Hydro boost power brake booster

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Alex Waddell

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I am putting a 3F-E in my 68 FJ40 with front disk brakes & drum rear brakes.
The 3F-E intake manifold gets pretty close to the brake master cylinder so I am considering using a Hydro boost power brake booster which is smaller.
Does anyone have experience with using a Hydro boost in their 40? If so, do you have a recommended maker & model number?
 
cruisermatt

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They are all generally the same Chevy/Ford/Dodge other then how the pushrods attach to the original application pedals. I have found Chevy boosters to have the easiest pushrod to mod for use in a Toyota, they are long enough to cut the eyelet off and run a M10 die over to use your Toyota clevis.

Get the smallest master cylinder you can find if you are using FJ40/60 discs, anything over 1.125” bore is going to have zero pedal feel (super hard pedal with minimal travel) with a hydroboost
 
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Alex Waddell

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They are all generally the same Chevy/Ford/Dodge other then how the pushrods attach to the original application pedals. I have found Chevy boosters to have the easiest pushrod to mod for use in a Toyota, they are long enough to cut the eyelet off and run a M10 die over to use your Toyota clevis.

Get the smallest master cylinder you can find if you are using FJ40/60 discs, anything over 1.125” bore is going to have zero pedal feel (super hard pedal with minimal travel) with a hydroboost
I hear that the Chevy 2500 & 3500 trucks have Hydroboost. Are there any other Chevy models?
I hear that post 1996 Cobras & Mustangs as well as Dodge & Ford diesel trucks are hydro boosted too but may be harder to adapt.
 
cruisermatt

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I hear that the Chevy 2500 & 3500 trucks have Hydroboost. Are there any other Chevy models?
I hear that post 1996 Cobras & Mustangs as well as Dodge & Ford diesel trucks are hydro boosted too but may be harder to adapt.

Yes. Any GM that had a hydrobooster from 1975ish and up
“They are all generally the same Chevy/Ford/Dodge other then how the pushrods attach to the original application pedals. I have found Chevy boosters to have the easiest pushrod to mod for use in a Toyota, they are long enough to cut the eyelet off and run a M10 die over to use your Toyota clevis.”
 
derail

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Chevy and GMC astrovans are also hydroboost. That's where I picked mine up from. Also did what cruisermatt was explaining with cutting the eyelet off. This was for my c10, but it's all the same. Brakes have never been better.
 
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Alex Waddell

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Chevy and GMC astrovans are also hydroboost. That's where I picked mine up from. Also did what cruisermatt was explaining with cutting the eyelet off. This was for my c10, but it's all the same. Brakes have never been better.
Thanks for the input and it's good to know that I am going in the right direction. And I will definitely be taking your and cruisermatt's advice.
 
Hobbs81

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Many (maybe all) Suburbans, Yukons and Tahoes (regular 1500s) had them after about 2005. (I have a couple for sale if interested PM me). FYI, you do have power steering correct? I'm not sure that vintage PS pumps would have enough volume/pressure to run another accessory. I'm not saying they don't I'm just saying I don't know.
 
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Alex Waddell

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Many (maybe all) Suburbans, Yukons and Tahoes (regular 1500s) had them after about 2005. (I have a couple for sale if interested PM me). FYI, you do have power steering correct? I'm not sure that vintage PS pumps would have enough volume/pressure to run another accessory. I'm not saying they don't I'm just saying I don't know.
Yes I did an FJ60 disk brake conversion on a late 70's front axle tube. And I am putting in a 3F-E in as well so I have a newer power steering pump. But I don't know what the pressure & flow specs of the pump are. But I am taking the chance that it will be OK. I just PM'd you.
 
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Yes I did an FJ60 disk brake conversion on a late 70's front axle tube. And I am putting in a 3F-E in as well so I have a newer power steering pump. But I don't know what the pressure & flow specs of the pump are. But I am taking the chance that it will be OK. I just PM'd you.

What size tire? front locker? I think the 3FE pump will be fine with 33" and a 40 (lighter weight overall then a 60). If it isn't it is very easy to bolt a Saginaw in place of the 3FE pump later
 
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Disclaimer: make modifications to your own comfort level with them. I’m not an expert, I’ve done a moderate amount of research and encourage you to do your own. The following information is intended to let you know what is possible, not explain all the steps to do it.

