low vacuum, stick with power or switch to manual brakes???
03-11-2012, 01:48 PM
#1
2nd Gear Member
Thread Starter
Join Date: Mar 2006
Location: 03246
Posts: 477
low vacuum, stick with power or switch to manual brakes???
Well I bit the bullet today and removed the booster from the car. Removed the drivers seat and for all my procrastinating on this, it didn't come out too bad. It's an original 69 power brake disc/drum system, no power steering. I was sure I had a vacuum leak and after going through everything else it was clear that damn booster was fubar. Some solid advise is what I need at this stage. This engine only produces 8 inches of vacuum at idle. It is a 418W, the engine builder warned me running power brakes may be problematic. The booster had quite a bit of fluid in it. It was one of the only parts during the restore that I chose to reuse, bad decision lol. Should I try a Booster Dewey rebuild and see if the brakes will be right with such low vacuum? I'd hate to go that route, reassemble the thing and not have it work correctly. I know you like pics:
Under the circumstances it seems I would be wise to convert to a manual brake setup. I know I'll need a manual pedal and that the power pedal support will work with some effort. A 74 maverick master seems to be the popular choice and an adjustable master rod too. What happens with distribution block? What kind of changes to the lines at the block need to happen? Am I missing anything for the swap? Is it possible I'm overthinking this thing and that I should have the booster rebuilt and try it? Good weather is coming and I gotta move forward one way or the other. Thanks in advance.
Under the circumstances it seems I would be wise to convert to a manual brake setup. I know I'll need a manual pedal and that the power pedal support will work with some effort. A 74 maverick master seems to be the popular choice and an adjustable master rod too. What happens with distribution block? What kind of changes to the lines at the block need to happen? Am I missing anything for the swap? Is it possible I'm overthinking this thing and that I should have the booster rebuilt and try it? Good weather is coming and I gotta move forward one way or the other. Thanks in advance.
Last edited by chillininnh; 03-11-2012 at 04:02 PM.
03-11-2012, 02:26 PM
#2
6th Gear Member
Join Date: Aug 2007
Location: Elk Grove, CA
Posts: 5,896
There are a couple other options.
1) Swap to a set of Rhoads lifters. They collapse at lower rpm's to reduce duration and valve overlap, improving low-rpm vacuum (and torque). I run them in my 331 and I'm happy with the improved low-end response. They do clack a bit as a result of the lifters collapsing and smacking the valves into their seats, but I find it tolerable. These lifters were stock on Viper V10 motors for a long time.
2) Switch your vacuum advance line from ported vacuum to full manifold vacuum. This May require some slight timing and advance curve adjustments, but it will get you higher vacuum at idle. Performance tuners sometimes like to do this to have better control over timing advance.
I'd recommend rebuilding the booster and trying #2 first. It's the cheapest and easiest of your available options atm, although it may require some timing tweaks. I like option #1 as well, but that's a bit more in depth than you may want to go.
1) Swap to a set of Rhoads lifters. They collapse at lower rpm's to reduce duration and valve overlap, improving low-rpm vacuum (and torque). I run them in my 331 and I'm happy with the improved low-end response. They do clack a bit as a result of the lifters collapsing and smacking the valves into their seats, but I find it tolerable. These lifters were stock on Viper V10 motors for a long time.
2) Switch your vacuum advance line from ported vacuum to full manifold vacuum. This May require some slight timing and advance curve adjustments, but it will get you higher vacuum at idle. Performance tuners sometimes like to do this to have better control over timing advance.
I'd recommend rebuilding the booster and trying #2 first. It's the cheapest and easiest of your available options atm, although it may require some timing tweaks. I like option #1 as well, but that's a bit more in depth than you may want to go.
03-12-2012, 05:28 AM
#3
6th Gear Member
Join Date: May 2009
Location: PA
Posts: 5,232
There are a couple other options.
1) Swap to a set of Rhoads lifters. They collapse at lower rpm's to reduce duration and valve overlap, improving low-rpm vacuum (and torque). I run them in my 331 and I'm happy with the improved low-end response. They do clack a bit as a result of the lifters collapsing and smacking the valves into their seats, but I find it tolerable. These lifters were stock on Viper V10 motors for a long time.
2) Switch your vacuum advance line from ported vacuum to full manifold vacuum. This May require some slight timing and advance curve adjustments, but it will get you higher vacuum at idle. Performance tuners sometimes like to do this to have better control over timing advance.
I'd recommend rebuilding the booster and trying #2 first. It's the cheapest and easiest of your available options atm, although it may require some timing tweaks. I like option #1 as well, but that's a bit more in depth than you may want to go.
1) Swap to a set of Rhoads lifters. They collapse at lower rpm's to reduce duration and valve overlap, improving low-rpm vacuum (and torque). I run them in my 331 and I'm happy with the improved low-end response. They do clack a bit as a result of the lifters collapsing and smacking the valves into their seats, but I find it tolerable. These lifters were stock on Viper V10 motors for a long time.
2) Switch your vacuum advance line from ported vacuum to full manifold vacuum. This May require some slight timing and advance curve adjustments, but it will get you higher vacuum at idle. Performance tuners sometimes like to do this to have better control over timing advance.
I'd recommend rebuilding the booster and trying #2 first. It's the cheapest and easiest of your available options atm, although it may require some timing tweaks. I like option #1 as well, but that's a bit more in depth than you may want to go.
As for the valve noise some people complain about, it's less apparent than the normal sound from "solid" lifters, which I have in my 66.
03-12-2012, 08:14 AM
#4
2nd Gear Member
Thread Starter
Join Date: Mar 2006
Location: 03246
Posts: 477
Well I sent the booster off to Dewey for rebuild this morning. I'll adjust the timing, bump up the idle and tune for highest vacuum at idle and see what happens. If that doesn't do it I'll try a vacuum canister. If I'm still having trouble I guess there's a vacuum pump in my future. A set of Rhodes lifters may very well solve my problem but I just don't want to take the top end off the motor. The vacuum advance is locked out btw.
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