Discussion Forum - Northstar Chevelle Club

4-door Chevelle · Super Poster

Converting to manual brakes

67ss · 1K+ Club

Have you bought about keeping the power brakes and add a vacuum canister to help with the low vacuum Of your new engine. Or an electric vacuum pump would also be a Comparable option by the time you buy all the other parts to swap it to manual.

4-door Chevelle · Super Poster

I do have a vacuum canister which only helped some with my current setup. My new setup will have even less vacuum. I am not opposed to an electric pump other than the cost. I should be able to buy the hardware for manual brakes under $100.

Lost in the 60s · President

Darren, most people go the other direction...

A manual disc set up is not something I remember seeing. The only difference I know of with the clevis from the pedal is that it goes in the upper hole of the pedal arm instead of the lower. The pushrod should be the same as any manual drum brake car. I understand the smaller bore master may provide less pedal pressure, but I can't say I endorse this, especially knowing you pull a camper. If this is because the vacuum will be too low with the new engine, Summit has a vacuum pump that works REALLY well to provide that vacuum for safe stops. I installed one on John's '72 when he had to have a 525hp 383 built. I know you're "frugal", but I would rather see you and the family safe...

http://www.summitracing.com/parts/sum-760152/overview/

Summit Racing SUM-760152 - Summit Racing® Electric Vacuum Pumps

It placed it under the fender and it isn't noticeable. I ran the vacuum hoses behind the fender also to hide them.

4-door Chevelle · Super Poster

What I am then curious about is what is an option for manual brakes on a front disc rear drum Chevelle?

4-door Chevelle · Super Poster

So, does the smaller diameter bore actually provide less or more brake pressure? Some part of me thinks or remembers reading I could get more pressure out of the smaller bore size. They do make both of course but I see a lot more of the larger bore size.

67ss · 1K+ Club

When going to manual brakes you go to a smaller bore diameter to build more pressure since you don't have a booster for aid in pushing the pedal. Then you also have to change what they call pedal to rod ratio on where the rod mounts to the brake pedal itself. Google it and all kinds of things explaining it should pop up.

Lost in the 60s · President

Here ya go, this answers all the questions. You need a manual master with 1" bore and deep rod hole. You also need to make certain it doesn't have the residual valve in the disc line and then buy a 2lb residual valve to plumb in, most likely along with a proportioning valve.

MBM Brakes, Steering, & Suspension

http://www.mbmbrakeboosters.com/index.php?option=com_content&view=article&id=7:master-cylinder-faq&catid=2:brake-boosters&Itemid=10

4-door Chevelle · Super Poster

I am headed over there to work on her this morning so will see if I can find the residual valve in the disc line.

Lost in the 60s · President

On original masters, the valve is part of the master. When installing a non-valved master, is when you need the in-line valve.

4-door Chevelle · Super Poster

I assume they did make a disc/drum setup that had a manual booster right? I think I have seen pictures of this type of setup. When I order a new master do I specify it to be valved for front disc rear drum?

Lost in the 60s · President

If you have the ability to spec it, yes, that would be cool. I'm not aware that we can spec anything on new masters, but it doesn't hurt to ask...

67ss · 1K+ Club

This should do what you want.

http://www.oreillyauto.com/site/c/detail/OBH3/101578/01292.oap?year=1974&make=Chevrolet&model=Malibu&vi=5157460&ck=Search_01292_5157460_3295&pt=01292&ppt=C0066

67ss · 1K+ Club

I also forgot to mention you need to move the rod to the upper hole on your brake pedal to change the pedal ratio.

Lost in the 60s · President

I didn't know if GM offered manual disc/drum brakes. That is useful information !!

He will need to plumb the disc brakes to the rear res on this one, right ?

67ss · 1K+ Club

Lost in the 60s wrote:
I didn't know if GM offered manual disc/drum brakes. That is useful information !!

He will need to plumb the disc brakes to the rear res on this one, right ?

No I don't believe the lines need to be switched. Here is an article I found that gives some good info.

http://www.mpbrakes.com/techtalk/master-cylinder-2/is-master-cylinder-change-required-in-drum-to-disk-conversion

Lost in the 60s · President

I don't see where that article address this, unless it went to another page that I didn't see. If the master is valved for hold back, putting the disc line on the drum side would hold too much pressure on the discs.
I have that same master on my '38 and the large reservoir line goes to the front discs as they need far more fluid capacity as the pads wear.

