Brake Boosters
Thread Starter
Race Director
Joined: Dec 1999
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From: Forked River NJ
Brake Boosters
There is the stock C3 vacuum canister, big and works fair for performance driving. There is Hydroboost which I have right now. It's reaction time is very strange and gives strange pedal feed back. Could be withthe LS3 pump the pressures are not exactly right. What other brake booster options are people running. I have heard the C6 booster works very well. Anything else out there?
Tech Contributor
Joined: Jun 2004
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From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
A couple years back I bought a used C6 booster in order to see if I could pull some weight off the car. The C6 booster looks a lot like the C3 booster, but it only ended up being about 3 or 4 ounces lighter (not worth all the time and effort to swap it in). I expect that a C6 booster should function just fine in other vehicles, as I've never heard any complaints from C6 owners.
I eventually used an '84 C4 booster on my car. It was half the weight (4# vs 8#) of a C3 booster, and the smaller diameter (compared to later C4 boosters) made it fit well. I'm using a C5 m/c with it, and the brakes are darn firm. Very happy with this combo, performance wise, and weight wise (about 10-11 pounds lighter).
Not everyone's cup of tea, but it worked out well for me.
I eventually used an '84 C4 booster on my car. It was half the weight (4# vs 8#) of a C3 booster, and the smaller diameter (compared to later C4 boosters) made it fit well. I'm using a C5 m/c with it, and the brakes are darn firm. Very happy with this combo, performance wise, and weight wise (about 10-11 pounds lighter).
Not everyone's cup of tea, but it worked out well for me.
Le Mans Master
Joined: Apr 2007
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From: Graceland in a Not Correctly Restored Stingray
...I eventually used an '84 C4 booster on my car. It was half the weight (4# vs 8#) of a C3 booster, and the smaller diameter (compared to later C4 boosters) made it fit well. I'm using a C5 m/c with it, and the brakes are darn firm. Very happy with this combo, performance wise, and weight wise (about 10-11 pounds lighter).
Not everyone's cup of tea, but it worked out well for me.
Not everyone's cup of tea, but it worked out well for me.
Tech Contributor
Joined: Jun 2004
Posts: 20,905
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From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
), and I've got enough idle speed advance timing to get decent vacuum for the booster.The C4 conversion was pretty easy. I shortened and threaded the (pedal) pushrod for a clevis to hook to the C3 pedal. I then made a small aluminum adapter to connect the 4-hole firewall to the 2-stud booster. Then it was just a matter of removing about 1/16" of material to oval out the C5/C6 m/c retaining holes to match the C4 booster stud centerlines (why Chevrolet does crap like this that's close, but not the same, aggravates me), and also a slight length adjustment of the booster pushrod that goes into the m/c.
I'll confess again that I'm not familiar with the details of the manual brake conversion.
Thread Starter
Race Director
Joined: Dec 1999
Posts: 19,610
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From: Forked River NJ
I figure I'll have to do some mods to any booster I use. The LS 3 has a somewhat aggressive cam but should provide plenty of vacuum for brakes. I have to get back to this car and finish it up.
Le Mans Master
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I'll confess I don't recall what the vacuum reading was. The engine is reasonably well behaved (as I've aged I've gradually moved from the heavy car/uncivilized engine combo to the lightweight car/smoother engine combo ), and I've got enough idle speed advance timing to get decent vacuum for the booster.
The C4 conversion was pretty easy. I shortened and threaded the (pedal) pushrod for a clevis to hook to the C3 pedal. I then made a small aluminum adapter to connect the 4-hole firewall to the 2-stud booster. Then it was just a matter of removing about 1/16" of material to oval out the C5/C6 m/c retaining holes to match the C4 booster stud centerlines (why Chevrolet does crap like this that's close, but not the same, aggravates me), and also a slight length adjustment of the booster pushrod that goes into the m/c.
I'll confess again that I'm not familiar with the details of the manual brake conversion.
), and I've got enough idle speed advance timing to get decent vacuum for the booster.The C4 conversion was pretty easy. I shortened and threaded the (pedal) pushrod for a clevis to hook to the C3 pedal. I then made a small aluminum adapter to connect the 4-hole firewall to the 2-stud booster. Then it was just a matter of removing about 1/16" of material to oval out the C5/C6 m/c retaining holes to match the C4 booster stud centerlines (why Chevrolet does crap like this that's close, but not the same, aggravates me), and also a slight length adjustment of the booster pushrod that goes into the m/c.
I'll confess again that I'm not familiar with the details of the manual brake conversion.
Tech Contributor
Joined: Jun 2004
Posts: 20,905
Likes: 962
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
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Le Mans Master
Joined: May 2006
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From: League City Tx
On my 404" LS, when it had a 226/238* 115 LSA cam, my brakes worked great...just as good as stock..(C5Z)
When I went to the 239/252* 115 LSA cam, it only had 8-9hg of vacuum at idle in gear and the brakes were terrible. I even took it to a dealer to have the whole system flushed/bled/cycled the ABS module etc thinking it was a brake problem... Brakes sucked. Then I put the vacuum gauge on the motor and saw the crap vacuum.
On another LS car of mine, I had a 237/242* on a 113 LSA and the brakes worked fine.
Just throwing it out there. I think I would investigate the hydroboost issue and fix that before going back to vacuum.
Thread Starter
Race Director
Joined: Dec 1999
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From: Forked River NJ
I'm not sure what you consider aggressive but...
On my 404" LS, when it had a 226/238* 115 LSA cam, my brakes worked great...just as good as stock..(C5Z)
When I went to the 239/252* 115 LSA cam, it only had 8-9hg of vacuum at idle in gear and the brakes were terrible. I even took it to a dealer to have the whole system flushed/bled/cycled the ABS module etc thinking it was a brake problem... Brakes sucked. Then I put the vacuum gauge on the motor and saw the crap vacuum.
On another LS car of mine, I had a 237/242* on a 113 LSA and the brakes worked fine.
Just throwing it out there. I think I would investigate the hydroboost issue and fix that before going back to vacuum.
On my 404" LS, when it had a 226/238* 115 LSA cam, my brakes worked great...just as good as stock..(C5Z)
When I went to the 239/252* 115 LSA cam, it only had 8-9hg of vacuum at idle in gear and the brakes were terrible. I even took it to a dealer to have the whole system flushed/bled/cycled the ABS module etc thinking it was a brake problem... Brakes sucked. Then I put the vacuum gauge on the motor and saw the crap vacuum.
On another LS car of mine, I had a 237/242* on a 113 LSA and the brakes worked fine.
Just throwing it out there. I think I would investigate the hydroboost issue and fix that before going back to vacuum.
Drifting
Joined: Jul 2008
Posts: 1,483
Likes: 459
From: Lititz PA
Thanks for all the replies. I'll try raising the front end up high and cycling the rack back and forth several times.
If that doesn't work, I think I read somewhere there is a brake booster that is smaller in diameter, but has twin diaphragms. I was hoping that one of the forum members has already done this. I am really tired of the constant whine from the hydro boost.
Thanks again,
John
If that doesn't work, I think I read somewhere there is a brake booster that is smaller in diameter, but has twin diaphragms. I was hoping that one of the forum members has already done this. I am really tired of the constant whine from the hydro boost.
Thanks again,
John