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I am planning to up grade to 4 wheel disc brakes and I am looking for advice on the options we have for our Monte's

 

I plan to stay with the stock 15x7 rally wheels and would like to have at least a slotted disc if not slotted and drilled for both the front and rear. I want 2 piston calipers for the front but would settle for a single piston in the rear.

 

SSBC has a kit that includes everything for the front including a new 9" booster and master cylinder but they say that booster fits only the Chevelle and not the Monte. Does that make sense to anyone??

 

Baer has a kit that just slides onto the existing spindle but doesn't have any other pieces like the smaller booster and M/C and they appear to be about the same price. Is Baer better or just more expensive??

 

Any advice on your experience and the choices you made would be appreciated.

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my monte has 4 wheel disc stock setup in the front and ssbc kit in the back booster and master cylinder is from a 83 trans am which had 4 wheel disc.as far as the 9" bosster not fittin the monte dont believe that as the monte has the same firewall as the chevelle. the rear disc from ssbc will fit 15" wheels in the back.

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Not sure what those people did with the brakes on their cars but they may not have changed the Proportioning Valve. There is something wrong if you don't stop better with Disc's.

 

If for some reason it is the 9" booster that is a concern. The only reason I would consider changing the booster is for the size as it is tight with the BBC and tall valve covers.

 

I am modernizing the car with what is available these days. I have increased the power and acceleration with a now fuel injected BBC and a 700r4. I have increased the handling with Global West and Edelbrock control arms and sway bars. Now it is time to improve the stopping abilities of the car and slotted discs with aluminum multi piston calipers seems like the appropriate improvement.

 

What are the part numbers you guys used. I am looking at the A125-26 for the rear and the A123-1A for the front.

 

Were there any fitment problems or did those parts just bolt right in with no muss of fuss??

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colonel i used the proportioning valve that was on the trans am. here is a pic of my bosster carpics064-1.jpgfor my rear disc i used part # A125-3 as far as the front brakes they r the stock disc. if ur axle have c-clip eliminators the kit u r lookin at wont work.

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Is that a 9" booster with short valve covers???

 

It doesn't look like there is much more room than mine with an 11" booster and tall valve covers.

 

No worries about the c-clip eliminators, not using them.

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Hey Colonel, the difference is probably that Monte70car's valve covers are straight up and down, which has less clearance than normal BBC valve covers. Most of the ones you see aftermarket have an angle to the lower side, that gives you more clearance, and many have a top that peaks in the middle and tapers down towards the edges.

 

Something else you might look into if you're looking at getting better brakes is a dual diaphragm booster, they make dual 9" diaphragms which is almost a 25% increase in area over a stock 11"single diaphragm unit. Also, stock montes came with a 1 1/8" diameter master cylinder. You can get a 1" diameter MC that is designed to work with our cars from Master Power Brakes, or Classic Performance Products.

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I checked the gap today and I can just get my fingers between the V/C and the booster so maybe 3/4 of an inch. So you can see where that smaller booster would be nice.

 

Is that dual diaphragm booster much longer than the single??

 

Is it available from Master Power Brakes or Classic or is that only the smaller M/C.

 

Why would a smaller diameter M/C be better??

 

If I go with a smaller M/C I will need that extra booster assist or is my thinking off on that?

 

I got a friend here that is trying to get me to go for larger aluminum wheels now so I can get 12 or 13 inch disc's in the front now. I didn't plan on that or I wouldn't have sprung for recoating the original rally's and new BFG rubber. So now if I do that not only are the new wheels and rubber $2,000 but the 13 inch disc kit is $2,000 instead of the $ 1,300 I was planning on. Oh well there is still a couple feet of snow on the ground so I have some time before I can realistically get at the changes anyway.

 

Keep the advice coming if you got it though.

 

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I think a dual diaphragm is a couple inches longer than a single. The only real advantge is that you have extra room around your valve covers. a Dual 8" booster has about the same amount of diaphragm area as a single 11" booster, so the assist will be virtually the same. A Dual 9" booster has around 127 in^2 of area compared to an 11"s 95 in^2 of area, so you should get more assist out of a dual 9" booster. But, if you have too big of a cam and have no vacuum, no booster will work because they need vacuum to do anything.

 

A smaller bore MC will give you higher line pressure because of teh smaller bore.

 

Bear with me here. . .

 

 

Let's say you have a 5:1 pedal ratio. That means that where you put your foot is five times the distance from the pivot than where the master cylinder/booster connect to the pedal. So if you apply 100 pounds of force at the pedal with your foot, you would get 500 pounds of force pushing on the master cylinder and booster.

