The Stovebolt Site Forums The Parking Lot Big Bolts Suggestions for '46 1.5 T Dual Pot Master Cylinder???

Howdy All --- I've read through several brake threads but haven't found seen any specific recs for replacing the old single pot master with a dual pot power brake master. I know there are some underbody, frame mount aftermarket units avail but has anyone here installed one? Also I am considering using Randy's front adapters and 14" disks so I'm wondering what the main considerations are. Go with piston bore that matches original diameter & stroke or...?

Any thoughts or personal experience appreciated.

Corvette non-power MC come for F and R discs, no reference, that would be a start, just find something w/ similar setup.

Another couple of thoughts are late 70's early 80's C-30 I think they are 1 3/8" and one off of a bit later P-30 box van.

I'm going thru the same thought process right now with my '46 2 ton.

I am hoping to do a stock drum/drum rebuild and add a dual circuit master cylinder without any vacuum assist. I can't see why this won't work.

Puppy, the original was vacuum boosted so I can't see why it would work! Plenty of options for master cylinders out there.... Just need to fabricate the mounts and do the plumbing!

I do know that the original master had a 1-1/4" bore x 1-1/2" min. stroke. Seems to be a fairly high volume set-up, but then, the rear brakes one these 1.5's are ginormous. I'm wondering if there is a formula by which the total volume of fluid that needs to be moved can be determined. I'm just guessing, but I imagine that disk brakes don't require as much fluid movement. That would indicate that something close to the stock bore & stroke should be adequate.

Also, the original had Hydroboost which I will likely replace with modern parts as well. The new Cummins engine does have a power steering pump that I have been told is more than adequate to handle both steering & brakes. I'm shopping around for a complete master with boost that can be frame mounted but haven't settled on any particular setup yet. Here too, I am open to any experience/wisdom the group has to offer.

I converted my '54 GMC 2 Ton. We removed the original bracket for the M/C and made a new bracket(cuz I'm CHEAP) and used a Master Cylinder from a '78 Chevy one ton van. (1-1/4",same diameter as my original) It was a HydroBoost originally,but I felt it'd be much easier to skip the plumbing nightmare,so I installed the M/C without a brake booster. (For now-when I find a booster that is small enough to fit (8-9" diameter),but big enough to stop the loaded truck,I can install it fairly easily.)I also used the stock pushrod but left the retaining washer off,and added a short spacer in the pocket the pushrod seats in,but you may not have to do that. I just didn't want the pushrod to bind from the angle through its travel. Since I don't have front Disc brakes,I bought an adjustable proportioning valve on eBay and installed it in the front brake line. It bolted to the HydroVac bracket on the frame. I haven't finished adjusting it yet (bad fuel pump) but it's roughed in pretty close. It stops a little better than it did with the old system and a dead HydroVac,and has a much better feel to it,and a LOT more peace of mind. I found the easiest place to split the front and rear brakes was about even with the battery box,inside the frame rail;there's a "T" there where they split. I just removed the T,ran the rear brake line over from the Master Cylinder to the rear brake line,and ran the front line from the Master Cylinder over through the proportioning valve and into the line to the front brakes. I started with the adjustment at a little less than mid way on the P.V.,and intended to adjust it back and forth for the best feel and so both ends lock up about the same on a smooth gravel road,but my fuel pump took a break,so it's on hold until my replacement arrives. The way I routed the lines,when I find the booster I want to use,I'll make a plate the booster can mount to that will bolt to where the Master Cylinder mounts now,and the Master Cylinder can move back far enough to bolt to the booster,without opening any lines. I'll have to put a trap door over the M/C under the seat. I'm going to use a small breaker box door.)
A word to the masses-when you buy a rotary vane electric fuel pump on eBay,don't buy the $50.00 special-get a good one. I spent 2 days getting this thing properly installed,and it wouldn't do anything but make the power wire (the red one) hot and run my battery down. I figured it was just stuck,so I tapped on it all over wirh my smallest hammer,but it never turned a bit. Now waiting for word from the seller on whether he'll extend my 14 day warranty to two months,since I bought it a month and a half ago,but I've only had it on the truck for a day. If they won't exchange for a good one,I'll take it off and find out what went wrong and hopefully fix it.
Speed

Thanks Speed --- I'm still shopping for a master and hope to find a newer unit that will fit onto the frame without too much hassle and be easy to find parts for. Also have to rig the pedal. My bus came with a firewall mounted single pot master and I don't know if it was original or maybe a transplant that came along with the 350 motor. I've seen a few aftermarket units that come with everything including pedal but I'm guessing they are from China (ie; crap). The hunt continues and thanks to all for the input.

Since my new engine will be a diesel (Cummins 4BT), vacuum units are out. Diesels don't make vacuum and I don't trust the aftermarket vac pumps. That leaves Hydroboost as the best option. Looks like the larger Ford & Dodge diesel trucks might make good options. Later model pull outs are plentiful and they are fairly cheap & easy to rebuild.

Has anyone here tried installing one of these units?