63 SWC: Advice on Brake Changes

[Jason S.]

[Joe L.]

Re: 63 SWC: Advice on Brake Changes


Jason-------


1) I would not even consider a swap involving retrofitting front disc brakes to a car originally built with 4 wheel drums. Such a hybrid system was NEVER originally used for a Corvette and I wouldn't want to try it now. I know some folks have done this but I NEVER would. A hybrid system also causes other complexities that are not worth getting involved with. A 4 wheel drum system will work just fine if all the parts are in good condition.;

2) You would most likely not need to add power brakes whether, or not, you were to add front disc brakes. However, I can't say, for sure, since I have no experience (and wish no experience) with a Corvette with a hybrid brake system. Power brakes are not a fundamental requirement of a hybrid brake system, though;

3) I don't think that going to a 1" bore master cylinder from the 7/8" is going to create a need for power brakes or is going to greatly increase pedal effort. There will be some pedal effort increase but I don't think it will be great. However, I would look more to see if I could come up with a kit with 7/8" bore master;

4) I don't think you need to add a system with a proportioning valve. Very few Corvettes were ever equipped with a proportioning valve.

5) While a dual master cylinder system definitely provides additional safety, if you have a single master cylinder system with all components in good working order, I don't see why you should need to convert to a dual system. Single master cylinder systems were used for years and very few folks experienced brake failures. I realize that you have had brake failures but I've got to believe that your system had serious deficiencies for this to occur. Your brake system needs to be in tip-top condition at all times. When possible, always replace with NEW components rather than rebuilt. If you do this, I don't think you'll ever have a problem, even with a single circuit system.

[Loren L.]

Re: 63 SWC: Advice on Brake Changes

My question is far more simple - why did you buy a '63 SWC instead of a 65-7?

[Jason S.]

Re: 63 SWC: Advice on Brake Changes

Interesting question. The car has been in the family since around 1980 - and I took ownership over in 2005. In those 9 years, I hate to say, it's been sitting in my garage more-or-less dormant as family needs have taken priority. I'm making going through the car and getting it back onto the road a priority now that some other priorities are out of the way. Plus......how can you not love the look of a '63 SWC? I've been looking at this car for 34 years now and still don't get tired of looking at that back end.........
I would love to have a '65 396 car, too, now that you mention it. I think they are way under appreciated compared to all the attention a '67 427 gets (same goes for a '66 427).

[Tracy C.]

Re: 63 SWC: Advice on Brake Changes

Jason,

Welcome to the NCRS. Don't get caught up in the "brake change" hype. For your intended use, the stock 4 drum system is more than adequate if in good working order.

Save your time and money,

Tracy

[Steve G.]

Re: 63 SWC: Advice on Brake Changes

The only advantage discs have over drums is their ability to dissipate heat. If you are not going road racing, your car will not stop any better with discs. The drums will easily handle all the heat you're ever going to make with them.

The dual circuit system, on the other hand does provide an additional measure of safety. Certainly maintaining the system significantly reduces the probability of issue, but there is still the unforeseeable.

I was in a 63 Impala that picked up a piece of wire in the driveshaft at the rear u-joint. We could hear this noise for a few mins then went away. No brakes at the next stop light. Took the yield way too fast, but managed to keep it upright. The wire had been hitting the rubber flex line and cut through it.

Would I do the dual circuit conversion? I'm not sure. For the little bit that I drive the cars and the roads I stick to, maybe not. Tough call.

[Jason S.]

Re: 63 SWC: Advice on Brake Changes

To both Steve and Tracy,
I think you are both grounding me - bringing me back to where my feelings were regarding the brakes a few weeks ago.
I, too, have been thinking that the drums should be just fine for a street-driven car, but conversations with a (albeit very reputable) vendor had me starting to think about the disk conversion while I am in the front suspension replacing bushings/springs/shocks, etc. anyway.
Doing the conversion was starting to make me concerned about originality (even though it will never be an NCRS car) - but at the same time all the negative talk regarding drums started making me think I should at least consider a swap while I had everything apart............
I like the way Tracy said "don't get caught up in the brake change hype" - I think that comment may have been spot-on.
What started me off on doing all this work was an unexpected brake fluid leak that caused me to completely lose brakes with the single-circuit system. This is what is still causing me to seriously consider the master cylinder upgrade - to have some redundancy in the system.

[Jason S.]

Re: 63 SWC: Advice on Brake Changes

Steve/Tracy,
If you also have a few moments, take a look at some thoughts I had in separate posts on suspension and exhaust improvements as well. I think I've likely made up my mind regarding exhaust vendors (Allen's) but am still on the fence for spring and shock changes. Those posts also start with the tagline "63 SWC......"

[Jason S.]

