Stabalizing Vacuum for Brake Booster

[Cupid 10]

Oops, that should have been stabilizing...

 

 

So, I put a decent cam in my 351C.

 

#7168

 

ENGINE: FORD 351W V8

RPM RANGE: 1500-6500

 

Duration at 0.006" Lift:Intake: 312?Exhaust: 322?Duration at 0.050" Lift:Intake: 234?Exhaust: 244?Lift at Cam:Intake: .325"Exhaust: .340"Lift at Valve:Intake: .562"Exhaust: .588"Timing at 0.050" lift:OpenCloseIntake:10? BTDC44? ABDCExhaust:59? BBDC5? ATDCCenterlines:Lobe Separation - 112?Intake Centerline - 107?

 

 

My braking is sporadic at low speeds. Most times I have decent vacuum to operate brakes (stock front discs), but when the car is at idle 800rpm-ish (let's say i'm coming to a stop sign and I push the clutch in), sometimes it's a different story. (I measured 12 in at idle with my vacuum gauge)

 

I'm looking for ideas (for example, vacuum canisters of some sort). Anybody have any?

 

I'm also going to upgrade to better brakes up front. Possibly throw some discs out back...(Because I can :biggrin:, and If I can, I should) Would love to get her on the track some day....I'm a chicken....I know it!:whistling:

Edited June 16, 2010 by Cupid
misspelled word

[Cupid 10]

Oops, that should have been stabilizing...

 

 

So, I put a decent cam in my 351C.

 

#7168

 

ENGINE: FORD 351W V8

RPM RANGE: 1500-6500

 

Duration at 0.006" Lift:Intake: 312?Exhaust: 322?Duration at 0.050" Lift:Intake: 234?Exhaust: 244?Lift at Cam:Intake: .325"Exhaust: .340"Lift at Valve:Intake: .562"Exhaust: .588"Timing at 0.050" lift:OpenCloseIntake:10? BTDC44? ABDCExhaust:59? BBDC5? ATDCCenterlines:Lobe Separation - 112?Intake Centerline - 107?

 

 

My braking is sporadic at low speeds. Most times I have decent vacuum to operate brakes (stock front discs), but when the car is at idle 800rpm-ish (let's say i'm coming to a stop sign and I push the clutch in), sometimes it's a different story. (I measured 12 in at idle with my vacuum gauge)

 

I'm looking for ideas (for example, vacuum canisters of some sort). Anybody have any?

 

I'm also going to upgrade to better brakes up front. Possibly throw some discs out back...(Because I can :biggrin:, and If I can, I should) Would love to get her on the track some day....I'm a chicken....I know it!:whistling:

Edited June 16, 2010 by Cupid
misspelled word

[ForceFed70 14]

Manual brakes maybe? I tried the vacum canister but didn't notice much of a benifit. Best option would be a vacum pump on a pressure switch, but it's costly...

 

You could turn the idle up...

[ForceFed70 14]

Manual brakes maybe? I tried the vacum canister but didn't notice much of a benifit. Best option would be a vacum pump on a pressure switch, but it's costly...

 

You could turn the idle up...

[69cobraman 10]

Cupid, maybe you could find one of those dual diaphram models. They supposed to help low vacuum.

[69cobraman 10]

Cupid, maybe you could find one of those dual diaphram models. They supposed to help low vacuum.

[foothilltom 33]

I may have this all backwards, but I thought vacuum decreases quickly as the throttle opens. If this is true, increasing the idle would actually decrease vacuum and hamper the booster even more?

 

The highest vacuum should be with a closed throttle and higher RPMs (like getting off the gas at reasonably high RPMs with clutch disengaged). If this is true (and I'm wrong constantly), I would think your best braking pattern would be when you stay off the clutch until the very last second and downshift through braking.

 

At idle, you're pretty much stuck with whatever vacuum your setup makes, but increasing the idle seems like the wrong approach.

 

I'm over my head, but thought I'd contribute my requisite $.02.

 

Tom

[foothilltom 33]

I may have this all backwards, but I thought vacuum decreases quickly as the throttle opens. If this is true, increasing the idle would actually decrease vacuum and hamper the booster even more?

