Brake booster delete thoughts

[ZEROPILOT]

My KP 61 has a rock hard pedal due to a bad brake booster. A rebuilt booster is very hard to find and there is very limited room in there since I have a non standard engine.
Does anyone here run a brake booster delete plate? And can you recommend it? I don't mind a firm pedal. But i would like to be able to actually stop.

[davew7]

If you are going to delete the booster, you will have to change the pedal ratio on the brake pedal lever. Your current pedal pivot point give you a ratio around 3.5 to 1, and you will need a ratio for manual brakes between the ranges of 5 thru 7 to 1 ratio. Seeing how you prefer a firm pedal you will probably want something around the 5 to 1 range.
There is a couple things that require modification to convert to manual brakes. Once you have removed the booster you will have to fabricate a mounting plate for the M/C. You need to design the mounting plate with both the booster bolt pattern and the M/C pattern in the plate. But the plate needs to have the M/C pattern located as high as possible and still clear the top edge of the larger booster hole in the fire wall.
Next you will need to reposition the push rod clevis hole (higher) on the brake pedal lever. [location depending on ratio selected] You do not want the push rod angled more then 7* going into the M/C, [side loads the piston] so this may require relocating the M/C even higher on the fire wall. You might be able to use the stock push rod in the booster, but you will probably have to make a new push rod from a bolt that is the correct length. Just be very careful when grinding the hex head down to match the radius of the stock push rod. You do not want any binding of the rod / piston connection.
If you do take the booster apart, to use the push rod, note that it is "SPRING LOADED" .
DaveW7

[davew7]

One more item when switching a manual brakes. If your KP 61 does not have a lite return spring on the brake pedal lever, you should install a spring to assure that the piston in the M/C retracts completely. If not you could prevent the fluid from returning to the M/C and causing the brakes to drag. DaveW7

[ZEROPILOT]

Thank you. In looking back at old posts, I see that this has been as hotly contested issue.
Yesterday while disassembling my master and booster, I became aware that my front brake lines seem very restricted. I have new calipers, rubber lines and master. So I'm thinking that I either have a pinched steel line somewhere or a blocked line or the splitter block that goes to the right and left front brakes.
Since the system holds vacuum....for days....now I'm thinking my hard pedal and no brakes might be a flow issue.
What are your thoughts?

[davew7]

The splitter block, I assume is the brake bias valve Vs a Tee. Reading your other post, it sounds like there is a very good change you have rust in the system from setting, which cause the valve to jam. I would dis-assemble, clean, and flush the complete system to be on the safe side. DaveW7

[ZEROPILOT]

Thanks for that, Dave
I'm going to take the front lines apart and blow compressed air through them and see how it goes.
I'm just discouraged. It's been a long time and a lot of work for such little result.
Ed

[ZEROPILOT]

Is there an actual proportioning valve in that system? I couldn't google a photo. And would a malfunctioning one also give a hard pedal?
I scored a junked master with a lot of the original lines and junctions in it. So I have some spares now.

[davew7]

If you have a line restriction, it would cause the brake pedal to have slow travel. If the brake line and or system is blocked then it would be hard pedal. If the KP 61 has a pressure differential switch/ proportioning valve than it is possible that the internal piston could block either the front or rear braking system. You should be able to tell if just the front or rear system is working? By the same token you could have a caliper/wheel cylinder piston(s) jammed or rusted, which would cause a pressure un-balance condition, forcing the metering piston to one side which would mean only half the system is seeing brake pressure. DaveW7

[LittleRedSpirit]

If you have a disc rear end it should just be a splitter if you have a drum rear end its a pressure limiting device that has a needle valve and spring inside.

Pull it all apart, and clean the lines or replace them.

[Hen may possibly be a nut]

I don't think it has been mentioned that another way you can adjust the feel of your brake pedal is by changing the master cylinder diameter. Smaller MC gives a softer feeling pedal requiring longer stroke to stop. Larger MC the opposite. Generally you would need to go for a smaller MC if deleting the booster.

For full race cred you could also look into a twin master setup with a balance bar. And it'd improve your engine bay clearance even more. There are any number of kits available, or possibly someone has something off the shelf to suit KP61.

[Big T]

Pedal box. Will post a pic later. Added bonus of giving miles of room for trumpets. You will need a smaller master as Hen has noted. I'm running 5/8" fronts with 3/4" rear. The rear is slightly too large but I had a couple of that size spare. Hoping I can tune it out with the balance bar. Brakes are Brembo all round. 4 pot fronts 2x40mm and 2x46mm pistons. Rears are 2x40mm.
https://uploads.tapatalk-cdn.com/20181224/3f9e656b251cefae465ef5daa239d275.jpg

[ZEROPILOT]

I'm not sure what was wrong. But blowing out all the lines and junctions as well as the proportioning valve fixed it.
Now the only issue is a small one. The pedal play is almost 1". I've got to get my fat ass back under the dash and re adjust that brake pedal. I can stop now. The pedal travel is just too long.
How much free play should there be? I'm thinking 1/4"? Whatis that? 8mm?

[davew7]

The correct push rod clearance at the master cylinder is 1mm between the push rod and the M/C internal piston. That should give you about a 1/4 to 3/8" free travel at the pedal.
Note you MUST have clearance between the push rod and piston to allow brake fluid to return. Davew7