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Old 05-17-2009, 12:51 PM   #17
Chuck78
Registered User
 
Join Date: Apr 2005
Location: Columbus, OH
Posts: 197
Re: Power Brake Booster Adapter Bracket

Capt, I sent you a PM yesterday, but I noticed today in my sent messages that it was not there... I hate it when that happens.

I started working on a booster bracket for my 62 so that I can fit a hydraulic clutch in the stock clutch master cylinder location 2.5" to the pass. side of the brake pedal pushrod. I was going to use some random steel that I have laying around to extend the $5 brackets that I bought with the Pirate Jack's 8" dual diaphragm booster, but then I just decided to take a used 89 suburban booster and chop the bracket off of it and graft them together.
I've got it tacked together, but it was 4AM and the neighbors probably don't appreciate a lightning show as I don't like to weld in my cluttered garage. I made it 4-5/8" long, no offset on the angle at all. The clutch master I'll be using is, like I said, a $32 1962 auto trans truck single reservoir brake maser (removing the residual valve), and it requires clearancing the firewall mounting flange of the booster bracket, so I made it so the bracket extended upwards more on the firewall so I'd have an upper bolt location above the clutch master mount, which has the diagonal 2 bolt pattern vs horizontal (or vertical like the $65 Wilwood master of the same physical size).

If you made up a set of brackets like this, and decided on a standard booster to use with them (or even make the brackets slotted like the ones I bought to chop and extend), you could then figure on a pushrod length and fab up that.
The astrovan/safari 85-87/89? boosters are a good looking 9" dual diaphragm booster with a little longer pushrod, and have the short master cyl pushrod for newer masters and most disc/drum masters past the early 70's. The 68 or so 9" truck dual diaphragm booster (look up 68-70 C30/3500 trucks, some burbs and pickups also) is also a great bet, and has the longer master cylinder pushrod for the older masters that still used the deep bore like on a manual brake truck. If doing 4 wheel drums, one would most likely need this type of booster so they can put a deep bore drum brake master on, and also, 71-72 trucks had deep bore masters as well and front discs/rear drums, so this $120 or so booster would be good for both applications as long as you were okay running a master that was only made for 2 years or so on a disc/drum application. The parts stores still can get these no problem. If you switch later, you can always stuff a rag in the booster's master recess, and chop the pushrod off shorter and grind the end down to a nice round. Some boosters have a pushrod that just sits in there in a socket and you can pull it out.

I got the pirate jack's "MBM" brand (aftermarket repro manufacturer) booster because it had a 3/8x24tpi threaded pedal pushrod, and I thought this would be easier to make work, as it's a standard but not so common thread, and bicycle axles on rear coaster brake wheels come in hardened steel 3/8x24tpi, so I thought with some of the rod couplers Pirate Jack';s sells, and maybe one of their pedal rod extensions, I could make that work easily.

I took the manual brake pushrod off mu truck, and although the pin that goes intot he master is slightly tapered, I tapped a 3/8X24 tpi thread on it, but turns out I didn't have enough diameter until about halfway back on the taper to get good thread depth, so the 1-1/8" rod couplers wouldn't thread on far enough to get to the good threads, and I didn't want to chop up my original parts to mod them for this use. So I used their $14 truck pedal rod extension that's a 5" long solid sleeve with 1.6" of female threads on each end, and a heim joint for the pedal pivot with 1-1/2" of male threads on the end of it. re-tapped a longer 3/8x16 rod coupler to 24tpi, threaded onto heim joint all the way, leaving 1/2" left to thread a bicycle axle in. Since the threads were somewhat questionable due to the nature, I'm drilling a hole on the flat on the hex coupler, right at the butt of the two threaded pieces, and plug welding all three together there.

