what are the differences inbetween the two?
is there actually a difference?
application: 87 F350 CCC SSB 4WD
is there actually a difference?
application: 87 F350 CCC SSB 4WD
Brake master cylinder: vacuum vs. hydroboost?
- Thread starter IDIoit
- Start date
idiabuse
Full Access Member
about 1000 psi difference at the calipers
sjwelds
Full Access Member
He's asking if there is any difference in the master cylinders themselves, not the booster method (vac or HB)
correct.
i have a bran new master cylinder from my vacuum brake booster, was wondering if it would work with the hydroboost system now installed.
not against getting another if need be.
just wondering if i can use the new one i have.
i have a bran new master cylinder from my vacuum brake booster, was wondering if it would work with the hydroboost system now installed.
not against getting another if need be.
just wondering if i can use the new one i have.
crash-harris
Breaker! Breaker!
IIRC there is no difference in bore or bolt spacing. Only one I've seen modified to fit was a factory 1/2 ton MC that a guy on FSB did his hydroboost swap with. He was keeping the factory 1/2 ton brakes and axles just swapped to hydroboost and didn't crack open any brake lines. The bolt spacing was the only difference. Someone with a trucks equipped from the factory with vacuum boost and another with factory hydroboost should verify though. I'm always skeptical about giving info when I haven't had first hand experience.
junk
Full Access Member
I also thought there was a minor spacing issue with the two bolts that fit the master to the booster. Like 5 minutes with a file will open the holes up enough for an F250/f350 master to fit the hydroboost unit.
If you use a F450/fsuperduty master there is a small hex plug / adapter on the rear brake outlet. On some trucks it has an actual valve in it and some trucks are straight through. My understanding is it has to do with Fsuperduty having rear disc and F150-F350 having rear drums. Some poeple have reported keeping this piece matched to the rear brakes seems to have benefit.
I went with the larger Fsuperduty master. More pressure and reservoir.
If you use a F450/fsuperduty master there is a small hex plug / adapter on the rear brake outlet. On some trucks it has an actual valve in it and some trucks are straight through. My understanding is it has to do with Fsuperduty having rear disc and F150-F350 having rear drums. Some poeple have reported keeping this piece matched to the rear brakes seems to have benefit.
I went with the larger Fsuperduty master. More pressure and reservoir.
icanfixall
Official GMM hand model
Most vacuum brakes came with a 1 1/8 bore master cylinder. Then Ford recognised the rear self adjuster issues with the low or sinking brake peddle so they "invented" the 1 1/4 inch bore mc. Still had issues but it was a mild fix for some. If you attempt to use the new 1 1/4 bore on the hydroboost you will need to open up the 2 mounting holes on the master cylinder body. Its aluminum and easy to do. You will need to remove lots and it will look like a firm foot on the peddle will blow it off the studs. Wont happen. You can ease yourself and use a couple of washers. Now what you end up with is still marginal brakes because you didn't upgrade to the 1 5/16 bore master cylinder. What the larger bore gives you is more VOLUME available of brake fluid in the brake lines. Of course you can't force more volume into a closed system but.. You have the ready capacity to fill the rear wheel cylinders that are usually out of adjustment so they require more fluid to operate...Now.... Lets the dogs loose on this.....
^ im with Gary.
thanks folks!
been workin on a 86 F250 all day
i will not modify a mastercylinder.
i have done this before with disastrous results.
will never do it again.
i will be purchasing the correct MC
now if i can get @lindstromjd to clue me in on what he got it from (the hydro unit)
i will be making a purchase
been workin on a 86 F250 all day
i will not modify a mastercylinder.
i have done this before with disastrous results.
will never do it again.
i will be purchasing the correct MC
now if i can get @lindstromjd to clue me in on what he got it from (the hydro unit)
i will be making a purchase
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lindstromjd
Black Sheep
thanks folks!
been workin on a 86 F250 all day
i will not modify a mastercylinder.
i have done this before with disastrous results.
will never do it again.
i will be purchasing the correct MC
now if i can get @lindstromjd to clue me in on what he got it from (the hydro unit)
i will be making a purchase
'94 or '95 F-Superduty with a 460. An old *** Cable truck with the PTO and boom/bucket.
that does not specify a bore size.
also is that the extra port someone was talking about? would be perfect for a brake switch!
I will let you do the math...but I will explain principle
2 mc
1.25
1.3125
Pi R Sq = Surface area
Surface area x 1000 lbs force from booster....1000 is an example number = psi
Thus the larger MC vs the smaller MC =
Larger has less psi however greater volume to fill wheel cylinders and calipers
Smaller has higher psi however lesser volume to fill wheel cylinders and calipers
It is very basic and easy to prove....
Just sayin
Personally I run the Hydroboost MC
JM7.3CW
2 mc
1.25
1.3125
Pi R Sq = Surface area
Surface area x 1000 lbs force from booster....1000 is an example number = psi
Thus the larger MC vs the smaller MC =
Larger has less psi however greater volume to fill wheel cylinders and calipers
Smaller has higher psi however lesser volume to fill wheel cylinders and calipers
It is very basic and easy to prove....
Just sayin
Personally I run the Hydroboost MC
JM7.3CW
it's correct.if you zoom in you can see the bore size on the unit in the pic.it's the one i bought for chip truck so i know first hand it's the one too.
the extra port you must be thinking of im guessing is on the power steering pump reservoir.
You must be registered for see images
the part number for that is: E5LY-3A697
but the last i remember they are no longer being made.you'll have to score a used one,T the return line,or make your own return tube in yours.
i bought mine here:
http://www.fordpartsgiant.com/parts/ford-reservoir-asy_e5ly-3a697-a.html
though since members claim they are discontinued.id call before placing my order to see if they actually have it.
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