Bigger Vacuum vs Hydroboost

To improve braking, is it better to swap out an F150 vacuum booster for one in an F350, or just change it altogether for a hydro-boost system?

The F250/350 master cylinders won’t fit on a F150 booster. Going to a larger bore master cylinder will also require MORE pedal effort and make your brakes feel worse. To improve braking, you need a more forceful booster. The larger master cylinder bores are needed on the heavier trucks because the wheel cylinder volumes are larger, and require more fluid to enter for proper braking. You can use a large bore master cylinder on a lighter truck (I have a F450 hydroboost master on my F150), just expect that you will have a more firm pedal with less travel. If you convert to hydroboost with F450 components, you will have to use at least a F250 master cylinder since the F150 stud spacing is different. I used all F450 components from a junkyard, and the braking performance is drastically better than any vacuum system I’ve owned.

Thanks. I changed the title of my original post to read bigger vacuum vs hydro boost, because that's what I was referring to, and am still figuring this stuff out, including the right questions to ask.

Anyway... I saw on a forum someone swapped their F150 vacuum booster for an F350 vacuum booster and swore by the improved braking. He said it was/is a straight swap, which is appealing to minimize down-time. Down the rabbit hole I went, came across a video of someone swapping  the vacuum boost for a hydro-boost, and I've seen on this site people espousing the benefits of a hydro system. So I am wondering which way to go.

Which hydro system do you guys use?

I'm going the same way Jonathan went - F450.  That's 'cause Jim/ArdWrknTrk parted out an F450 and I got many of the parts, including the hydroboost stuff.

Sorry I misunderstood your post. The F350 booster is smaller diameter and deeper. I believe I read it has dual diaphragms inside, and is a more forceful booster... to apply more force on the larger bore master cylinder. You cannot fit a F150 master cylinder on a F350 booster, at least in the 80-86 cast iron style. So you would need the booster, the correct vacuum pedal, master cylinder, and the brake lines to the pressure differential valve which are different on the F350 master cylinder. Same amount of work as hydroboost except for the pressure lines and return to the steering pump. I would expect there to be some improvement with the F350 stuff since it is designed to stop more weight, but I bet it is chicken scratch compared to the hydroboost upgrade.

Thanks for clarifying. So how do both of these systems feel under foot? I keep reading they’re “better”, “definitely more power”, “amazing compared to old...” but what does it actually feel like? Do you just tap on the brakes and the next thing you know the steering wheel is between your teeth? Or is it still soft enough with a little play until the brakes grab (if you know what I mean)?

I cannot speak to what F350 system in a F150 would feel like since I have not done it. But my experience with vacuum boosted brakes in these older trucks is that they don’t stop well. You really have to stand on them hard to get aggressive braking. This was true in all of the vacuum boosted Bullnose trucks that I’ve owned, 1981 F150, 1981 F250 and 1986 F350 crew cab. When I put hydroboost in my ‘81 F150 the pedal became firm, but required very little effort to result in aggressive braking. You do not have to press hard at all. However, it has very little travel, and is not “soft”. They feel great to me. They are not grabby, it does not throw you through the windshield. If you stomp on them yeah, they lock up, but it’s not a hair trigger or touchy thing in my experience. There is plenty of control, and the firm pedal that stays high feels reassuring to me. Others may not like it. I admit it did take a little getting used to, and you have to retrain your muscle memory for braking, but I feel so much better about my ability to stop in traffic or while towing. The brakes are more effective on that old heavy truck than any other vehicle I have.

Vic Roma wrote

To improve braking, is it better to swap out...?

The stock brakes work fine when they're maintained properly.  Changing the booster is a band-aid; and an expen$ive, difficult one.  It would be much ea$ier to just fix the underlying problem(s).  The captions in this photo album explain most of them, and how to fix them:



Ignore the ones that don't apply to your truck.

BTW
That link will open a BIG webpage with a lot of pics, so I recommend you NOT click it on a phone - use a real computer with a fullsize monitor.