1973 Brakes
Thread Starter
Intermediate
Joined: Oct 2018
Posts: 39
Likes: 0
From: Jacksonville, FL
1973 Brakes
Hey!
I've got my C3 at a mechanic and one of the problems I wanted addressed was weak braking.
The mechanic says there's little that can be done because:
I know nothing about vacuum brake systems but, it seems to me that replacing the vacuum lines and an upgraded booster pump to compensate for lower engine vacuum would address this. Is my ignorance showing? Is there no such thing as an upgraded/more powerful booster? Is there an all hydraulic option? Something else I haven't thought if? It's a little scary to drive with the barking power it currently has.
I've got my C3 at a mechanic and one of the problems I wanted addressed was weak braking.
The mechanic says there's little that can be done because:
- The vacuum lines are old an leaking
- The high compression engine creates lower vacuum
I know nothing about vacuum brake systems but, it seems to me that replacing the vacuum lines and an upgraded booster pump to compensate for lower engine vacuum would address this. Is my ignorance showing? Is there no such thing as an upgraded/more powerful booster? Is there an all hydraulic option? Something else I haven't thought if? It's a little scary to drive with the barking power it currently has.
Race Director
Joined: May 2006
Posts: 18,689
Likes: 2,571
I believe you may need a better mechanic.
1. There is only one line for the brake booster and if bad can be easily replaced. If many hoses are leaking you would have other problems including poor engine performance, poor headlight opening and closing, poor windshield wiper door opening and closing, etc.
2. That statement makes no sense. A 1973 Corvette engine has low compression if unmodified either 8.5:1 or 9.0:1. By comparison my 1969 has 11:1 and has no brake issue.
1. There is only one line for the brake booster and if bad can be easily replaced. If many hoses are leaking you would have other problems including poor engine performance, poor headlight opening and closing, poor windshield wiper door opening and closing, etc.
2. That statement makes no sense. A 1973 Corvette engine has low compression if unmodified either 8.5:1 or 9.0:1. By comparison my 1969 has 11:1 and has no brake issue.
Last edited by MelWff; Aug 15, 2019 at 11:53 AM.
Race Director
Joined: Mar 2016
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From: Napa Valley California
To better answer this question we would need additional information about your 73.
Your mechanic could be completely correct.
A high lift hi-performance cam shaft and modified engine can produce low vacuum and could effect the vacuum needed to properly operate the power assisted brakes.
Many people on this forum and those who own other make and model cars with hi-performance modifications may run Hydro-boost hydraulic braking systems or vacuum pumps to obtain the necessary vacuum to operate their brakes and other vacuum needs.
Hydro Boost runs a hydraulic line from the power steering pump to the brakes system and eliminates the vacuum brake booster.
A vacuum pump runs off the electrical system and can be mounted just about anywhere.
If your 73 is mostly stock without performance modifications, then I would start looking into why you may be having vacuum issues.
Another issue with these Corvettes is getting the brakes to bleed all the air out of the system
There are numerous threads on this forum posted by members who have had nothing but poor braking problems due to the brakes not bleeding properly.
Once the brakes are properly bled, their brakes work perfectly.
Your mechanic could be completely correct.
A high lift hi-performance cam shaft and modified engine can produce low vacuum and could effect the vacuum needed to properly operate the power assisted brakes.
Many people on this forum and those who own other make and model cars with hi-performance modifications may run Hydro-boost hydraulic braking systems or vacuum pumps to obtain the necessary vacuum to operate their brakes and other vacuum needs.
Hydro Boost runs a hydraulic line from the power steering pump to the brakes system and eliminates the vacuum brake booster.
A vacuum pump runs off the electrical system and can be mounted just about anywhere.
If your 73 is mostly stock without performance modifications, then I would start looking into why you may be having vacuum issues.
Another issue with these Corvettes is getting the brakes to bleed all the air out of the system
There are numerous threads on this forum posted by members who have had nothing but poor braking problems due to the brakes not bleeding properly.
Once the brakes are properly bled, their brakes work perfectly.
Last edited by OldCarBum; Aug 15, 2019 at 12:18 PM.
Thread Starter
Intermediate
Joined: Oct 2018
Posts: 39
Likes: 0
From: Jacksonville, FL
Hydro-boost? Okay, this sounds interesting and I'm disappointed my mechanic hasn't brought it up.
Is that, essentially, making the brakes hydraulic vs. vacuum that they are now? Does it put extra stress on the power steering pump? Any estimates on what a conversion to hydro boost would cost?
Is that, essentially, making the brakes hydraulic vs. vacuum that they are now? Does it put extra stress on the power steering pump? Any estimates on what a conversion to hydro boost would cost?
Le Mans Master
Joined: Aug 2005
Posts: 6,521
Likes: 1,956
From: Temple Terrace Florida
The L-88s with 12.5 compression had no problem with their brake systems. Check for air in the system, or glazed pads and rotors. The stock Corvette brake systems worked well from 1965 to 1982. Jerry
Race Director
Joined: Jul 2004
Posts: 12,690
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From: Scottsdale Arizona
OldCarBum is right and your mechanic may be right. Or not (mechanic I mean).
weak brakes is pretty broad. Is your pedal going to the floor? Is your BRAKE light on when you press the pedal hard? Lots of shaking when you press the pedal?
Power brakes without the booster working properly should still work ok. If they don’t, I’d look elsewhere for the problem, like air in the lines, poor pads, bad rotors or a combination of the above.
weak brakes is pretty broad. Is your pedal going to the floor? Is your BRAKE light on when you press the pedal hard? Lots of shaking when you press the pedal?
Power brakes without the booster working properly should still work ok. If they don’t, I’d look elsewhere for the problem, like air in the lines, poor pads, bad rotors or a combination of the above.
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Instructor
Joined: Jun 2018
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Brake check
One simple test would be to pry off the brake booster line.
You should hear pressure escaping.
Also on my 73 I needed to buy this:
Along with a plate that covered the brake reservoir.
This allowed me to finally properly bleed my brakes and restore pedal feel.
Best investment .
Good Luck
You should hear pressure escaping.
Also on my 73 I needed to buy this:
Along with a plate that covered the brake reservoir.
This allowed me to finally properly bleed my brakes and restore pedal feel.
Best investment .
Good Luck
Last edited by mike914; Aug 16, 2019 at 08:59 AM.
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From: Grapevine Tx
2018 C3 of Year Finalist
2016 C3 of the Year Finalist
Let's start over.
Is your brake pedal spongy feeling, or do you just have to press real hard to stop. If your pedal is spongy feeling and goes all the way to the floor, you have air in your lines. Flush them and bleed them with fresh brake fluid.
If you just have to push real hard but not a spongy brake, then you probably aren't getting any boost. Is the brake feel/performance any different with the engine not running?
Check your manifold vacuum with a vacuum gauge...they aren't expensive.
Is your brake pedal spongy feeling, or do you just have to press real hard to stop. If your pedal is spongy feeling and goes all the way to the floor, you have air in your lines. Flush them and bleed them with fresh brake fluid.
If you just have to push real hard but not a spongy brake, then you probably aren't getting any boost. Is the brake feel/performance any different with the engine not running?
Check your manifold vacuum with a vacuum gauge...they aren't expensive.