66 2 Disk conversion and residual/Proportioning - Impala Tech
Brakes & Suspension Conversion Questions & more

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post #1 of 14 (permalink) Old 12-03-2019, 09:57 AM Thread Starter
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66 2 Disk conversion and residual/Proportioning

I'm in the process of converting my 66 impala SS Coupe to front disks via the C3 corvette spindles and single piston calipers.




Still need the Calipers, pads, bearings etc...

Looking through the posts not many people comment on how they did their Master cylinder Setup.

I currently have 1966 standard drums with power vacuum assist on all 4 corners and plan on keeping the rear drum setup. I am Keeping my stock booster.

My plan on the Master is to upgrade to a 68/69 impala Power Disk/drum Master cylinder from Rock auto.

Somthing like this...

Rock auto part number - ACDELCO 18M1036 {#19106822, 19176594} $43.00



But does that have a built-in residual pressure valve?? Do any that you buy at the store? How do you tell?

My question that big Dave somewhat answered in this post - https://www.impalas.net/forums/13-br...65-impala.html

MORE QUESTIONS: What about Residual valve and proportioning valves?

- What did the 69 impala use when it came factory with front disks?

I'd like to keep it factory looking even though a 66 did not come with Disks.

I see a lot of guys a show and cars and coffee use the generic valve with the given booster as seen below but is there a factory way of supplying the correct pressure to the drums?



https://www.speedwaymotors.com/GM-Di...lets,9878.html

Is this the Factory type option of disk/drum residual valve?



Which they do sell at Jegs etc... but is $40 by it self

https://www.jegs.com/i/JEGS/555/631300/10002/-1

In addition to that was there a factory Proportioning Valve?

I see the above "Generic" Valve does have proportioning but what was used in a factory car. I know the easy and cheap way would be to use the generic valve but I just wanted to know what was used in a 68-70.

I assume the Factory 68--70 B-body chevy with front disks used a different dist block too? Like below?



or this



Trying to get all the parts I need before I rip into this...

Ted

Last edited by brickwhite; 12-03-2019 at 10:47 AM.
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post #2 of 14 (permalink) Old 12-03-2019, 11:13 AM
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Drum Brakes have a fifteen to eighteen pound Residual Valve to keep the shoes close to the drum to reduce reaction time (this is a safety issue). Disc brakes have a two pound residual valve, but they operate at 1,500 to 3,000 pounds of line pressure. If you left the drum brake residual valve in the system the calipers would be dragging constantly.

The Proportioning Valve is in fact an orifice that slows down the pressure build up to the rear drums. This is because the factory uses huge springs to pull the shoes off of the drum because drum brakes are self activating and operate at 500 to 700 psi. If the fluid rushed back without the proportioning valve then the rear brakes would instantly lock up causing an uncontrolled skid.(This is a safety issue)

Pascal's law states that the pressure applied to the wheel cylinders is proportional (ratios of big to little). This is a mathematical relation ship that determines whether you have brakes or not! (this is definitely a safety issue).

You have to keep all of the parts together. Cheap brake kits use G-body metric calipers that had less volume due to a smaller diameter piston. The master cylinder had a smaller bore with smaller pistons to match it. The next step up on brake kits in price uses 1969-75 A and F body GM parts that have a larger "English" caliper piston that requires a matching larger bore master cylinder. The factory used a Y body (aka Corvette even though back in 1969 a Y body was a Corvair).four piston fixed bridge Girling style calipers that had a much larger volume in the caliper when you added up all of the piston diameters. It had a huge master cylinder that held a huge volume of brake fluid in it's reservoir to feed the big bore pistons.

You can not mix and match factory parts based upon price. (This is a safety issue)

All of the factory vales and the line size (the ID of the brake tubing) was matched mathematically by engineers to obey Pascal's law governing hydraulics. This was done to provide brakes that worked as intended.

Finally you have aftermarket parts designed by Wilwood and Baer. They were designed and sized by engineers to safely stop a 3200 pound car traveling at 170 mph. You can not mix and match their parts either. You buy everything you need in the form of a kit.

The 1967-'69 four piston brakes on the Impala required a special steering knuckle and a special hat to hold the wheel bearings (different size than stock bearings) that are not reproduced or offered as a service part. Everything else is offered as they are reproduced as a Corvette part.

Big Dave

Last edited by Big Dave; 12-03-2019 at 12:28 PM.
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post #3 of 14 (permalink) Old 12-03-2019, 02:34 PM Thread Starter
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brakes...

Dave, thanks for the reply.

