350 Brake Booster - Ford Bronco Forum
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post #1 of 7 (permalink) Old 01-09-2017, 03:48 PM Thread Starter
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350 Brake Booster

Just finished upgrading my 89' brake booster and master cylinder to the F350 setup. Everything went smoothly. I've searched, but come up with different opinions about optimum vacuum to make this larger booster perform at its best. At warm idle right now my gauge on the booster vac line is reading 18 in-Hg. Will this suffice? Engine is 351W, all stock except for headers and all smog removed. Thanks in advance for the responses!
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post #2 of 7 (permalink) Old 01-10-2017, 11:35 AM
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That should be enough, my "fresh" 300 doesn't make more than 20 in/hg. 18 is a pretty healthy engine.

94 Bronco XLT. Beefy 351, 6" , 37's, 4.88: burnt
85 Bronco custom, 4" 37's, locked 4.56, 300 i6 4 bbl, np435/208
96 f350 XL, rclb, 351, c6, BW4407 xfer
78 f150 Ranger, 351m, t18, np205, rusty
90 f150, 95 f250, 96 f350 psd: stolen, sold, and burnt, respectively.
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post #3 of 7 (permalink) Old 01-10-2017, 05:01 PM
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unless you have a big cam or somethin, shouldnt have any issue. its not like the F350 351 engines are any different than Bronco 351 engines. you probably wont see any gains in the F350 master cylinder unless you put in bigger brakes however


-----96 5.0 E4OD--------------88 5.8 C6--------------96 5.8 E4OD------
---------KIA-------------------Mud/Trail---------------Daily Driver------
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post #4 of 7 (permalink) Old 01-10-2017, 05:07 PM
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Yo
Agree with Big Blue.
You have good vacuum and fit in the range according to Brake, Power, Hydro-Boost Booster, by Ford in a 96
VACUUM CHECK
Disconnect vacuum booster hose from booster.
Connect Rotunda Vacuum/Pressure Tester 164-R0253 or Rotunda Vacuum Tester 014-R1054 or equivalent to the vacuum hose with a T-fitting.
Key on, engine running. Allow engine to reach normal operating temperature.
Record the vacuum pressure.
Is the vacuum reading 57-70 kPa (17-21 in-Hg)?
Yes GO to N2.
No TUNE UP or REPAIR engine as required.

N2 SYSTEM INSPECTION
Key off.
Reconnect the vacuum line.
Inspect power brake booster check valve, rubber grommet and all vacuum plumbing for cracks, holes, bad connections or missing clamps.
Push down on brake pedal and hold.
Key on, engine running.
Does the brake pedal move downward when the engine is started?
Yes Vacuum system is OK.
No GO to N3 for diesel engines. GO to N4 for gas engines.

N4 COMPONENT ISOLATION CHECK
Key off.
Reconnect the vacuum gauge to the same point as in Step N1, but leave the rest of the system connected.
Key on, engine running at idle until vacuum reaches 57-70 kPa (17-21 in-Hg).
Key off.
Observe vacuum gauge for 1 minute.
Does vacuum pressure drop more than 1 in-Hg?
Yes DISCONNECT each component one at a time and REPEAT the test procedures in N4 until the leaking component is found. PLUG the disconnected vacuum line while performing the test procedures. REPAIR or REPLACE as required. On diesel engines with dash-mounted power brake booster, REPLACE power brake booster check valve also.
No GO to N5.

N5 BOOSTER LEAK CHECK
Key on.
Run engine until vacuum pressure reaches 57-70 kPa (17-21 in-Hg).
Key off.
Push down on the brake pedal and hold for a few seconds and release.
Does the vacuum drop to 0 kPa (0 in-Hg)?
Yes REPLACE power brake booster. No System checks OK. REMOVE vacuum gauge and RECONNECT all vacuum lines.


"...Use "Hard (Heavy Duty)" vacuum line for booster. Regular rubber hose such as used for WS washer fluid line will likely collapse after about say, 20 years. Inspect for any sign of kinking or collapse. Check vacuum draw available with a gauge connected between engine and booster. At idle, healthy engines draw somewhere between 17 and 22 in Hg. Check vacuum by depressing brake pedal firmly until it stops. The gauge should read a drop to approximately 10 in. Hg and then quickly recover to a normal reading. If vacuum takes too long to recover, there is a restriction in the volume, i.e.: fitting clogged or vacuum hose collapsed. Repair as necessary. While a defective booster will cause a hard pedal, a spongy or low pedal requires a hydraulic system check..." by Cardone

See my partially recovered Bronco web site ...Will need to clean up dead links & add many more new links some day. Thanks to Mr. Schwim!
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post #5 of 7 (permalink) Old 01-10-2017, 08:19 PM Thread Starter
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Thanks guys...learning as I go!
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post #6 of 7 (permalink) Old 01-10-2017, 09:11 PM
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I have an 96 f350, with a 351 and yes, other than smog stuff, it's the same as was in my 94 Bronco. The only difference would be a camshaft, and the variance would be minute considering it would be a factory cam

94 Bronco XLT. Beefy 351, 6" , 37's, 4.88: burnt
85 Bronco custom, 4" 37's, locked 4.56, 300 i6 4 bbl, np435/208
96 f350 XL, rclb, 351, c6, BW4407 xfer
78 f150 Ranger, 351m, t18, np205, rusty
90 f150, 95 f250, 96 f350 psd: stolen, sold, and burnt, respectively.
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post #7 of 7 (permalink) Old 01-11-2017, 12:16 AM
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Quote:
Originally Posted by Kingfish999 View Post
you probably wont see any gains in the F350 master cylinder unless you put in bigger brakes however
This is mostly true. I machined ("machined" ...slow and careful with a Dremel) my stock master cylinder mounting holes just wide enough to fit correctly on the F350 booster. It made a big difference without having to change calipers or wheel cylinders.
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