master cylinder replacment questin n bore size

[sweetk30]

so I am looking to replace the master on my k30 plow truck .

I have hydroboost since k30 . also has the older style metal/cast master . this dam thing wont ever stop oozing out the top seal area for the cap .

so I was looking at the specs .

85 k30 5.7
bore - 1.3125 or 1" 5/16
1/2"-20 / 9/16"-18 threads .
disc front and drum rear.

looking at the newer master aluminum body plastic reservoir that don't leak .

96 c3500hd 5lug/10lug trucks .
bore - 1.5748 or 1" 9/16 just over that fraction
9/16"-18 / 1/2"-20 threads.
disc front AND rear.

only other option for newer master but little smaller bore.

92 c3500 8 lug
bore 1.250 or 1" 1/4
1/2"-20 / 9/16"-18
disc front and drum rear

so my question is : any real draw backs to the little bigger bore master ?

and worst case have to add in n adjustable prop valve to restrict rear over power with stock drum brakes 13"x3.5" shoe.

 

[diesel4me]

I think all hydroboost masters with the bail clip style covers leak--both the originals on my 2 diesel trucks did,and now the replacement master is starting to ooze fluid out of the cover now too--it stayed dry a few months,then it started weeping..beginning to think the hydroboost somehow pressurizes the master and makes the fluid come out of the gasket seal..the nature of the beast?..

The replacement master I put on my 3/4 ton 82 was the same part number that most GM full sized cars used in the 70's to 80's until they went with aluminum ones with the plastic fluid canister...it has 13" rear brakes,stops good,has a nice firm pedal,no excess travel in it...I think the bore size on it is about 1",I'll try to find the specs on it..

 

[diesel4me]

The master that is correct for my truck has a 1-1/4" bore...

I think the one you listed for the '92 C3500 would work OK...I'm no expert but I'm pretty sure a larger bore will move more volume,so more pedal effort is required...not sure if you'd notice it as much with hydroboost...

 

[Blazooki]

must read this if you never have:

http://www.pirate4x4.com/tech/billavista/Brakes/