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4wheel discs, FOUND PERFECT MASTER CYLINDER!!

hmm. so i guess on my "stock" k5. mines soft bc of havnign another bad M/c possibly? i did go to 33's and am runnin extended stainless braided all theway around though..
 
*Update* - The one I installed before went bad and I went to O'Reilly to exchange it. Come to find out the one they gave me to start with was for a 2 wheel disc truck. I exchanged it for the 4 wheel disc model, which did in fact have the huge reservoir. After installing this MC I had better brakes, although I do have to push the pedal kinda hard. I believe this could be due to the vacuum booster not working as well against the larger MC. The correct model number was 10-2754
 
Well for those of you with older trucks, I figured out how to fit a newer master in my '78.

I used a booster from a '90 3/4 ton, and a master from a '99 1/2 ton with four wheel discs. If you take your old booster off, and grind the four rivets off the back that attach it to the booster bracket, then you can pull the bracket off your old booster, and it will slide right onto the four studs on the back of the new booster. That will allow you to bolt a newer booster to your old style firewall. The newer booster has the same stud pattern on the front as the old booster, as well as the back. So the only thing to look at is the bore on the front of the booster. The old one has a smaller hole, and won't allow the newer MC's to slide back into them properly. The push rods from the booster to the MC are the same though, old and new. The rod from the brake pedal to the booster is shorter on the new boosters though. I found wrench flats on my old rod, which I used to unscrew the tip. Then I cut the tip off the rod on the new booster. Slid the rod tip from the old one onto the new one, to lengthen it to the proper measurement. All in all, this is the best my brakes have ever been. Oh, and my old brake lines were two different sizes where they attach to the MC, and the new MC had the same size for each port. So I just had to get an adapter fitting for one of the lines, as it was 3/16 inverted flare and the old line was 1/4" inverted flare.


I've got some phone pics of the process if anyone is interested.
 
I'm not sure on the bore sizes, but I am running Eldorado calipers in the rear w/ parking brakes and Dana 60 standard front calipers. If it makes a difference I know mine takes the larger of the two brake pad options for the Dana 60. I think the two options are LB7 and LB9. Mine is the LB9. After running this MC for a while I have mixed feelings about it. Pedal travel is great as it takes up the slack quickly, but the pedal is very stiff since I haven't upgraded the booster. The more I drive it the better the brakes seem to get, but I replaced the MC at the same time I replaced the front axle with turned rotors and new pads. I think as the pads and rotors get worn in the brakes are getting better. The hood does occasionally rub the top of the reservoir very slightly, just enough to leave a streak of dirt on it.
 
Now that you mention the hood rubbing thing, I should tell you guys that the MC from the '99 1/2 ton with 4 wheel discs did not fit under my hood at all. Not even close, the reservoir is way too big. It's easy to fix though. Where the four studs on the back of the booster are, I just stuck three washer on each of the top two studs, to space the booster out at the top and tip it downward a bit. This lowered the MC plenty for the reservoir to clear the hood.
 
pvfjr said:
Now that you mention the hood rubbing thing, I should tell you guys that the MC from the '99 1/2 ton with 4 wheel discs did not fit under my hood at all. Not even close, the reservoir is way too big. It's easy to fix though. Where the four studs on the back of the booster are, I just stuck three washer on each of the top two studs, to space the booster out at the top and tip it downward a bit. This lowered the MC plenty for the reservoir to clear the hood.
Click to expand...

That seems like a simple fix. Were there any adverse affects to doing this? Did it affect the pedal setup? I also thought about finding a smaller reservoir to go on it since the hole spacing is probably pretty standard.
 
Oxyacetylene said:
That seems like a simple fix. Were there any adverse affects to doing this? Did it affect the pedal setup? I also thought about finding a smaller reservoir to go on it since the hole spacing is probably pretty standard.
Click to expand...
Nope, no ill effects whatsoever. You could probably get buy with just one washer. My hood was a good three inches from closing in the front, and three washers was plenty for me.
 
Good info guys I'm going to see if this will work on a Dodge. I have a 84 W350 Crew cab with D60's and rear disc using 3/4 ton Chevy calipers and rotors.
 
Awesome

I installed this last night on my 84' blazer. Bolted right up. I did had to take the reservoir off my old master cylinder and put it on the new one to clear the hood. I don't know when the last time my brake pedal was this firm.
 
My brakes still suck after a new 1 ton master. I took out the ride height brake adjuster also. All my dads trucks with 14 bolts have insane rear brakes and mine don't do anything. They haven't even worn the hatching of the new rotors yet.

I've bleed them a lot also
 
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