 

Then, let's pretend you don't have any power assist or booster. The area of a circle that has a diameter of 1.125 is .994 square inches. The area of a circle that has a diameter of 1" is .785 square inches.

 

If you have 500# of force pushing on the master cylinder that has a 1.125" bore (stock) you get 500#/.994 in^2 which gives you 503psi. If you have that same 500# acting on a 1" diameter piston, you get 500#/.785 in^2 which gives you 637psi. That's a 27% increase in brake pressure with the same pedal effort. The byproduct of that is a pedal the goes down a little further and has a softer feel. I am going to buy a dual 8" booster and a 1" MC from Classic Performance during the next couple weeks I think. CPP has a MC that they have designed based off of the GM master cylinders but with some small differences. They sell a MC/Booster/Proportioning Valve combo through summit pretty reasonably that is designed to work with Chevelles and our cars. If you use an 8" booster you get a 1" MC, if you get the 9" booster, I think you get a 1 1/8" MC. According to CPP, they make all of their own parts in house, and give a lifetime warranty on their stuff. Now, I don't know if their "in house" means that they have a shop in Korea or anything, but at least they seem to stand behind their stuff.

 

Here is the link to what I am going to use. Summit CPP MC/Booster combo

 

clp-6474bb2-8_w.jpg

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Allan, the volume of fluid needed is determined by the calipers used, and the wheel cylinders for the rear. Since those have stayed the same, they need the same amount of fluid. This is why the pedal on a smaller master cylinder piston unit goes down further than one with a larger MC piston. I've done a bunch of reading, and some people on the chevelle site have had issues with not being able to move enough fluid for their cars when going to a 1" bore. On the other hand, there are lots of other people on the same site that say the 1" bore unit works fantastic. I think that is why CPP has designed their own master cylinder, It may have longer stroke potential before the MC piston bottoms out, I don't know for sure. Master Power Brakes also has a 1" MC they recommend for our cars. They suggest a 1" MC if you wanted to use Non-Power brakes. The Chevelle guys are mixing and matching MCs from other cars to get a brake setup that they like, which might be one of the problems. If the car they took the MC off of had calipers that didn't need as much fluid volume, the MC might not be designed to move as much fluid as we would need with our brakes.

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I think when you are running disc's all the way around that volume is better than pressure especially when you use a booster that already increases your foot pressure beyond the original booster with Disc/Drum set up.

 

Great info though. Still have to make my decision as to which way to go.

 

Do 17 x 9 inch wheels with 40 or 50 series rubber fit under our cars???

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OK, I have decided what I am going to do. Thanks for all the info and ideas.

 

I have just ordered a 1 1/8" Master Cylinder and Chrome 9 inch Dual Diaphragm Brake Booster. Below is the webpage for the Master Cylinder. It is a spiffy all in one unit that will allow me to attain the exact split for braking force my Monte needs and have 1 less piece to plumb in to the setup.

 

http://www.classicperform.com/NewProducts/MCPV-1/MCPV-1.htm

 

They don't have a pic for the booster but you can find an 8 inch pic with the standard M/C on their site.

 

SSBC will be providing the front and rear kits I will use. The front kit (A123-21) below gives me a 12" rotor instead of the 11" one with the kit (A123-1A) I was originally planning on plus a 4 x 43 mm piston caliper for more even and added clamping force over the 2 x 43mm piston caliper with the 11" kit.

 

http://www.ssbrakes.com/products/detail/5870/?make=Chevrolet&model=Chevelle&year=1970

 

The rear kit (A125-26) has a parking brake all in the same caliper.

 

http://www.ssbrakes.com/products/detail/3250/?make=Chevrolet&model=Chevelle&year=1970

 

The front kit does require the addition of a specific front spindle and hub assembly from a company called American Touring Specialties. The "AFX" spindle (webpage below) saves some weight but more importantly it saves space allowing the use of the 12" rotors inside of the 15" Rally wheels that I really wanted to keep on the car and avoid springing for new 17" wheels and tires. Normally 12" rotors require 16" wheels and 13" rotors need 17" wheels.

 

http://store.nexternal.com/shared/StoreF...ount2=776969552

 

I plan to get some 60 - 0 numbers from my G Tech meter prior to the swap and compare them to the numbers after to quantify the value of the effort for this. I expect there will be some unsprung weight saving with this setup as well so I plan to repost on this same topic when I get it all completed.

 

Thanks again fellow Monte Lovers.

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