My hydraulic clutch and Hydroboost setup

[Yukon Jack]

Been seeing some posts the last couple days about hydroboost so I thought I would do a detailed post about the install of a hydroboost system and hydraulic clutch from a donor 1989 Chevy 1 ton (old body style) on to my 1969 Chevy K20.

I really like the hydroboost brake system but, of course, I was used to manual brakes so any assist was welcome.

The hydraulic clutch is also nice. I would have had a major problem using the stock z-bar setup with the headers and the swapped in bbc.

When I started contemplating this project, member MikeC mentioned that it might be wise to reinforce the firewall due to the weight of the hydroboost and fact that I was adding the hydraulic clutch. I had a buddy cut me this reinforcement for my firewall with his plasma cutter.



I have a template of this reinforcement that also has the location of the various holes that were needed. Let me know if a copy of this template is needed by anyone. I have to mail it so I would need your mailing address.

Another buddy made me the metal shim you see that positions the hydraulic cylinder correctly so the push rod will attach to the clutch pedal.



The 1989 old body style 1 ton hydraulic clutch master is angled requiring the shim. I later found out that the new body style hydraulic clutch master would not have required that shim. Regarding the shim for the hydraulic clutch cylinder, the way I have it made, it attaches right next to the hydroboost bracket. The template is angled so the bottom is 5/8" thick and the top of the shim angles down to 1/16" thick. The shim is 2 5/8" wide x 2 5/8" tall.

I got the cylinder mounted on the firewall, threaded the push rod and am using a 5/16" threaded clevis rod end to attach the rod to the clutch pedal. Cycles freely and the rod will push in as far as needed. Might have to make a stop to limit the clutch pedal.



I am using the 1989's engine and bellhousing so the slave cylinder was already attached to the bellhousing.

Next I got the hydroboost brake cylinder hung on the firewall. I had to knock the two lower stud bolts off the pedal assembly and drill a couple holes but no biggie. Because of how this is mounted, I have to modify how the steering column attaches to the firewall as the brake booster bracket covers one of the attachment holes.



Mounted the rod to the brake pedal same as with the clutch. The brake booster rod is 3/8" while the hydraulic clutch rod is 5/16". I cut off the end of the brake booster push rod, threaded it and got it connected to the brake pedal using another clevis rod end.



I did have to have the high pressure line modified. I took the 1989 1 ton's high pressure line along with the stock high pressure line and had them combined - this allowed the metric end to be at the hydroboost master cylinder and they flare end to fit the stock steering box.

Here are some finished pics.

[jeffspower]

Great info. It's going to make that truck soo much nicer to drive. One note of caution: that multi- hole pin in your brake clevis, if any of the holes are "inside" the clevis, it could snap easily if you have to stomp on the brakes. Or even years of wear could snap it.

[Yukon Jack]

Thanks for the tip Jeffspower. I will definitely check the pin.

I will get the template copied for those who ask for it. I have to mail it so I would need your mailing address.

[onetonk5]

is there one particular hydroboost unit that fits our firewalls better than others?
your work looks great

[Yukon Jack]

This one fits very well, all I really had to change was knock two of the studs out of it, drill two new holes, use bolts in place of the two studs I took out and modify the push rod. Have to see if anyone chimes in with info on something that actually bolts in place with no mods.

[shifty]

Cool stuff, I never thought to drill that high because I thought that was too high up . Can you please do me a favor and shoot a picture from your driver side door area showing the interior hole for the hydraulic cylinder and the linkage for the pedal? I am curious:

- how high up on the pedal the cylinder post is mounted
- what the hole looks like and its location
- how straight the cylinder post is

All of these things will help me figure out what i'm doing

[beater69]

Yukons template is very cool, he mailed me one a couple of months ago.
The brake linkage rod that was on my hydroboost was about 1/2" to short. The brake pedal side fit the factory(69) hardware it was just to short. So I cut the rod in half, threaded both sides and added a coupler nut and two jam nuts and I was on my way. the down side was I threaded it to 7/16 diameter so I wasn't able to just go the hardware store to get the coupler nut, I had to go to a fastener store but otherwise no big deal.
I got my Hydroboost out of a 82gmc 1/2t 2wd diesel
I picked up the whole truck for $200, it was converted to a gas sbc, th400
I also used the front crossmember/discbrakes and rear end.
the thing drove 50 miles to my brothers place too.

[meathead95]

i got my template today. thanks yukon jack. i was wondering is your reinforcement plate aluminum? how did you attach it? i think pop rivets shoud be just fine, do you?

[Yukon Jack]

Mine is aluminum as my buddy had some lying around. I used some countersunk phillips head machine screws. I would think pop rivets would be fine as the master cylinder also secures the plate to the firewall. It probably wouldn't need anything other than the master cylinder bolts now that I think about it.

[Yukon Jack]

Good thing you bumped it - cause I forgot to get go out and get you some pics. I will try to do that in the next couple evenings.

Here is an old pic I found that shows the position very well.



This pic is from before I switched to the threaded rod end clevis.

[shifty]

That looks like it hits in a great place. Musta been a real booger to drill the pedal up that high

Can you tell me approximately how much rod travel you have? Do you happen to know, off-hand, how thick the firewall metal is in that spot? It looks really thick in the picture you posted, but I can't tell if I'm seeing the firewall metal and the metal from the plate you got over it

I really prefer that spot more than where I was gonna drill. Looks like it's back to the drawing board for my clutch bracket *sigh*

If you can eventually post anything else, that would be really cool.

[Yukon Jack]

The majority of the thickness you are seeing there is the aluminum plate. It is probably twice as thick as the firewall metal.

Thankfully I had the pedal assembly out when it was time to drill it, I'm not sure I could have drilled it with the pedal assembly installed under the dash, unless I had one of those 90 degree drill fittings. Pretty tight confines under the dash as you know.

See the rubber dust cover on the clutch rod - see where the black material is on the rod to the left of the rubber dust cover - I have black electrical tape around the rod at that location. From the left edge of the tape to the end of the hydraulic clutch master is the total amount of travel that was necessary - it can't be more than about 1 1/2".

Because of the ribbing on the interior side of the firewall and the way the rod needed to attach to the pedal to get the necessary travel without binding, I'm not sure there is any other location where the clutch master could have been positioned.

[shifty]

Travel sounds good. Master cylinder in F-Body (98-02 Camaro/FB/TA) requires 15/16" actual travel, so 1½" is actually excessive for me. This can be adjusted by using a bump stop or by welding a custom tab/joggle onto the pedal to make the connection farther up.

Thanks for the info, you don't realize what a huge help this has been for me. I was looking at this matter waaaay too hard. I will need to mull over this for a little while at home and look at fabbing up a new cardboard template for my setup.