Technical Bubbles or lack there of

I’ll check. What should it be?

 

I was tempted by these but didn’t use them. Good info for the future.

 

I was told my MC was bi-braketual, that it would go either way. Thanks for the picture, I now know what to look for.

 

Good stuff! Thank you. I will check this out.

 

I will be checking the push rod length. I haven’t driven the truck yet but there is enough braking that I can’t turn the wheels by hand but that doesn’t mean much I don’t think. I originally bled the brakes with the brake pedal and had what seemed like reasonable flow.

 

Thanks for everyone’s comments. I do appreciate the H.A.M.B. braintrust. I changed my avatar to the all go and no whoa truck. I just recently fired it up after having the initial break-in done on a dyno with a carb. Switched to a FI Tech system and it fired almost immediately and a few small idle air control adjustments had it running good. I’m very anxious to get my brakes figured out so I can drive this thing.

 

If there is no booster, about 6:1.

 

Regarding #1, I have the 1/4” free play. As for #2, instead of .020-.030” clearance I have .149” interference so I need to screw the pin in .169” to get .020” clearance. So, could the lack of clearance between the booster pin and the bullet in the master cylinder cause my soft pedal? I have some brakes but can push the pedal to the floor. Also, I haven’t made the adjustment to the pin yet.


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My pedal ratio is 5.33 with booster.


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That should be fine.

 

You won't get a proper bleed if the master cylinder piston does not fully return. For that, it requires free play.

 

If the master cylinder can't return to its absolute released position with 0 preload by the pedal or booster it does not recharge with fluid for the next stroke properly. Push the pedal down and release it with the cover off of the master cylinder and you should see a " geyser " of sorts squirt up in each reservoir...protect your paint unless it's all urethane or another bulletproof paint!.....beautiful truck Bro!

 

Gimpy beat me to it!....thr " geyser confirms what Gimpy said if all there is correct

 

Regarding your .149 clearance you need to screw the pin OUT toward the master not IN. Be sure to lock the pin with the jamb nut so it can't move on it's own.

 

I don't recall seeing where you bench bled the master, maybe I missed it!! They have to be bled off the car to get full stroke of the piston, bleeding on the car doesn't always allow the foll stroke. Ralphie

 

Yes, it was bench bled.


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What I believe is happening and what I’m trying to describe is I think the pin is out to the point the master cylinder never returns all the way so not only is there no clearance between the booster pin and the MC bullet it’s holding the MC open by .149. I screwed the pin in to see how much I could get and it was only .050. Am I thinking backwards? Wouldn’t be the first time.


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He said 0.149 interference, not clearance.

 

My bad, yes I see interference not clearance, need new glasses.

 

I’ve shortened the bullet that slides in to the MC by what I believe is the appropriate amount. So, if my yardsticks, rulers, verniers, depth gauges and arithmetic are correct I have .022 clearance. I’ll put it back together and see what happens.
Thanks to everyone for their advice.


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Any luck?

 

No change. I’ll bleed them again to see if the increased stroke changes anything.


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The amount of travel / throw / plunge on the master has been mentioned already. My math says that 4" of pedal travel to the floor and a 5.33 pedal ratio isn't giving and inch of travel at the master. About an inch or maybe a bit more (depending on the master) is what's required, as already mentioned. Whilst this amount of travel isn't necessary in normal service it can be necessary when bleeding the brakes.

You can lose a ton of this travel if the pedal position isn't correct - if it's already over center the effective pedal ratio will be reduced and throw lost. Visualise as a pendulum, there is more horizontal throw between say 5 o'clock and 7 o'clock than say 6 o'clock and 8 o'clock, even though the pivot has moved through the same 10 (time!) minutes = 30 degrees.

Chris

 

That all sounds reasonable but if the brakes were pressure bled is it applicable? If the air were really out of the system from pressure bleeding I would think I should have a good pedal within 2” of movement or so.

 

Wow, this is making me rethink rear discs. It shouldn't be the problem but there seems to be some miss match somewhere in your system. Please keep us up to date...thanks

 

A 4 wheel disc brake system will always have a softer peddle then a disc / drum set up.

A lot of cars from the 80’s and 90’s when 4 wheel disc first became popular had shit peddle feel but stopped fine

 

Do they pump up if they do is the pedal soft?

 

You can fix these by making a nylon insert that is a snug fit in the bore, and has the same ID as the brake line.

 

They don’t pump up at all. I can push it to the floor.

 

I’ve been rethinking the rear discs, too lately! I knew I didn’t need them, I just wanted them. I’ve talked to Wilwood and they say my 1” Corvette MC is fine with the calipers I have. I’ll keep messing with it.