Re: 63 SWC: Advice on Brake Changes

Jason-------


1) I would not even consider a swap involving retrofitting front disc brakes to a car originally built with 4 wheel drums. Such a hybrid system was NEVER originally used for a Corvette and I wouldn't want to try it now. I know some folks have done this but I NEVER would. A hybrid system also causes other complexities that are not worth getting involved with. A 4 wheel drum system will work just fine if all the parts are in good condition.;

2) You would most likely not need to add power brakes whether, or not, you were to add front disc brakes. However, I can't say, for sure, since I have no experience (and wish no experience) with a Corvette with a hybrid brake system. Power brakes are not a fundamental requirement of a hybrid brake system, though;

3) I don't think that going to a 1" bore master cylinder from the 7/8" is going to create a need for power brakes or is going to greatly increase pedal effort. There will be some pedal effort increase but I don't think it will be great. However, I would look more to see if I could come up with a kit with 7/8" bore master;

4) I don't think you need to add a system with a proportioning valve. Very few Corvettes were ever equipped with a proportioning valve.

5) While a dual master cylinder system definitely provides additional safety, if you have a single master cylinder system with all components in good working order, I don't see why you should need to convert to a dual system. Single master cylinder systems were used for years and very few folks experienced brake failures. I realize that you have had brake failures but I've got to believe that your system had serious deficiencies for this to occur. Your brake system needs to be in tip-top condition at all times. When possible, always replace with NEW components rather than rebuilt. If you do this, I don't think you'll ever have a problem, even with a single circuit system.

Unfortunately I haven't been able to come up with a kit that has a Dual 7/8" MC. Based on my searches, I don't think I'm the first one to struggle with the question. There are plenty of people on the 'net searching for the same thing to no avail.

I do see Wilwood makes a 7/8" MC on their own - but it isn't part of any of the conversion kits that have custom bent lines specifically for the GM MC (they're probably close though). http://www.wilwood.com/MasterCylinde...temno=260-9439.

With that said, I have pointed out the fact before that the '63 Z06 had a 1" MC - but also had Power assist. I'm not sure if that was added to help assist the brakes when the metallic pads were cold, or to assist alleviating the pedal effort increase associated with the 1" bore, or a little of both, or another reason. I COULD add a '67 booster - which alot of kits offer - which would be functionally analogous to a Z06 (i.e., 1"+PB). But on a '63 that means I'd have to drill holes in the firewall and notch my hood......

So....since I'm so freaked out about everyone's warnings about pedal effort increases with a 1" dual master change, I'm left with 3 choices:

1) Also opt for the '67 style PB - Which could be functionally analogous to a Z06.
I don't want to do this, though, because I'd have to drill into the firewall and possibly notch my hood.

2) Use the 7/8" Wilwood M/C with no PB at all - which I'm sleeping on. I don't want to open my hood and see that though.........

3) Or just use the 1" Dual conversion as is. If a number of 65-76 non-power cars had 1" MCs on them, wouldn't my pedal effort be no worse than any of those (not sure if I'm comparing apples-to-oranges with a drum car vs disk with the differences in wheel cylinders vs calipers, I haven't tried that math)?

Or....maybe I'm just beating a dead horse..........

[Joe L.]

Re: 63 SWC: Advice on Brake Changes

3) Or just use the 1" Dual conversion as is. If a number of 65-76 non-power cars had 1" MCs on them, wouldn't my pedal effort be no worse than any of those (not sure if I'm comparing apples-to-oranges with a drum car vs disk with the differences in wheel cylinders vs calipers, I haven't tried that math)?

Or....maybe I'm just beating a dead horse..........

Jason-----

Yes, all 1965-76 Corvettes with standard brakes used a 1" master cylinder. If you were going to a 4 wheel disc brake system like all of those cars had, your braking performance would be no worse than those cars. I can tell you, for certain, that those cars with standard brakes brake very well. However, this is not what you would be doing. Your system would be a HYBRID system so I can't say, for sure, how that would work with a 1" bore master cylinder.

By the way, for what it's worth, I find very little braking performance difference between standard and power brakes for 68-76 Corvettes.

[Steve G.]

Re: 63 SWC: Advice on Brake Changes

Unfortunately I haven't been able to come up with a kit that has a Dual 7/8" MC. Based on my searches, I don't think I'm the first one to struggle with the question. There are plenty of people on the 'net searching for the same thing to no avail.

I do see Wilwood makes a 7/8" MC on their own - but it isn't part of any of the conversion kits that have custom bent lines specifically for the GM MC (they're probably close though). http://www.wilwood.com/MasterCylinde...temno=260-9439.

With that said, I have pointed out the fact before that the '63 Z06 had a 1" MC - but also had Power assist. I'm not sure if that was added to help assist the brakes when the metallic pads were cold, or to assist alleviating the pedal effort increase associated with the 1" bore, or a little of both, or another reason. I COULD add a '67 booster - which alot of kits offer - which would be functionally analogous to a Z06 (i.e., 1"+PB). But on a '63 that means I'd have to drill holes in the firewall and notch my hood......

