Vacuum Booster or Not?

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PocketAces

PocketAces

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I'm going to be installing kelsey hayes disc brakes on my 65 Dart in the near future. I have a 1972 booster and master cylinder, but I'm trying to decide whether to use the booster. It's freakin huge and might look out of place under the hood of a 65.


Currently I have drums all the way around. 10" in front, 9" in the rear and a single circuit master cylinder. I'm getting used to the drum brakes. Maybe they're working better with use, or maybe my leg muscles are getting built up. But I'm sure I would never be happy with them. Someday my daughters will be old enough to drive the car but I wouldn't feel good about that with manual drum brakes.


My question is this: Will the braking effort be noticeably less just by upgrading to disc brakes and a dual circuit master cylinder? Or do I need the booster in order to notice a significant reduction in pedal effort?

I could try it both ways but I think that means buying another master cylinder and re-bending the brake lines. I would like to avoid doing the job twice.
 
I would go with power brakes when upgrading to discs on a daily driver.
Discs require more effort than drums so you will have to get even bigger leg muscles if you go the manual disc route.
My '65 Valiant has non power Kelsey Hayes discs from the factory. They do a good job of stopping the car but the pedal requires a lot of pressure so you don't get the feeling of having good brakes until you really step on it..

As much as I love the Kelsey Hayes brakes I might go for the later A-body single piston discs and BBP conversion if I was to upgrade a car that didn't have them allready. A much simpler design that works at least as well. The four piston KH calipers work good but have alot more moving parts and so are more complicated and expensive to work on.
 
Rocket-Racing said:
I would go with power brakes when upgrading to discs on a daily driver.
Discs require more effort than drums so you will have to get even bigger leg muscles if you go the manual disc route.
My '65 Valiant has non power Kelsey Hayes discs from the factory. They do a good job of stopping the car but the pedal requires a lot of pressure so you don't get the feeling of having good brakes until you really step on it..
Click to expand...

Thanks for the feedback. That's exactly what I was looking for.

Does your Valiant have the original single circuit master cylinder? I'm wondering if that has much effect on pedal effort.
 
if your upgrading to kelsey hanyes disc's I strongly advise you go with a dual circuit master cylinder. As far as the brake booster is concerned you don't need to but it makes a world of difference I couldn't find a vaccum booster around my area so I opted for hydroboost from a chebby diesel it runs off the powersteering to provide the pedal assist for the brakes
 
My wife's Dart has non-power discs. She thinks they work great and are easy to use.

Trust me..... If my wife isn't complaining, you will be fine with non-power too.
 
1968FormulaS340 said:
My wife's Dart has non-power discs. She thinks they work great and are easy to use.

Trust me..... If my wife isn't complaining, you will be fine with non-power too.
Click to expand...

Cool Info! I would love to eliminate the power booster from my system.

If it's not a daily driver, to me it seems better to go manual to eliminate the usage of vacuum and give you a better Idle quality etc. I'm no expert just thinking out loud.
 
I don't see a consensus forming. Some say disc brakes will increase pedal effort. Others say it will be reduced. The guy at Inline Tube recommends that I use the booster.

I want my pedal effort to go down. Maybe not as much as a modern car, but it has to be less than the current manual drums.

Thanks to all who replied. Keep the opinions coming.
 
If you want low pedal effort go with a 15/16" bore master cyl, that will give you the least amount of pedal effort without a booster.
 
daliant said:
If you want low pedal effort go with a 15/16" bore master cyl, that will give you the least amount of pedal effort without a booster.
Click to expand...

I found a few on Rock Auto that are 15/16" bore, but they're all for drum brakes and they appear to have equal sized reservoirs. Don't I need one with a larger reservoir for the front brakes?
 
Dorman part# M80266 bore= 15/16" w/disk brakes. With a small bore master cyl the effort will be easy but the trade off is a little extra pedal travel.
 
Will the Dorman M80226 work with manual brakes? It is listed on their site as power disc, looks like same mounting as standard brake master cylinder.
 
arveeotto said:
Will the Dorman M80226 work with manual brakes? It is listed on their site as power disc, looks like same mounting as standard brake master cylinder.
Click to expand...

I believe there could be differences between Power and Manual master cylinders regarding the way the push rod engages the Master Cylinder piston. I think I will go to an auto parts store and compare Manual and Power master cylinders to see what's up.
 
arveeotto said:
Will the Dorman M80226 work with manual brakes? It is listed on their site as power disc, looks like same mounting as standard brake master cylinder.
Click to expand...

I was looking at the linkage on the vacuum booster from the 72 dart. There is an arm that multiplies the movement of the brake pedal rod. For a given stroke of the brake pedal rod, that linkage gives more stroke on the rod coming out of the booster.

That explains why they used a larger bore on the manual cars instead of a smaller bore which is what you would expect. Because they needed more bore to move the same amount of fluid with a shorter stroke.

So does the 15/16" bore master cylinder move enough fluid without the added stroke of the power brake linkage? Maybe you just have be more vigilant to keep them fully bled?
 
