master cylinder help

[springer]

Can anyone tell me what M/C they used on a K5 with a rear disc swap. I have been looking at alot of them 79trans-am, firebird,1ton's. the problem is that the bolt pattern will bolt up to my booster, but the round part (bore) that fits into the booster is smaller on the ones that i just mentioned. I am assuming that this matters. If anyone out there has run into this what M/C did ya use. It seems to me that some people used the ones above, but i dont know how because of the bore size.My K5 is an 86.Please help this is driving me crazy

 

[dremu]

Can anyone tell me what M/C they used on a K5 with a rear disc swap. I have been looking at alot of them 79trans-am, firebird,1ton's. the problem is that the bolt pattern will bolt up to my booster, but the round part (bore) that fits into the booster is smaller on the ones that i just mentioned. I am assuming that this matters. If anyone out there has run into this what M/C did ya use. It seems to me that some people used the ones above, but i dont know how because of the bore size.My K5 is an 86.Please help this is driving me crazy

The bore size varies... we'll presume as a K5 your truck has vacuum boost (unless it's diesel?) ... and what year is it?

Also, have you tried your stock master? On my K5 I'm running rear disc with the stock booster, combo valve, etc and it works just fine. Other people have reported the same ... others still have problems, but that may be due to the master being old, etc.

-- A

 

[springer]

It's an 86. I have a new M/C on there right now but it's just a stocker. I also did new lines, braided flex hose to the calipers, and I'm using adjustable P-valve not the stock one. I dont have hydroboost I just have standard power brakes.

 

[dremu]

It's an 86. I have a new M/C on there right now but it's just a stocker. I also did new lines, braided flex hose to the calipers, and I'm using adjustable P-valve not the stock one. I dont have hydroboost I just have standard power brakes.

Well, the big question is ... are you having problems? Were you before you put in the adjustable valve? Did you bypass or modify the stock one, or is it still plumbed as before?

-- A

 

[springer]

the stock p-valve is gone it's not even on the blazer anymore. I had perfect brakes before i did the rear disc ever since they have been shi**y. They do work I just have excessive pedal travel. I've been reading up on this and it is a common thing, but everybody says they just use a 1ton or trans-am or corvette M/C. I cant find one that fits to the booster. They must be changing that also. My stock M/C has a big round part that goes into the booster and the other ones have a much smaller part that goes into the booster. I dont know if this matters or not. It seams to me that the bore size isnt the important thing, It has to be the valving thats inside the bore.

 

[Mudstud]

I use PN 101534 (77 K30 4x4 1 5/16” bore) and have great brakes on my 76K5. Fronts are plumbed directly from MC- no prop valve. Rear has adj prop valve. Bleeding is the real trick. I made a pressure bleeder out of the low pressure garden sprayer and custom cover to bleed my brakes. It works well.

 

[dyeager535]

I'd try bleeding more. My dad did disks in his k20, stock everything else, brakes are decent if not fine (didn't spend a lot of time driving it, but they do work and pedal travel isn't excessive) but it did take a bit of bleeding.

 

[BGKYK5]

If bleeding isn't the problem, you will want to go to a larger bore M/C to reduce pedal travel. The larger bore moves the same amount of fluid with a shorter stroke.