So....since I'm so freaked out about everyone's warnings about pedal effort increases with a 1" dual master change, I'm left with 3 choices:

1) Also opt for the '67 style PB - Which could be functionally analogous to a Z06.
I don't want to do this, though, because I'd have to drill into the firewall and possibly notch my hood.

2) Use the 7/8" Wilwood M/C with no PB at all - which I'm sleeping on. I don't want to open my hood and see that though.........

3) Or just use the 1" Dual conversion as is. If a number of 65-76 non-power cars had 1" MCs on them, wouldn't my pedal effort be no worse than any of those (not sure if I'm comparing apples-to-oranges with a drum car vs disk with the differences in wheel cylinders vs calipers, I haven't tried that math)?

Or....maybe I'm just beating a dead horse..........

My calculations seem to show that going from a 7/8 to 1" bore will increase pedal effort by about 50%. That's a lot, but may not be excessive.

The thing to keep in mind about comparing disc to drums and power assist to not is that the disc didn't go to pb entirely because of the change in mc bore. Disc brakes are not self energizing where as drums are. With drum brakes of this type you have a primary shoe and a secondary shoe. As the primary shoe comes into contact with the drum it tries to rotate with the drum which applies the secondary shoe. Hence the self energizing or boost. When discs came out on some of the A body cars you could not order discs without power assist.

So just comparing 1" in pb disc to 7/8' in non power drums is not as straight forward as it seems. 7/8 manual discs would require much more pedal pressure than 7/8 manual drums. Adding the 1/8" to the diameter compounded the calculation.

Personally, I would research other GM vehicles of the era looking for one with a 7/8" bore and dual circuits. They are quite likely to have the same bolt pattern.

NB. Looked in my 67 Olds service manual. All cars with hd brakes used a 7/8 mc. All other drum brakes, power or manual used a 1". Disc brakes used a 1 1/8". I would bet that the hd mc would bolt right up.

[Jason S.]

Re: 63 SWC: Advice on Brake Changes

My calculations seem to show that going from a 7/8 to 1" bore will increase pedal effort by about 50%. That's a lot, but may not be excessive.

NB. Looked my 67 Olds service manual. All cars with hd brakes used a 7/8 mc. All other drum brakes, power or manual used a 1". Disc brakes used a 1 1/8". I would bet that the hd mc would bolt right up.

Actually, all other variables remaining the same, pedal effort would increase by 31% by changing from 7/8" to 1" - but I think you see my point. I'm basically interested in doing a dual circuit change without adding a PB, and ideally would like to find a dual MC that can retain the 7/8" bore so I don't have to deal with a pedal effort increase at all. So far I have not been able to find a GM 7/8" dual bore - and based on the number of other people on the 'net that have obviously tried this same mod before - other people have been met with the same lack of success. Some of them are on this forum as well.........

But then again......we've all been looking at alternative GM/Chevy MC's (Corvette, Nova, Camaro, etc) not necessarily parts from a B-O-P division. Thank you for the suggestion! Oddly that part of your reply never showed on my screen - I only saw it after I punched the "Reply with Quote" button. Hmmm.

So - with all that said.........I think I may still pursue the Dual Master conversions that several Corvette vendors sell - and then if my pedal effort is not to my liking, I either have your Oldsmobile recommendation to look after, or perhaps the Wilwood 7/8" part that is out there.

Thanks for the Oldsmobile input.

[Duke W.]

Re: 63 SWC: Advice on Brake Changes

The reason master/wheel cylinders fail is corrosion, which allows internal leakage. Corrosion is minimized over time if the fluid is flushed every two or so as recommended by some OEMs. ( but not GM).

Alternatively, completely rebuild all the hydraulic components, assemble with DOT 5 silicon fluid, flush all the pipes (and new hoses) with denatured alcohol and thoroughly dry. The purpose is to remove every remaining molecule of glycol-based fluid.

Then reassemble the system and fill with DOT 5 fluid. If you do everything right the chance of a hydraulic failure is extremely remote.

I recommend the above rather than trying to jury-rig a dual master cylinder.

Duke

[Jim T.]

Re: 63 SWC: Advice on Brake Changes

I like using DOT5 silicone fluid for brakes, even used it when I rebuilt a hydraulic operated clutch pedal. One thing to think about is in using the original type drum brake brake shoe linings that will use the same composition as originals for best braking. I use Bendix original type composition.

[Steve G.]

Re: 63 SWC: Advice on Brake Changes

Maybe I missed something earlier. Have you actually measured your mc? According to my 63 factory service manual standard and power brakes used the same 1" bore, the hd metallic brakes used the 7/8". You'd be fine using either one of those.

Yes, redid my math this morning and I don't know how I ended up with 50%. I should know better than to do arithmatic after happy hour.