I had a 15/16" bore, disk brake style master cyl on a 74 Dodge power wagon w/single piston disk on the front and it worked fine for me. The truck originally had a booster on it which I took off because it leaked. The master cyl had the recess for the push rod retainer so with the right pushrod it was good to go.
My daily driver 72 dart has a 1 1/16" master cyl in it and the pedal is a little on the stiff side to push but I dont mind it, if I had to change it I would definatly go with a small bore master cyl. I've never had a car with multi piston calipers on it so I dont know how much of a piston volume difference there is between the two different styles if any, but it doesn't take much fluid to compress the caliper when the brakes are applied. The rear brake adjustment shoud be kept up regardless of whatever style brakes the car has because this effects the pedal free travel.
 
I found another thread that has a lot of useful info on the subject.

http://www.forabodiesonly.com/mopar/showthread.php?t=27864&highlight=master+cylinder+push+rod

In this thread member redfastback recommends the same master cylinder, although again the application is not the 4 piston kelsey hayes calipers.

The thread concludes that the push rod from the manual brakes was reusable with the new master cylinder. But the car was not a 65.

I got busy and pulled the old master cylinder off the firewall and removed the push rod. Then I installed it into the master cylinder that came off a 72 Dart with power disc brakes. Not sure if it's the right one for that application, the bore is 1 1/32. The rod fit tightly into the master cylinder using the same rubber bushing from the 1965 master cylinder.

DISREGARD - SEE POST 17

The problem came when I hooked the push rod to the brake pedal. It was too short so that the brake light switch was not engaging. It would take at least 3/8" longer rod to fully engage the brake light switch at the end of travel. If I go without the booster, I will need to find a longer rod or lengthen the one I have by probably 1/2" Currently it's 6" from the center of the pin to the end of the rod.

Then I installed the vacuum booster on the firewall with the same master cylinder. Again when I went to hook up the brake pedal to the linkage, it was too short, this time by about 5/8". So if I decide to use the booster, I will have to lengthen the linkage by probably 3/4".

END DISREGARD

Having seen what the engine compartment looks like with the big old booster in there, I am highly motivated to try the small bore master cylinder. The master cylinder is very close to the breather it rubs the A/C lines at the front.

I would feel better if I could find someone who has used that master cylinder with Kelsey Hayes front disc brakes and no booster.
 

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So I put the old master cylinder back on with the old push rod and now the push rod is too short! The brake lights won't go out. I'm pretty sure I never moved the brake light switch, but maybe I did somehow.

If so that might invalidate my previous measurements. It's been a long day....
 
OK, this is embarrassing. Disregard everything in the last two posts.

I went back out to study the brake light switch problem. Turns out the bracket that holds the switch is adjustable. I must have moved it when I yanked up on the brake pedal to disengage the rod from the master cylinder.

I reinstalled the 72 disc brake master cylinder and verified that the 65 rod will work with this master cylinder.
 
I had original Kelsey-Hayes disc brakes on my '70 Duster that were manual and I liked it a lot. You definitely have to press harder than power brakes but the increased "feel" in the pedal is great. Really helps in low-traction situations (ice, etc.). I never felt like I needed more brakes either, I had enough stopping power to haul down from high speeds just as easily as any newer car. In fact I'm upgrading to '73-up disc brakes and I'll be keeping them manual.

Only crappy thing is heat buildup and fade, try to run wheels that ventilate the brakes. I had factory steel wheels and the brakes would get noticeably weaker after lots of stopping.

BTW if you want a big improvement in braking power get an adjustable proportioning valve; from the factory the rear wheels lock up WAY too easily and the fronts end up getting too little pressure before then.
 
MOPEkidD-3 said:
I had original Kelsey-Hayes disc brakes on my '70 Duster that were manual and I liked it a lot. You definitely have to press harder than power brakes but the increased "feel" in the pedal is great. Really helps in low-traction situations (ice, etc.). I never felt like I needed more brakes either, I had enough stopping power to haul down from high speeds just as easily as any newer car. In fact I'm upgrading to '73-up disc brakes and I'll be keeping them manual.
Click to expand...

Can you compare pedal effort for manual Kelsey Hayes discs to manual 4 wheel drum brakes?
 
65DartGTConv said:
Can you compare pedal effort for manual Kelsey Hayes discs to manual 4 wheel drum brakes?
Click to expand...

No sorry I've never had the chance to drive a manual drum-brake car... I'm sure others have though, hopefully they'll post on it.
 
MOPEkidD-3 said:
I had original Kelsey-Hayes disc brakes on my '70 Duster that were manual and I liked it a lot. You definitely have to press harder than power brakes but the increased "feel" in the pedal is great. Really helps in low-traction situations (ice, etc.). I never felt like I needed more brakes either, I had enough stopping power to haul down from high speeds just as easily as any newer car. In fact I'm upgrading to '73-up disc brakes and I'll be keeping them manual.

Only crappy thing is heat buildup and fade, try to run wheels that ventilate the brakes. I had factory steel wheels and the brakes would get noticeably weaker after lots of stopping.

BTW if you want a big improvement in braking power get an adjustable proportioning valve; from the factory the rear wheels lock up WAY too easily and the fronts end up getting too little pressure before then.
Click to expand...

If you really want them to not lock up use 13/16" rear slave cylinders if you have an 8-3/4" rear-end. Use 7/8" rear slave cylinders if you are running a 7-1/4" rear-end. There are other blogs on which part numbers these relate to.
 
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