67ss · 1K+ Club

Sorry article was more for master cylinder sizing not to answer the line question. I have to look into your question more but what you say makes sense that you would want the bigger reservoir to feed the front.

-- Edited by 67ss on Friday 6th of May 2016 12:04:58 PM

bowtie · Secretary

Lost in the 60s wrote:
....... If this is because the vacuum will be too low with the new engine, Summit has a vacuum pump that works REALLY well to provide that vacuum for safe stops. I installed one on John's '72 when he had to have a 525hp 383 built. I know you're "frugal", but I would rather see you and the family safe...
http://www.summitracing.com/parts/sum-760152/overview/

How loud is this, can you hear it while everything is running? I think I've narrowed my brake problem down to needing either this or a canister, but the cost difference is huge.

Lost in the 60s · President

You'll never hear it once the engine is running. It's no louder than an electric fuel pump. I can hear it upon initially turning the key on without starting. It runs for a few seconds but draws the vacuum very quickly, which is where it will be far more effective than a canister. The can may be good for 1 or 2 applications but will run out of make up vacuum without having the engine rpm get high enough to replenish it. This turns on around 12-14", before you lose too much vacuum and pulls the system back down quickly. Even if the engine were to quit running, this will continue to run and provide vacuum assist.

Actually, John just had this situation 2 weeks ago. The screws on the rotor in the distributor had worked loose and one came out, allowing the rotor to flail around and break off the tab to the cap contacts. He had sudden and complete loss of the engine, but was able to make a safe, controlled stop with the brakes working normally.
He had his son with him at the time and was VERY glad he had this on the car.

I'm gonna throw a little guilt trip out here because there is no place for frugal when it comes to brakes. The safety of yourself, anyone with you and any other innocent people around your vehicle should far outweigh a couple hundred dollar part...

bowtie · Secretary

I hear ya, that's why I'm still trying to decide. My brakes work OK, but like you describe, that would be a very high positive selling point for an electric pump. Currently looking into another option: Some GM vehicles have small vacuum pumps on them, too.

Lost in the 60s · President

I don't want to start a controversy and I know money is always a consideration and we tend to think, "if I can save a few bucks on this, I have more for that". I'm guilty of it too, I have a "few" cars I'm buying stuff for almost constantly and can forget to weigh in safety as a factor.

If you find a good factory alternative to the aftermarket, that was similarly priced, that would be something for others to consider too..

4-door Chevelle · Super Poster

Lost in the 60s wrote:
You'll never hear it once the engine is running. It's no louder than an electric fuel pump. I can hear it upon initially turning the key on without starting. It runs for a few seconds but draws the vacuum very quickly, which is where it will be far more effective than a canister. The can may be good for 1 or 2 applications but will run out of make up vacuum without having the engine rpm get high enough to replenish it. This turns on around 12-14", before you lose too much vacuum and pulls the system back down quickly. Even if the engine were to quit running, this will continue to run and provide vacuum assist.

Actually, John just had this situation 2 weeks ago. The screws on the rotor in the distributor had worked loose and one came out, allowing the rotor to flail around and break off the tab to the cap contacts. He had sudden and complete loss of the engine, but was able to make a safe, controlled stop with the brakes working normally.
He had his son with him at the time and was VERY glad he had this on the car.

I'm gonna throw a little guilt trip out here because there is no place for frugal when it comes to brakes. The safety of yourself, anyone with you and any other innocent people around your vehicle should far outweigh a couple hundred dollar part...

This situation actually supports my idea of going back to manual brakes. My previous Chevelle had manual brakes and 4-wheel drums but I had no issues with braking as my leg worked just fine. With power brakes if your engine is no longer providing vacuum to the booster you REALLY have to stand on the pedal to get just SOME braking power.

So, if I go to U-Pull is there some vehicles that would have an electric vacuum pump?

bowtie · Secretary

I haven't looked too far into it, but specifically an 11 Chevy Cruze, 12 Sonic and 13 Malibu all have them (different part numbers for whatever reason). I'm sure others in the same build era would, and there's probably more too. I also found Hella #UP28 in the aftermarket.

Curious to see, but I think they have built in pressure switches.

4-door Chevelle · Super Poster

After all this discussion the electric pump may actually be my best option. It may also be a little less work so I am going to see what is out there.