering in City of Industry will do that for you. He's a Mopar guy.

If you buy new axles you'll have to get new bearing too for them, and you have to get 10" backing plates off a junk car. Any 8 3/4 large bolt 10" Drum backing plate will do. Then you need brakes, hardware, drums (cheaper than the SBP drums).

The front 4 piston disk swap will cost your $300 for used rotors, calipers, and upper arms. And that stuff is all used. It's sounds like you have a complete functioning front BBP disk setup, except for suspect master cylinder.

Do you have manual or power brakes. If you go manual the 73 disk swap, look for a 15/16 or 1" bore master cylinder.
Click to expand...

My axles cannot be re-drilled, too many holes in them already according to Anthony at Hoopers in Sun Valley, they have done 3 rear ends for me flawlessly so I trust them. New axles are $125 each for new BBPs, not a huge expense there, but then new bearings add about another $200 overall... and NO I don't have backplates, yet another expense. All in all, building the 8-3/4 rear is looking like a $1000+ adventure and I'm not even sure what I want to do with the car yet

Obviously I could run my current setup and would only need BBP axles for the 7.25 until I figure out what I want to do with the car - BTW it is running and drivable, none of these expenses are REALLY necessary... Not sure what 7.25 gear ratios are available out there, didn't find too many so far

Honestly I haven't even pulled the wheels off to look yet, not sure what is up front for brake hardware... I am hoping the MC swap will be as simple as just the MC, no metering block, no residual or proportioning valves, no extra bullsh*t, but it usually doesn't work out that way it seems
 
sbp wheels are expensive and hard to find

bbp wheels are a dime a dozen and have a huge selection of wheels

from what i understand the 73 and up are better brakes than the sbp ones and you have a bigger nuckle




hope that helps
or for the time being just get some steelies paint them black get crome lugnuts and a raised white letter tire
 
autoxcuda said:
You could just redrill the axles and drums for under $150. You then use grade 8 cap screws in the new threaded large pattern hole in your old small pattern axles. I've run this in my Barracuda for 50K miles and 16 years. Down fall of that setup is that you use more expensive rear drums. And when you put on new ones you have to have those redrilled. Sutton Engineering in City of Industry will do that for you. He's a Mopar guy.

If you buy new axles you'll have to get new bearing too for them, and you have to get 10" backing plates off a junk car. Any 8 3/4 large bolt 10" Drum backing plate will do. Then you need brakes, hardware, drums (cheaper than the SBP drums).
Click to expand...


Good information here ^^^ Question though... If he got his old SBP drums redrilled can he just put them on the car and be done? He could just rebuild them if he has them redrilld to LBP and put them back on the car verses going out and looking for a donor car with LBP correct? I ask b/c this is what I plan on doing very soon.
 
FYI, any car or truck with 10" or 11" LBP drums on an 8.25 or 8.75 rear end will work. I have seen many at junkyards around here.
 
USCG CHARGER said:
Good information here ^^^ Question though... If he got his old SBP drums redrilled can he just put them on the car and be done? He could just rebuild them if he has them redrilld to LBP and put them back on the car verses going out and looking for a donor car with LBP correct? I ask b/c this is what I plan on doing very soon.
Click to expand...

When you have your old SBP axles redrilled to LBP they redrill your SBP drums at the same time.

You will not be able to buy new LBP drums and use them when you do this swap. This is because the redrilled SBP axles still have the smaller SBP center register that centers the SBP type drums/axles (I know I should have mentioned that in the first deal). Also any LBP rims will not be center registered. Not a end of the world deal as all Magnum 500's and almost all aftermarket aluminum rims are not center registered.

Also SBP drums run 1.75 wide shoes, whereas the other common 10" Mopar drums run 2" shoes.

The key to doing this is running capscrews/bolts as wheel studs. and having the new axle holes threaded. If you try to redrill the bolt pattern and use regular press in lugs, the extra diameter of the lug shoulder runs into the access hole on the axle flange (see picture) and it won't work.

I have a feeling Anthony at Hoopers is thinking about installing lugs, so that way won't work. Or he doesn't do the particular mod often and doesn't feel comfortable with it.