 

The highest vacuum should be with a closed throttle and higher RPMs (like getting off the gas at reasonably high RPMs with clutch disengaged). If this is true (and I'm wrong constantly), I would think your best braking pattern would be when you stay off the clutch until the very last second and downshift through braking.

 

At idle, you're pretty much stuck with whatever vacuum your setup makes, but increasing the idle seems like the wrong approach.

 

I'm over my head, but thought I'd contribute my requisite $.02.

 

Tom

[Max Power 74]

I may have this all backwards, but I thought vacuum decreases quickly as the throttle opens. If this is true, increasing the idle would actually decrease vacuum and hamper the booster even more?

 

 

Vacuum decreases as the throttle opens quickly, but regains in short order. Vacuum can increase on cams with a lot of valve overlap by increasing the rpms without load, so yes, bumping up the idle can increase vacuum on cars with aggressive cams.

 

I would be interested in a solution as well, as my cam has about 10 of vacuum at idle in gear, and the idle is already bumping into the main enrichment circuits.

[Max Power 74]

I may have this all backwards, but I thought vacuum decreases quickly as the throttle opens. If this is true, increasing the idle would actually decrease vacuum and hamper the booster even more?

 

 

Vacuum decreases as the throttle opens quickly, but regains in short order. Vacuum can increase on cams with a lot of valve overlap by increasing the rpms without load, so yes, bumping up the idle can increase vacuum on cars with aggressive cams.

 

I would be interested in a solution as well, as my cam has about 10 of vacuum at idle in gear, and the idle is already bumping into the main enrichment circuits.

[Cupid 10]

I'm with you on increasing idle rpms. You have it exactly right on the downshifting. I downshift through the gears to brake efficiently. Well, that is, until I moved to the Washington, D.C. area. A lot of the times i'm in bumper-to-bumper traffic. That's where I have the slight problems. I just maintain at least 1-2 cars distance to allow for braking, but you have the idiot drivers that are either A) gawking at my Mustang, or B) changing lanes in front of me as if I have anti lock brakes, thus causing unsafe conditions for everybody.

 

Btw, i'm not overly concerned with gawkers as they give me thumbs up, wave, blow their horns, and just smile...I may even get a "rock on man!" every now and then.

[Cupid 10]

I'm with you on increasing idle rpms. You have it exactly right on the downshifting. I downshift through the gears to brake efficiently. Well, that is, until I moved to the Washington, D.C. area. A lot of the times i'm in bumper-to-bumper traffic. That's where I have the slight problems. I just maintain at least 1-2 cars distance to allow for braking, but you have the idiot drivers that are either A) gawking at my Mustang, or B) changing lanes in front of me as if I have anti lock brakes, thus causing unsafe conditions for everybody.

 

Btw, i'm not overly concerned with gawkers as they give me thumbs up, wave, blow their horns, and just smile...I may even get a "rock on man!" every now and then.

[Grabber70Mach 107]

Washington, D.C. area

 

What part of the area?

[Grabber70Mach 107]

Washington, D.C. area

 

What part of the area?

[Cupid 10]

Landover, MD

[Cupid 10]

Landover, MD

[Grabber70Mach 107]

I work right up by Landover. I work off Central avenue at the large Postal facility on Edgeworth drive. But live about 30 miles away in Southern Maryland, have a friend down here that has a mustang yard with lots of parts if your looking for anything or just want to check it out one day.

[Grabber70Mach 107]

I work right up by Landover. I work off Central avenue at the large Postal facility on Edgeworth drive. But live about 30 miles away in Southern Maryland, have a friend down here that has a mustang yard with lots of parts if your looking for anything or just want to check it out one day.

[Cupid 10]

Don't threaten me with a good time! I'd love to go check it out. I'm actually building a house off central,(church). Send me his info please. Love to meet you one day.

 

Tim

[Cupid 10]

Don't threaten me with a good time! I'd love to go check it out. I'm actually building a house off central,(church). Send me his info please. Love to meet you one day.

 

Tim