Now for what I would have really done, after doing it... The Pirate Jack's booster takes a slightly narrower master than I realized, so I had to either oversize or elongate my master's bolt holes to fit onto the 3/16" or so narrower bolt pattern. That on top of spending $19 on pushrod parts ($14 on heim joint with long rod coupler, $5 on axle), I think now I would just be inclined to do the following.
My 89 suburban booster pedal pushrod is a thick 1/2" of 5/8 shaft with a big flat that mounts similar to the 62 pedal with a large shoulder bolt with a smaller 3/8 thread. Hole needs drilled slightly larger in this piece, but works. This is about 4" long, and has I think a female 3x8 x 16 thread on it, and then the booster pushrod comes out the same size up to the firewall before it reduces to 5/16 with a ball and socket on the end inside the booster, and attaches to the pedal section of the rod where it has a male 3x8x16 thread. I'd snag this pedal piece, and then use some cold rolled steel bar stock about 1/2" and cut a nice square end on it, and then take a long hardened steel 3/8" hex head bolt and weld the head to the end of the rod, and thread into the 89 suburban booster piece, so that you could have a washer and jamb nut on it for a little adjustment. On the other end at the booster, pushrod has again the flattened out flange for a thru-bolt or clevis pin that looks like it attached to the pedal there, and on the older truck unit, to the pivot linkage. On this end, I would determine the length with bracket and all, and grind two flats on the sides of the end of the rod, and weld two flat pieces of steel to the sides to make the outside portion of the clevis piece, and drill it out and get a clevis pin and cotter from Lowe's.

Also, if you were worried about reducing the pushrod down from 1/2"+ to 3/8 at the end of the booster piece, you could use 1/2" "all thread" threaded rod instead of cold rolled steel round bar stock, and put a 1/2" rod coupler in the middle of that with a jamb nut on either end.

this is the 89 suburban booster that I had laying around, you can see the booster side of the pushrod, and the other piece threads onto it and goes to the pedal. This is also the booster bracket that I had to chop up and graft to the other booster bracket to make one long one. I'm sure Capt Fab could make something much slicker looking with some flat steel plate!

Oh, the pedal pushrods on our trucks are a 7/16 thread, I think 7/16x24 tpi, so it is possible to reuse the same pedal attachment piece if you could find a die or some threaded rod that size. I don;t think I remember seeing that size in my tap & die set.

Food for thought, let me know if anyone else has any ideas or questions, or if you want anymore advice, capt!

The pushrod centers of the stock master are 2.5" apart, and the new clutch master will fit in the stock firewall hole with new mounting holes drilled (theres even an indentation in the firewall there on mine?), but since you are just routing a pushrod through the brake hole in the firewall instead of a large master cylinder bore register piece, you can slide the booster slightly towards the fender before drilling the firewall for the booster bracket, and this gives you a slight bit more clearance if using the $32 1962-3 single res. brake master for clutch. If using the $65 Wilwood master of the same physical size, the bolts are vertical instead of diagonal, so this probably isn't necessary. If changing the angle and not using a heim joint at the pedal, you'd have to then stick a few flat washers under the shoulder bolt at the pedal attachment, or maybe it could move to the other side of hte pedal arm to re-align.

a few S10's used a 9" dual diaphragm booster also, as well as I think 77-80 or 77-81 vettes (different pedal pushrod connection), and many other GM vehicles. I recommend the dual diaphragm for clearance reasons if you have a big block or GMC V6, and also for more stopping power. Keep it simple for the Capt, by sticking with one or two boosters to fab the stuff up for.

Good luck anyone who tries this, and Capt, if you want to try and make these, and need more info from me, let me know. bracket should be about 4-5/8" or so, but if moving the booster 5/8" towards the fender, you could really shrink it down to almost 4" with the particular clutch master and booster I'm using (not the ones I recommended above, need to check the fit of those).
__________________
Chuck in Ohio
*1962 GMC 1000 Panel Truck - 305D/Saginaw 4sp soon: 351C V6 + AX15 5sp OD trans, & 75-87/91 disc brake front end
*1988 Suzuki Samurai 4x4 project, VW 1.9L mTDI, Toyota R151F transmission & Toyota full floater axles, LWB body tub stretch project
*Many 1977-1979 Suzuki GS motorcycles, Kawasaki KDX220R, '77 Suzuki PE250, etc
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