Power brake conversion questions ('70 Dart Swinger)

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zackw

zackw

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Hey all, I recently bought a 1970 Dart that I'm planning to make my daily driver. I'm thinking it would be worthwhile to upgrade the brakes. It's a 225 6cyl auto. Is it a good idea to buy a booster/master cylinder kit from Ebay? How close are these kits to stock? I want to be able to get replacement parts from Autozone etc if necessary.

It's 4 wheel drums so I don't think I need a prop valve if I keep them, but I might upgrade to front wheel discs in the future so I was thinking to buy a kit that includes one I can use later.

Here's some examples:

ZINC MOPAR 8" Brake Booster Master Cylinder Bracket Dodge Plymouth A B E Body | eBay
Mopar A B E body power brake booster and master cylinder with pro valve pv2 | eBay

My understanding is that with the brackets shown the booster will just bolt to the old MC holes. I would just buy a stock booster from the parts store, but then I would need to find these stock brackets. Another thing, will there be enough vacuum to operate the booster without changing anything else?

Sorry for the # of questions, I haven't messed with brakes much before. Thanks!
 
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You will for sure need a prop valve either factory or an adjustable ones. The pressures are different for front disc/rear drum than the 4 whee drum.

Your best bet (and likely the cheapest, easiest option) is to google Dr Diff. He’s a forum member but is one of if not the leading brake expert for Mopars. Nice guy, he’ll get you going straight.

As for the eBay kits, hard to tell what’s in them consistently.
 
So, first thing. Adding a power booster isn’t actually upgrading the brakes. A power booster just makes the pedal easier to push, it doesn’t necessarily make you stop any faster. Yes, there can be a pedal or master cylinder ratio change involved there too, but you can change the master cylinder bore without going to power brakes and that does the same thing.

Next thing. I’ve converted my daily driver mopars from power brakes to manual. With the right master cylinder you get better pedal feel and brake modulation than with the factory style power brakes. I love manual disks with a 15/16” master cylinder. Works great.

So, if I was going to upgrade the brakes for a daily driver, I would spend my money on converting it to front disks, not converting it to power drums. The disks are more reliable, more consistent, and will perform better under daily driver conditions than the drums will.

That rebuild kit isn’t what I’d buy if you do decide to rebuild the drums. It seems to me like it includes stuff you probably won’t use like the wheel and master cylinder rebuild kits and is missing stuff you will likely need. You can buy a hardware kit for $5 a corner for the 10” drums from RockAuto. Heck new wheel cylinders are between 10-15 bucks depending on the size you want. If you don’t have a wheel cylinder hone the rebuild kits aren’t that useful. And if you need to replace any of the drums themselves, it could end up being cheaper to buy a disk conversion. Just my .02.

And DoctorDiff is the man you want to see if you are considering a disk conversion.
 
If I had to do it over again I would take the money I spent on the power booster and put it towards a 11” or 13” front disk brakes, and rear disk brakes along with the 15/16 master cylinder , all from the Doctor. With good disk brakes the power booster is overkill.
 
dukeboy_318 said:
You will for sure need a prop valve either factory or an adjustable ones. The pressures are different for front disc/rear drum than the 4 whee drum
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As for the eBay kits, hard to tell what’s in them consistently.
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I was thinking I wouldn't need one if I were keeping the drums, edited my first post just now to clear that up. Or would I still need it anyway? Either way, seems like disc brakes are the true safety upgrade here, so I'll look for an MC with a prop valve, or just the valve itself to add to the system.

72bluNblu said:
So, if I was going to upgrade the brakes for a daily driver, I would spend my money on converting it to front disks, not converting it to power drums. The disks are more reliable, more consistent, and will perform better under daily driver conditions than the drums will.

You can buy a hardware kit for $5 a corner for the 10” drums from RockAuto. Heck new wheel cylinders are between 10-15 bucks depending on the size you want. If you don’t have a wheel cylinder hone the rebuild kits aren’t that useful. And if you need to replace any of the drums themselves, it could end up being cheaper to buy a disk conversion. Just my .02.
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I think you've convinced me. I did think my truck with manual drums stopped just fine, now it makes sense. If I'm looking to spend money on the Dart's braking system, front discs should come first then. I'll call the # on Dr Diff's website on Monday and see what I can get. Hopefully I can get the hoses and fittings shown in the ebay rebuild kit from RockAuto as well, I really want to make sure that any trash in the old lines/system don't get into any new parts before I'm done replacing everything.

Thanks everyone for the input.
 
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zackw said:
I was thinking I wouldn't need one if I were keeping the drums, edited my first post just now to clear that up. Or would I still need it anyway? Either way, seems like disc brakes are the true safety upgrade here, so I'll look for an MC with a prop valve, or just the valve itself to add to the system.



I think you've convinced me. I did think my truck with manual drums stopped just fine, now it makes sense. If I'm looking to spend money on the Dart's braking system, front discs should come first then. I'll call the # on Dr Diff's website on Monday and see what I can get. Hopefully I can get the hoses and fittings shown in the ebay rebuild kit from RockAuto as well, I really want to make sure that any trash in the old lines/system don't get into any new parts before I'm done replacing everything.