I had my axles and drums redrilled by Mazzolini in 1994 for $90. Then I had to by 20 grade 8 bolts and torque them down with loctite. Mazzolini he just sends his stuff to Sutton Engineering. He had pictures of small block drag race cars on small slicks that he said ran this setup.

See the head of the capsrew on the back of the axle flange in the first picture?

Copy of RRAAxleSeal8_21_09Lg10.JPG


Copy of RRAAxleSeal8_21_09Md08.JPG
 
autoxcuda said:
When you have your old SBP axles redrilled to LBP they redrill your SBP drums at the same time.

You will not be able to buy new LBP drums and use them when you do this swap. This is because the redrilled SBP axles still have the smaller SBP center register that centers the SBP type drums/axles (I know I should have mentioned that in the first deal). Also any LBP rims will not be center registered. Not a end of the world deal as all Magnum 500's and almost all aftermarket aluminum rims are not center registered.

Also SBP drums run 1.75 wide shoes, whereas the other common 10" Mopar drums run 2" shoes.

The key to doing this is running capscrews/bolts as wheel studs. and having the new axle holes threaded. If you try to redrill the bolt pattern and use regular press in lugs, the extra diameter of the lug shoulder runs into the access hole on the axle flange (see picture) and it won't work.

I have a feeling Anthony at Hoopers is thinking about installing lugs, so that way won't work. Or he doesn't do the particular mod often and doesn't feel comfortable with it.

I had my axles and drums redrilled by Mazzolini in 1994 for $90. Then I had to by 20 grade 8 bolts and torque them down with loctite. Mazzolini he just sends his stuff to Sutton Engineering. He had pictures of small block drag race cars on small slicks that he said ran this setup.

See the head of the capsrew on the back of the axle flange in the first picture?
Click to expand...

Hmm, very good info indeed, obviously there is experience talking here\

Mazzolini lists 8-3/4 axles for $60 each, if they are BBP that is the way to go IMO, but thanks for the info on re-drilling. Personally I'd rather sell my SBP axles or keep them for a rainy day and go with something "factory" and aftermarket friendly - but that's just me...

redfastback said:
FYI, any car or truck with 10" or 11" LBP drums on an 8.25 or 8.75 rear end will work. I have seen many at junkyards around here.
Click to expand...

Thanks for the info, I see another trip to the junkyard in my near future!
 
Johnny Dart said:
Build the 8 3/4 rear,with big bolt axles.

2.76 is a great highway gear.

3.23 & 3.55 gears are great all-around gears,and plentiful. Maybe even use the 3.90 gear for the street.

What is your set-up ? Car/engine/trans etc.......
What do you want to do with the car ?
Click to expand...

I like this plan. If your budget doesnt allow for new axles,just redrill the old ones with the bb pattern.
 
needsaresto said:
I like this plan. If your budget doesnt allow for new axles,just redrill the old ones with the bb pattern.
Click to expand...

I like this plan too

Until I decide what how to build my 8.75 rear I might just throw an SG carrier with 2.93 gears into my 7-1/4 rear end - I have money to burn apparently - or I just really like positraction and almost-3 series gears

Thanks for all the advice Johnny Dart, you're a good egg
 
If yor just going to drive it around until you decide to rebuild or not you could
use wheel adapters to go from 5x4" to 5x4.5". then you can use the BBP and then you only need one spare tire instead of one for the BBP and one for the SBP.
I know they are frowned upon by some. For street they should be fine.
JEGS has them for about $60.00.

Just a thought.
 
norshorblufish said:
If yor just going to drive it around until you decide to rebuild or not you could
use wheel adapters to go from 5x4" to 5x4.5". then you can use the BBP and then you only need one spare tire instead of one for the BBP and one for the SBP.
I know they are frowned upon by some. For street they should be fine.
JEGS has them for about $60.00.

Just a thought.
Click to expand...

I got them on the car now...
 
Don't forget to check any 7-1/4 a body rear ends you may see: Mine from a '73 disc brake Duster is BBP from the factory. Just my 2 cents worth.

Later,
Bruce B.
 
I would save the money and go all big bolt it it were me. Like stated already. The cheapest way may be to find a 74-up 7 1/4 rear. I would rather go 8 3/4 though
 
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