Quote:
=Big Dave;227008]Drum Brakes have a fifteen to eighteen pound Residual Valve to keep the shoes close to the drum to reduce reaction time (this is a safety issue). Disc brakes have a two pound residual valve, but they operate at 1,500 to 3,000 pounds of line pressure. If you left the drum brake residual valve in the system the calipers would be dragging constantly.

Using a dual master wouldn't the pressure in the line be separate Front to Rear? Disk vs drum.

I understand that a 15/18lb or so residual valve is need to hold the pressure on the drum. Those individual valves can be purchased.

https://www.summitracing.com/parts/wil-260-13784 is a $20 10lb valve.

Some stated that the OE type Master from the 68 car had res valve built-in, just wondering if that is true?


With these old cars people mix and match parts all the time. I can mix a 1 1/8" cardone Master cylinder with a Willwood front caliper kit. I've seen it done. I'm sure Willwood would rather you buy their Master because it's $400. Or their front disks at $900. (it may not be the safest, I understand)



If you get the calculation correct, which shouldn't be that hard, you can have a car that stops very well with parts you can get at any supplier. Wilwood, Baer, AC delco, cardone, etc.



I was just trying to see what others have done and if they used a C3 corvette front brakes on their Impala because that's what I'm going to use.


Quote:
The 1967-'69 four piston brakes on the Impala required a special steering knuckle and a special hat to hold the wheel bearings (different size than stock bearings) that are not reproduced or offered as a service part. Everything else is offered as they are reproduced as a Corvette part.
Yep, this is why I'm using the C3 corvette spindle with my impala steering arm (have to cut the stop).

Ted
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post #4 of 14 (permalink) Old 12-05-2019, 04:14 PM
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I like the way you're going with the C3 stuff and the 69/70 MC but I'm just not knowledgeable on the residual valve. Sorry man.

HOW A NOVICE REBUILDS A 66 IMPALA CONVERTIBLE:
http://www.impalas.net/forums/blog.php?u=1432
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post #5 of 14 (permalink) Old 01-13-2020, 10:32 AM Thread Starter
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Here is the mess of brake lines and proportioning valves I have to work it... I'll get it sorted.

But as for the C3 brakes. This is what I'm using. Above you saw what I found on Ebay and now it's cleaned up with new paint and bearings.



couple odd one off things...

The biggest problem I've faced so far is the Castle nut for the C3 spindle... I think it is a 27/32" nut but I haven't been able to confirm. I bought a 3/4-20 castle nut but that is too small. The corvette part sites do not give specs on the ones they sell. But 63-68 corvettes used a different spindle than the 69-82 vette. The local FLAPS did not have them nor did they want to look... Dying breed. Napa and Orielly...

The large bolt that holds the caliper bracket and shield to the spindle in the middle circled in RED it a special buy item that did not come with my spindle.

https://www.zip-corvette.com/65-82-f...unt-bolts.html ($15 + shipping)

-Also you will need 4 the caliper bolts with lock washers (7/16"-20 x 1.25")

The steering arms (circled in orange) will work from your impala but will need to be altered to fit the disk caliper bracket. Either cut the nub off the arm (orange line )or grind on the caliper bracket.

- dust shield gasket $10

- Dust shield $30 each if you want dust shields go mine off Ebay, there are 2 different ones but they fit the same. One is gold one (76-82) is silver (69-75) that is the only difference.
https://www.zip-corvette.com/65-76-f...st-shield.html

I went for the re-sleeved lip seal C3 4 pistion calipers. They were about $120 each with the core charge. I know people say to find the single piston caliper but they are hard to find.

- Pads

- bearings, bearing seal

- new wheel studs

mock up.









not sure but the brake line maybe too short...that's full extension



The 4 pot calipers look good though...



BA. likes this.

Ted

Last edited by brickwhite; 01-13-2020 at 01:09 PM.
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post #6 of 14 (permalink) Old 01-13-2020, 03:29 PM Thread Starter
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but the big question.... will the caliper clear my 15x8 steel wheels???

NOPE!

Ted
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post #7 of 14 (permalink) Old 01-13-2020, 03:54 PM
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I have a 69 that came with factory disc brakes which I rebuilt stock when I first got the car. The stock 69 setup does have a separate residual pressure valve for the rear drums.

A factory single piston caliper will clear 15" wheels. That's what originally came on disc brake cars.

I've since converted to C6 brakes and have the calipers, bracket, MC, and pressure valve sitting around somewhere in a bucket. It all has about 1500 miles on it.