Thanks everyone for the input.
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You’ll need the prop valve. Talk to Cass, aka Dr Diff, he’ll hook you up
 
Power booster kits on ebay used to be based on GM parts, I think, because the booster had a threaded rod to which they installed a Mopar adapter. But, the one you linked looks designed just for Mopar. The MC (bulgy) looks like one for GM, though I am no Chevy expert. Anyway, should be simple and should work. They didn't have those when I put power brakes on my 65 Dart, at least not affordably, so I re-purposed a booster MC from a 95 Breeze which I put on 74 Dart brackets. Also installed an adjustable prop valve (for future disks). The brake kit you linked shows pads. That might not be what you would get since front disks were fairly rare thru 1972 (Kelsey-Hayes & parts are hard to source today). I think you could get better prices by piecing together yourself on rockauto.
 
I have an SSBC disc brake conversion kit on mine. It uses GM booster and master cylinder as stated above. It was relatively expensive, but works well. Since I wasn’t going for an OE look, I didn’t care. I disagree on leaving off the power booster. I love the power brakes. Much less effort if you drive it in traffic. If it is just a trailer queen, maybe it doesn’t really matter.
 
Mike69cuda said:
I have an SSBC disc brake conversion kit on mine. It uses GM booster and master cylinder as stated above. It was relatively expensive, but works well. Since I wasn’t going for an OE look, I didn’t care. I disagree on leaving off the power booster. I love the power brakes. Much less effort if you drive it in traffic. If it is just a trailer queen, maybe it doesn’t really matter.
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I use my manual disk brake car as my daily driver. No issues. 15/16” master cylinder and away you go. It’s not a problem in traffic at all. There’s no way I’d go back to power brakes and that squishy, vague brake feel. You just have to size the master cylinder bore correctly for your brake set up.
 
Majority of disc brake conversions will change your front wheel bolt pattern from your OEM 5 on 4" w/ 7/16 lug studs, right hand threads on right side, left hand threads on left side,
to the 5 on 4.5" with 1/2" lug studs, right hand threads both sides.
2 spares and 2 lug wrenches?
There are a few aftermarket disc brake setups that do retain your OEM wheel bolt pattern. One of those adapts some Toyota rotors, calipers, and pads, but I'm not sure that works if you have 9X3 drum spindles. Good luck any way you go.
 
RedFish said:
Majority of disc brake conversions will change your front wheel bolt pattern from your OEM 5 on 4" w/ 7/16 lug studs, right hand threads on right side, left hand threads on left side,
to the 5 on 4.5" with 1/2" lug studs, right hand threads both sides.
2 spares and 2 lug wrenches?
There are a few aftermarket disc brake setups that do retain your OEM wheel bolt pattern. One of those adapts some Toyota rotors, calipers, and pads, but I'm not sure that works if you have 9X3 drum spindles. Good luck any way you go.
Click to expand...

Why two lug wrenches?

And they do make rims with BOTH patterns to simply the spare issue
 
I bought the scare bird kit for my daily driver. Huuuge improvement over the stock drums. It uses the stock 9 inch brake spindle and hubs, Toyota rotors, gm calipers, pads and brake hoses. I put an aftermarket adjustable prop valve inline to the rear brakes, and the car stops great.
I realize there are better options but I wasn’t ready to change the rear end yet and I needed new brakes bad. I used a stock replacement (for disk brakes) master cylinder for non-power applications. Putting power brakes on it would be a waste of time in my opinion.
I did get rid of all the left handed threads while I was at it
 
RedFish said:
Majority of disc brake conversions will change your front wheel bolt pattern from your OEM 5 on 4" w/ 7/16 lug studs, right hand threads on right side, left hand threads on left side,
to the 5 on 4.5" with 1/2" lug studs, right hand threads both sides.
2 spares and 2 lug wrenches?
There are a few aftermarket disc brake setups that do retain your OEM wheel bolt pattern. One of those adapts some Toyota rotors, calipers, and pads, but I'm not sure that works if you have 9X3 drum spindles. Good luck any way you go.
Click to expand...

The SSBC kit I have retains the small bolt pattern. Not saying that is necessarily a good thing, as most would probably rather go BBP, but just that it exists.
 
Does DrDiff's kit retain the small bolt pattern? I don't mind having either, since I like the steel wheels anyway and you can get them in different sizes. But I would be concerned about the spare only matching one axle...
 
dukeboy_318 said:
Why two lug wrenches?
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Because I said so thats why LOL
His OEM tire tool ( I should have said tire tool before ) wont fit the 1/2 lug nuts. A universal pattern spare wheel and a 4 way is a solution.
All the earlier posts were steering away from a vacuum assist/booster and toward disc brakes without mentioning the wheel bolt patterns, proportion valves, etc. I thought someone should.
I'll add one more point to ponder... Modern technology / anti-lock brake processors and those valves will alter, modulate, and redirect the fluid pressures that driver creates, yet the assist booster remains to do what it always did, reduce diver/pedal effort.
 
zackw said:
Does DrDiff's kit retain the small bolt pattern? I don't mind having either, since I like the steel wheels anyway and you can get them in different sizes. But I would be concerned about the spare only matching one axle...
Click to expand...
I’ve seen some kits that do, not sure if his does or not. Best to call him to be sure
 
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