Newbie brake question

[Steven S.]

Hi, I'm new to this forum. Been part of the Corvette Forum for a while. I've got a 65 driver, and I'm converting to PB with generic 67 parts (dual MC and Booster) The question is, do I need the distribution block that I see on some cars, or can I run the lines right to the MC? Is that only nessecary for the brake light sensor? Do you think a proportioning valve would help too?

Steve

[Bill M.]

Re: Newbie brake question

I converted my '65 power brake car to a manual brake car using a '67 dual master. I ran the lines straight to the master...no problems.

A proportioning valve is used when you have drum rears; I don't think it's necessary for disc rears.

[Gary C.]

Re: Newbie brake question

Steven, converted my '64 to '67 PB dual master cylinder with disc brakes in front. Kept rear drum brakes and if you do you will definetely need a proportioning valve. One BIG thing I ran into is the '67 PB dual master cylinder tilts upward too far and the stock hood wouldn't close. Gary....

[Joe L.]

Re: Newbie brake question

Hi, I'm new to this forum. Been part of the Corvette Forum for a while. I've got a 65 driver, and I'm converting to PB with generic 67 parts (dual MC and Booster) The question is, do I need the distribution block that I see on some cars, or can I run the lines right to the MC? Is that only nessecary for the brake light sensor? Do you think a proportioning valve would help too?

Steve

Steve-----


You do not need a distribution block and pressure differential sensing switch. There are only 2 reasons I can see to use one:

1) you wish to have pressure differential sensing information for safety purposes. However, if you do this you'll also have to wire a warning light into the system, too;

2) you wish to use pre-bent brake lines available from aftermarket sources for the 67 and later configuration. However, you should be able to use pre-bent brake lines for the 1965 or 1966 with PB application with adapters for the connection to the master cylinder and, possibly, other slight modifications.

You do not need a proportioning valve. No proportioning valve was ever originally used for any 63-77 Corvette with standard brakes or J-50 power brakes. Only 1966-68 with J-56 had a proportioning valve (adjustable) and 78-82 had a combination valve with a fixed-rate proportioning function. The latter was added due to the increase in the weight of 78-82 Corvettes without any other basic change in the braking system.

[Joe L.]

Re: Newbie brake question

Steven, converted my '64 to '67 PB dual master cylinder. Kept rear drum brakes and if you do you will definetely need a proportioning valve. One BIG thing I ran into is the '67 PB dual master cylinder tilts upward too far and the stock hood wouldn't close. Gary....

Gary-----


Now that surprises me. The master cylinder inclination is controlled by the firewall and power brake booster installed position. I don't think there's that much difference in the length of the 1965-66 power brake master cylinder and the 67+ style master cylinder. Plus, the 1967 master cylinder worked just fine for 1967 with the same booster as used for 63-66. So, I don't understand why the end of the master cylinder would hit the hood.

It may be that the 64 hood, being different than the 65-67 hoods, was the reason the interference occurred. However, since the car in this case is a 1965, I would not expect that problem.

[Gary C.]

Re: Newbie brake question

Joe, the mount holes appear to be higher up on the firewall in my '64. That's the only reason I could figure out. Perhaps someone with more C2 knowledge can provide a better answer. Definetely, needed the porprotioning valve with disc fronts and drum rears. Gary....

[Steven S.]

Re: Newbie brake question

Joe,

Thanks for the advise. Glad to hear that the hood is not an issue. I'll run the lines straight to the MC. Would you replace the front distribution block with one for a 67 with 3 holes instead of 4? What size lines would you use? Right now it looks like 1/4 from the single MC to the block and 3/16 from the rear to the fromt block. Thanks!

Steve

[Bill M.]

Re: Newbie brake question

Joe,

I'll run the lines straight to the MC. Would you replace the front distribution block with one for a 67 with 3 holes instead of 4? What size lines would you use? Right now it looks like 1/4 from the single MC to the block and 3/16 from the rear to the fromt block. Thanks!

Steve

The dual-circuit systems use 3/16 only. You will have to change the distribution block to a 3-hole. Maybe get a '65 power brake block? That's a dual-circuit system. I didn't have to change my '65 power block to go to the '67 manual master.

[Joe L.]

Re: Newbie brake question

Joe,

Thanks for the advise. Glad to hear that the hood is not an issue. I'll run the lines straight to the MC. Would you replace the front distribution block with one for a 67 with 3 holes instead of 4? What size lines would you use? Right now it looks like 1/4 from the single MC to the block and 3/16 from the rear to the fromt block. Thanks!

Steve

Steve----


I agree with Bill's advice. Basically, I would use the 1965 power brake distribution system modified as necessary to work with the 67 master cylinder.

One important point here: the 1967 dual master cylinder will provide additional safety inherent in a dual master cylinder system. However, I don't think you can expect much greater braking performance. I have always found that there just wasn't a great braking performance difference between any C2 or C3 standard versus power brake system.

[Joe L.]

Re: Newbie brake question

Joe, the mount holes appear to be higher up on the firewall in my '64. That's the only reason I could figure out. Perhaps someone with more C2 knowledge can provide a better answer. Definetely, needed the porprotioning valve with disc fronts and drum rears. Gary....

Gary-----


Yes, a proportioning valve is required when converting any pre-1965 Corvette to front disc/rear drum. In PRODUCTION, of course, Corvettes never used a hybrid system like this so no proportioning valve was necessary. When modified to this configuration, a valve is necessary just as it is on most other cars that were originally built with hybrid systems.

[Larry S.]

Re: Newbie brake question

Steve----


I agree with Bill's advice. Basically, I would use the 1965 power brake distribution system modified as necessary to work with the 67 master cylinder.

One important point here: the 1967 dual master cylinder will provide additional safety inherent in a dual master cylinder system. However, I don't think you can expect much greater braking performance. I have always found that there just wasn't a great braking performance difference between any C2 or C3 standard versus power brake system.

Joe, I haven't driven a power brake equipped C2 since 1986 when I foolishly sold my '66. I remember 50's and 60's power brakes being very sensitive--a light tap and you nose-dive. I was considering adding power brakes to my '67, but I'm going to reconsider if there's not that much difference. Is my memory just faulty? BTW, I sincerely respect your knowledge of Corvettes.

[Joe L.]

Re: Newbie brake question

Joe, I haven't driven a power brake equipped C2 since 1986 when I foolishly sold my '66. I remember 50's and 60's power brakes being very sensitive--a light tap and you nose-dive. I was considering adding power brakes to my '67, but I'm going to reconsider if there's not that much difference. Is my memory just faulty? BTW, I sincerely respect your knowledge of Corvettes.

Larry-----


Many 50's and 60's cars definitely did have power brakes that brought one to a lurching stop with just the slightest touch. I remember them well. However, Corvettes were not like that. At least, 65-82 are not like that. I'm not sure about the drum braked 63-64 with power brakes, but I expect that were about the same as later. I can barely tell any difference in braking for 65+ with standard brakes or power brakes.

[Larry S.]

Re: Newbie brake question

Larry-----


Many 50's and 60's cars definitely did have power brakes that brought one to a lurching stop with just the slightest touch. I remember them well. However, Corvettes were not like that. At least, 65-82 are not like that. I'm not sure about the drum braked 63-64 with power brakes, but I expect that were about the same as later. I can barely tell any difference in braking for 65+ with standard brakes or power brakes.

Thank you, Joe, for the insight. My '67 with standard brakes doesn't required that much effort, but I thought that power brakes might make a significant difference. Perhaps I was being 'option-minded', too. I think I'll just leave her the way it is. Thanks again.