Then you know this one isn't supposed to work on non hydro systems then.
CK5
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ORU's 4 wdb master cylinder upgrade for our trucks
- Thread starter camiswelding
- Start date
Then you know this one isn't supposed to work on non hydro systems then.
Desert Rat
Fetch the comfy chair
The ORU one is only for hydroboost setups? I went to the site and it just says that it is an upgrade.
ORU's master is for hydroboost trucks only....
cam
If you go to www.napaautoparts.com and check out a few listing you will see that all the hycros even for the same year are different part number. I'm under the impression that the bore size is different between hydro and non hydro.
I'm not an expert on the subject by any means. You might want to call them and ask them. The site says that it's an upgrade for hydro systems right?
Add additional stopping power to your Hydro Boost equipped Suburban or Pickup without converting to 4 wheel disc brakes with the addtion of ORU's Ultimate Master Cylinder.
- GM 4 Wheel Disc Brake Master Cylinder with Hydro Boost
Desert Rat
Fetch the comfy chair
You are right, I totally missed the hydro boost part. Damn, what about us regular master cylinder guys? We get no love...
vac brakes suck 
Yep, convert to hydroboost. Means some re-plumbing but it's well worth it -- basically swap in the hydrobooster/master, the other brake pedal, and then new hoses between the booster and the pump and box.
-- A
How "required" is the pedal swap to match the hydro master?
Eric M.
1/2 ton status
It wasn't required with my 91 V2500 Burb. I think there were some other mods. I did to avoid having to change the pedal. I didn't have the pedal and I think the mods were simpler than changing the pedal.
Damn, wish I could remember what I needed to do .... maybe fabricate a bracket ....
I'll look under the dash and see if it jogs my memory.
Eric M.
The hinge point for the plunger rod is in a different place.
Your pedal may have the hole already; my '74 didn't, but I've heard that some (later?) do.
If not, you have to pull the pedal assembly out, take the brake one off and drill it, then reassemble, by which point it's just as easy to swap, assuming you have a donor.
At the very least you have to know WHERE to drill it, which means you have to measure a donor or get somebody in CK5 land to measure theirs. =))
-- A
oldtoyboyd
1/2 ton status
I am running a new p30 hydro master on my 91 v3500 with better pedal and no complaints for over a year now.I will have to look for the number of it but I think I got it for around 125.
Eric M.
1/2 ton status
did some digging around on napa's website.
85k30 stock master bore is 1 5/16" or 1.31" or 33.3375mm.
looked at a few years for p30 masters and all about the same but i checked a 96 p30 step van as i have one i work on alot at work.
so i looked threw the choices on the p30 masters for 96 p30 step van found this .
disk/drum with 13"x3.5" drums in rear 1 5/16 or 1.31" or 33.3375mm. ts-101982 napa #
disk/disk 1.33858" or 34mm. ts-101668 napa #
disk/disk 40mm bore for motor home. ts-102754 napa #
the stock masters are cast iron for our stuff. and the first 2 listed are cast iron. but the big 40mm bore listed is the newer style aluminum/plastic style. thay all have american threads on the listings .
i think i might just try the big 40 mm master with my build. and the rear disk i plan to run 3/4 ton calipers not 1/2 ton calipers. little bigger piston size on the 3/4 and same basic prices for both .
85k30 stock master bore is 1 5/16" or 1.31" or 33.3375mm.
looked at a few years for p30 masters and all about the same but i checked a 96 p30 step van as i have one i work on alot at work.
so i looked threw the choices on the p30 masters for 96 p30 step van found this .
disk/drum with 13"x3.5" drums in rear 1 5/16 or 1.31" or 33.3375mm. ts-101982 napa #
disk/disk 1.33858" or 34mm. ts-101668 napa #
disk/disk 40mm bore for motor home. ts-102754 napa #
the stock masters are cast iron for our stuff. and the first 2 listed are cast iron. but the big 40mm bore listed is the newer style aluminum/plastic style. thay all have american threads on the listings .
i think i might just try the big 40 mm master with my build. and the rear disk i plan to run 3/4 ton calipers not 1/2 ton calipers. little bigger piston size on the 3/4 and same basic prices for both .
Good info. I may see if I can dig up one of the 40mm ones as well. Are those all for hydroboost?
The 95 p30 van is a 40mm too if I remember correctly. They have it for a 4WDB system in a non hydro.
I think I was led down the wrong road when I read that you could not change to plastic resevoir from a cast one. I was told by a tech they do it all the time. He wanted 269 bucks for his version.
so i finally got this in and it works pretty good. i can still lock up the back tires before the front but i really have to try. the pedal is really really firm and doesnt whoosh like the stock stuff. i went 14 bolt with disc a few months ago and i think thats why my stock one went out. it was totally different afterwards.
so my current running gear is 1/2 ton front calipers on the ten bolt front, then 3/4 calipers on the 14 bolt. all stock hardlines and prop valve and i have stainless braided soft lines.
im not exactly sure what model this came from but was told it was the p30 master and booster. installed but never driven on in a k10. in my 85 the lines were backwards but everything bolted up.
so far im impressed with the difference and more positive feel to the brake pedal. its really firm now with only a 2 maybe 2.5 inch stroke. to lock em up i gotta really mash it. when i try to lock the rears up its about 75% of the time.
I pick up the 102754 and as most people have figured out it will not clear the hood of a 91.