1969 Impala convertible build thread here:
https://www.pro-touring.com/threads/...ghlight=impala
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post #8 of 14 (permalink) Old 01-13-2020, 03:59 PM Thread Starter
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I'd be interested in the stock residual pressure valve and MC if you are willing to sell it.

Thanks,

Ted
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post #9 of 14 (permalink) Old 01-13-2020, 04:22 PM
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Corvette brakes require Corvette rally wheels to clear. They are similar in appearance on the car, but differ in the mounting step for tire installation that is rolled into the wheel.

I like you thought any 15" x 8" wheel would have come off of a Corvette, and as such clear the Corvette's Girling four piston calipers. Are your wheels stock Kelsey-Hayes wheels with a GM part number and date code stamped into them?


Big Dave
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post #10 of 14 (permalink) Old 01-13-2020, 04:32 PM Thread Starter
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My 17" fit just fine, But the 15x8 steel wheels are Not corvette rally wheels nor did I think they were. I wanted a non rally in 15x8 to go on the car.

I'll get them to fit.

Thanks for your help Dave.

Ted
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post #11 of 14 (permalink) Old 01-14-2020, 10:26 AM Thread Starter
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I found the correct Spindle nut for a C3 spindle.

It is a 27/32" x 20. Dorman part number - 05110

If anyone goes down this road and needs it.

I had to search quite a bit to find the size and none of the parts store guys knew what I was talking about nor would look.




Ted
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post #12 of 14 (permalink) Old 01-16-2020, 12:25 PM Thread Starter
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Quote:
Originally Posted by 67SS View Post
You don't need the residual valve as the most disc/drum M/C's have one inside the port for rear brakes. This is why all conversion kits do not have a residual valve included.

Disc brakes do not use residual valve, there will be one on drum brakes to reduce the reaction time for shoes to meet the drum. On disc brakes there is nothing to retract the piston and the pads are always in contact with the rotor. On drums, the shoes are self energizing which means the shoes are semi floating and when applied they wedge themselves into the drum to assist in braking. The shoes have heavy springs to pull them away when not engaged so they won't engage if slightly dragging. The residual check valve keeps some hydraulic pressure applied to keep the shoes slightly in contact but not engaged.

Which DISK/DRUM Master Cylinder should I purchase then?

Most of the parts places I've talked to don't know what they are talking about and the details on online part retailers don't necessarily say.

How do I know which MC is for DISK/DRUM?

Some people say that if it has a large front and small rear Reservoir the its for disk/drum.

like this

WAGNER MC101254 {#19176488, F101254, J8126739} Info
1-1/8" Bore; Vacuum Boost



Or if you go to summit MCs for a late 60s Chevy should work....



What about Bore? Should I go 1" bore or 1 1/8"??

I just want to buy what's going to work the first time...with decent pedal feel. I still need to look at my booster and old MC to see how long the push rod is.

As for what I ordered....



But this is what Came in via UPS...





I think it should work with disk/drum.... ????

Has the deep pocket like I need.

Seems my old MC was leaking anyway.






Ted
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post #13 of 14 (permalink) Old 01-16-2020, 02:32 PM
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There are residual valves on factory installed disc brakes: not to keep the pads in contact with the rotor, but to keep water from being forced into the caliper past the seal when driving through water. The reason there is no residual valves on brake kits is that they cost money; and they want to optimize their profits. They also correctly assume that you will not be driving through deep puddles with your prized Impala, nor even taking it out of the garage on a rainy day.

But yes if you are working with a factory system there is a residual valve specifically for disc brake cars. It can not be used with drum brakes, nor should a drum brake residual valve be used with disc brakes (there is a specific combination valve for a drum/disc system). The Corvette from 1965 on was equipped with four wheel disc brakes; without a proportioning valve bur using a residual valve (it didn't work as well as intended as the cast iron calipers and the aluminum pistons always corroded.

In Tampa it rains 60 inches of rain during the five summer months. Because the cities in the Tampa Bay area were built without any planning or city services the roads flood daily and Corvette owners have no choice but to drive through 14-18" inches of fresh water. Because of this the first stainless steel sleeveing of Corvette brakes started in Clearwater, FL.

The situation is improving slowly and a lot of the newer areas have storm drains now, but due to price of real estate and the fact that no one wants a road dug up a lot of the older areas don't. So come the rainy season I love to watch Asian import cars with their under the front bumper cold air inlets hydro-locking as the their owners drive through water above the top of their wheels. People used to come to my shop door wanting an engine rebuild. But due to the issue of getting parts I turned them down.

Big Dave
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post #14 of 14 (permalink) Old 01-16-2020, 03:25 PM Thread Starter
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I'm glad I don't live in Florida.

Ted
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