LS1 front brake upgrade master cylinder
- Thread starter LS1 BU
- Start date
I installed a different master over the weekend. After some research I picked a step bore master of of a 86 caprice. It has a 40mm and a 28mm piston. Now the pedal Is higher and vechile stops much better. Also holds the car better at the starting line when trying to load the convertor.
mattsmonte
New Member
- Joined
- Nov 7, 2008
So this 86 stepbore works with the OEM boost unit?
turbo96max
Member
- Joined
- Jun 6, 2007
great question, i have a similar issue. dont like how i bottom out the pedal. used a 85 monte set up. newmaster and used booster( dual diag). im thinking about a larger master. the biggest that will work actually....??? was this a stock 86 caprice unit?
unfortunately I know a vet member who has done this swap and would do an entire write up with parts #s but he isn't happy with the board so he refuses.
I know the feeling, I did a ps swap years ago and got grilled for it cus I'm not a vendor and at the time the big IC all cost $1000 bucks.
but the LS1 brake install its been done on a GN for sure. btw nice big drum brakes in the back I want to get those next!
I know the feeling, I did a ps swap years ago and got grilled for it cus I'm not a vendor and at the time the big IC all cost $1000 bucks.
but the LS1 brake install its been done on a GN for sure. btw nice big drum brakes in the back I want to get those next!
turbo96max
Member
- Joined
- Jun 6, 2007
is "step bore" mean anything special?? or can one just go to autozone and ask for a master for an 86 caprice and call it a day?
I had a 1980 original power boster and the caprice master would not fit it. I had to buy a power boster for a 86 cutlass. All the gn and t type boosters should work with the caprice master. On my stock 1980 booster the master cylinder piston bore would not fit into the hole on the booster. This master cylinder is about 1/2 the weight as the stocker and looks really cool. I'll try and get a pic for you.
turbofish38
Le Pétomane
- Joined
- Dec 3, 2002
The stock G-Body vacuum brake master cylinder is also a step bore. It's 36mm and 24mm. I've always used the smallest bore I could get away with. Capacity is not the issue. A smaller bore MC generates more line pressure than a larger one. In other words you should have had better pedal feel with the smaller MC so I'm guessing the real problem was in the master cylinder and not because it was too small.
I ran across this and thought it was pretty interesting. Scroll down to the tech tip. http://www.artmorrison.com/2006cat/51.pdf
I've read plenty about smaller bore master cylinder having more pressure. My stock master was a 25mm bore. This caprice one is 40mm and 28.6 step bore. The braking is 100% better. Night and day difference. I can also hold 200 more rpm at the starting line before pushing thru the brakes. I was told to use a stock master with my ls1 brakes up front and ford 9inch rear brakes.(Big drums) This was 100% wrong. The pedal was so low after installing the front ls1 brakes with the stock master. I bleed the system 5 times because I thought there was air. There wasn't. Stock master had a very low and mushy pedal. The LS1 calipers and big 9 inch wheel cylinders hold alot more fluid then the stock brake parts. The bigger master moves more fluid. I'll find the part number for the caprice step bore master. Best $60.00 I've ever spent on my car.
Did something similar, LS1 BU ..
I did the Global West front end with LS1 12" brakes up front, and Ford 9" in rear with disc brakes (that I believe came from an Explorer). The car handles much better than before, and except for slight wheel rub on full turns and large BS of front rims, the conversion would be excellent. Rear brakes don't hold lot of boost, though, and overall the braking has not really impressed me for what is there. I was told by GW that the stock PM would handle it, but not so sure now that I read this thread with your results. Pedal travel was not an issue. I have RedRegalT's vacuum brake kit to go on, but not sure of all that's in it as far as MC and so on. Any thoughts as to how to go once I get in there so I do it right first time?
PS Because of other issues with 9" rear end, specifically with the Detroit Locker, I will be putting stock 10 bolt with drums back in for a while.
I looked at RedRegalT's kit I was sent, MC is GM part #18010023, which corresponds to an '86 S-10 pickup MC. Looking at your NAPA MC online, it looks exactly like the one I was sent. So, I should be good to go once I get it in there. The kit has booster, MC, pedal, and pushrod, instructions, and it is all clean. Looks to be just what the doctor ordered.
I did the Global West front end with LS1 12" brakes up front, and Ford 9" in rear with disc brakes (that I believe came from an Explorer). The car handles much better than before, and except for slight wheel rub on full turns and large BS of front rims, the conversion would be excellent. Rear brakes don't hold lot of boost, though, and overall the braking has not really impressed me for what is there. I was told by GW that the stock PM would handle it, but not so sure now that I read this thread with your results. Pedal travel was not an issue. I have RedRegalT's vacuum brake kit to go on, but not sure of all that's in it as far as MC and so on. Any thoughts as to how to go once I get in there so I do it right first time?
PS Because of other issues with 9" rear end, specifically with the Detroit Locker, I will be putting stock 10 bolt with drums back in for a while.
I looked at RedRegalT's kit I was sent, MC is GM part #18010023, which corresponds to an '86 S-10 pickup MC. Looking at your NAPA MC online, it looks exactly like the one I was sent. So, I should be good to go once I get it in there. The kit has booster, MC, pedal, and pushrod, instructions, and it is all clean. Looks to be just what the doctor ordered.