Pressure and flow can be modified on Saginaw pumps. Flow can be increased drilling the high pressure output fitting out to 5/32” (I’ve not done it yet). Pressure can be increased by removing shim washers from the “slug” behind that fitting. After selecting the shortest one of three I had and also removing the two shim washers. After assembly, I can palm steer my 40 on dry pavement at idle (with 33x10.50s).

Alternatively, a longer “slug” or adding shim washers would reduce pump pressure and should improve road feel.

The OEM Hydro-boost Saginaw pumps have extra fittings for a second low pressure return line.

The rebuilt 1980 Chevy 3/4 ton pump, with no housing, I bought appears to be setup for good pressure and volume. So far, it’s not installed, so I can’t be 100% certain. It should be a Saginaw P pump with 1375 psi and decent volume.
 
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Alex Waddell

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What size tire? front locker? I think the 3FE pump will be fine with 33" and a 40 (lighter weight overall then a 60). If it isn't it is very easy to bolt a Saginaw in place of the 3FE pump later
You are recommending a Saginaw pump and not a gearbox, right? If so, could you please recommend a model or the vehicle it came in?
And yes, I will be using 33" tires.
I went by an auto parts store and measured up a GM hydroboost and I believe it will fit if I mount it upside down.
Also, I looking at buying a reman unit for a 1995 Suburban since it had front disks and rear drums.
I am tempted to buy the master cylinder for that model too so I know it fits and works right but I don't know if that matters.
The cylinder bore is 1.125" which may be on the large side for my rig. Do you have any other suggestions?
I also found a hydroboost reservoir for a reasonable price on Ebay that I hope is acceptable. hydroboost power steering tank w/#12 outlet | eBay - https://www.ebay.com/itm/124773639189.
Since I will be using a master cylinder made for disk front and drum rear, do you think that I still need the master cylinder check valves or are they built in.
I already bought them as well as a proportioning valve so I suppose I will still use them.
 
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Alex Waddell

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Disclaimer: make modifications to your own comfort level with them. I’m not an expert, I’ve done a moderate amount of research and encourage you to do your own. The following information is intended to let you know what is possible, not explain all the steps to do it.

Pressure and flow can be modified on Saginaw pumps. Flow can be increased drilling the high pressure output fitting out to 5/32” (I’ve not done it yet). Pressure can be increased by removing shim washers from the “slug” behind that fitting. After selecting the shortest one of three I had and also removing the two shim washers. After assembly, I can palm steer my 40 on dry pavement at idle (with 33x10.50s).

Alternatively, a longer “slug” or adding shim washers would reduce pump pressure and should improve road feel.

The OEM Hydro-boost Saginaw pumps have extra fittings for a second low pressure return line.

The rebuilt 1980 Chevy 3/4 ton pump, with no housing, I bought appears to be setup for good pressure and volume. So far, it’s not installed, so I can’t be 100% certain. It should be a Saginaw P pump with 1375 psi and decent volume.
I suppose that I should have read your post before I commented on crusermatt's post since you had a lot more information on the Saginaw pump.

My 3F-E manual only states a minimum pressure of 1067 psi at idle and does not specify the normal running pressure or the flow rate.

I will probably try to use the 3F-E pump and see if it works.

But having two return lines does sound easier than having to mount an external reservoir.

Please send links for your research on the Saginaw pump.

What kind of modifications did you need to do to mount the pump? However it may be different for the 3F-E.
 
Hobbs81

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Saginaw pumps can be upgraded to support hydroboost. I did it when I installed hydroboost on my CJ. Keep the housing (reservoir) and replace the pump itself. I don't recall exactly how to do it but it wasn't difficult. Or expensive.
 
cruisermatt

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You are recommending a Saginaw pump and not a gearbox, right?

Right, that is if the 3FE pump struggles or goes out on you one day (they’re getting hard to find). I think it will work fine though.

As for the master cylinder yes you will need a 10lb residual valve for your rear drums if you are still running the original FJ40 rear brakes. Otherwise the rears brake lines will never hold pressure. Wilwood sells in-line universal ones.

I think 1.125 is going to be way too big. That is what I am running with my 5th gen 4runner front brakes and 80 rear discs and the pedal is very firm. Try to find something like 7/8 or 15/16”. Hydroboost is going to firm things up big time so you want to use a much smaller MC then you normally would to get good pedal feel. Just my experience
 

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