1978 k30 Brake lines

[DBear]

Hey there, redoing a 78 k30 crew cab. Years ago, I stripped the frame bare, and now have no brake lines. Looking for some pre-bent lines for the front main lines and front to back inside the frame rails. I've been finding some for 3/4 ton but not 1 ton. Is it possible that the 3/4 and 1 ton are the same? Just not sure how similar the 2 frames are? Any leads or advice would be appreciated. Thanks in advance

[wildwilly4x4]

Lines will be the same from 1/2 ton to 1 ton (except for that goofy load valve that 1 tons had at the rear...which needs to be deleted anyways)

[DBear]

Originally Posted by wildwilly4x4

Lines will be the same from 1/2 ton to 1 ton (except for that goofy load valve that 1 tons had at the rear...which needs to be deleted anyways)

I talked to inline tube and told me their 3/4 ton stuff wouldn't work for me. So, what you're saying is all the hard brake lines up front of the frame that 1/2 ton 4x4 stuff will work on my 1 ton 4x4?

[DBear]

Originally Posted by wildwilly4x4

Lines will be the same from 1/2 ton to 1 ton (except for that goofy load valve that 1 tons had at the rear...which needs to be deleted anyways)

https://www.inlinetube.com/products/sctb7343

[DBear]

Originally Posted by wildwilly4x4

Lines will be the same from 1/2 ton to 1 ton (except for that goofy load valve that 1 tons had at the rear...which needs to be deleted anyways)

Do you have a picture of the load valve that is not needed? Could you also tell me what it did and why it is not needed? Inline tube and other sites have 1/2 and 3/4 ton pre-formed lines, and you said they will fit the 1 ton 4x4 correct? Thank you for your help sir.

[Keith Seymore]

Originally Posted by DBear

Do you have a picture of the load valve that is not needed? Could you also tell me what it did and why it is not needed? Inline tube and other sites have 1/2 and 3/4 ton pre-formed lines, and you said they will fit the 1 ton 4x4 correct? Thank you for your help sir.

That height sensing valve was a Rube Goldberg-esque attempt at a mechanical anti lock brake system, before there was an electronic version.

It was specifically added to help meet MVSS Federal standards for stopping distance. Some test scenarios (combinations sorted by model, brake series, wheelbase, rear axle, tire type and curb vs GVW) were so tenuous that we would ask for a specific driver to run the test. We would run multiple tests and classify them as "development" until we got a pass and then categorize that one as "validation" and submit it to the Federal Government.

If you are not trying to meet federal stopping distance requirements by a within few inches then you could probably leave it off completely or, as suggested above, add a manual adjusting prop valve back there.

K

[DBear]

Originally Posted by Keith Seymore

That height sensing valve was a Rube Goldberg-esque attempt at a mechanical anti lock brake system, before there was an electronic version.

It was specifically added to help meet MVSS Federal standards for stopping distance. Some test scenarios (combinations sorted by model, brake series, wheelbase, rear axle, tire type and curb vs GVW) were so tenuous that we would ask for a specific driver to run the test. We would run multiple tests and classify them as "development" until we got a pass and then categorize that one as "validation" and submit it to the Federal Government.

If you are not trying to meet federal stopping distance requirements by a within few inches then you could probably leave it off completely or, as suggested above, add a manual adjusting prop valve back there.

K

Good info...I think I cut that off years ago when I starting stripping the frame down...i.e. the reason I am looking for pre-bent brake lines LOL.

Another member stated that I could use 1/2 or 3/4 ton pre-bent lines on my 1 ton 4x4, which he's definitely smarter than I on this situation. Have you seen that done before?

[Keith Seymore]

Originally Posted by DBear

Good info...I think I cut that off years ago when I starting stripping the frame down...i.e. the reason I am looking for pre-bent brake lines LOL.

Another member stated that I could use 1/2 or 3/4 ton pre-bent lines on my 1 ton 4x4, which he's definitely smarter than I on this situation. Have you seen that done before?

When I did lines on my GMT800 I used prebent for the front portion, but the rear portion needed to be straightened and re-bent in order to feed through the rails. I would have been as far ahead to use a straight section and then bend in place.

K

[GRADYS Performance]

Keith, Does this valve increase or decrease rear brake pressure as it operates thru it's height range?

Originally Posted by Keith Seymore

That height sensing valve was a Rube Goldberg-esque attempt at a mechanical anti lock brake system, before there was an electronic version.

It was specifically added to help meet MVSS Federal standards for stopping distance. Some test scenarios (combinations sorted by model, brake series, wheelbase, rear axle, tire type and curb vs GVW) were so tenuous that we would ask for a specific driver to run the test. We would run multiple tests and classify them as "development" until we got a pass and then categorize that one as "validation" and submit it to the Federal Government.

If you are not trying to meet federal stopping distance requirements by a within few inches then you could probably leave it off completely or, as suggested above, add a manual adjusting prop valve back there.

K

[Keith Seymore]

Originally Posted by GRADYS Performance

Keith, Does this valve increase or decrease rear brake pressure as it operates thru it's height range?

Yes.

So fully extended - it limits brake pressure above 150 psi at 43%.

With the linkage compressed (via suspension load) - it allows full pressure.

Assuming it is adjusted correctly and operating as it should.


K

[DBear]

Forgive me for my ignorance on this, but isn't there some kind of block that sits inside the front frame to which the brake lines connect to? Didn't think it is the proportioning valve, but I could be wrong.

I am talking about the the block that connects the crossover line, master cylinder lines, etc.? Thanks

[wildwilly4x4]

yes, there is "block" on the front of engine crossmember. That "block" is called a combination valve. This is combination of proportioning valve and a residual valve. They are a pretty generic part typically designed for either Drum/Drum, Disc/Drum, or Disc/Disc systems...front/rear respectively. A quick search on ebay will usually find you one for less than $50, I've found it difficult to lookup at local part stores sometimes. Obviously if you are going back with stock stuff, you will need Disc/Drum for a K30.

[DBear]

Originally Posted by wildwilly4x4

yes, there is "block" on the front of engine crossmember. That "block" is called a combination valve. This is combination of proportioning valve and a residual valve. They are a pretty generic part typically designed for either Drum/Drum, Disc/Drum, or Disc/Disc systems...front/rear respectively. A quick search on ebay will usually find you one for less than $50, I've found it difficult to lookup at local part stores sometimes. Obviously if you are going back with stock stuff, you will need Disc/Drum for a K30.

I did search propositioning valve, but when the part shows up, it doesn't say anything about combination valve or residual valve? Thank you again for your input sir

[DBear]

Originally Posted by wildwilly4x4

yes, there is "block" on the front of engine crossmember. That "block" is called a combination valve. This is combination of proportioning valve and a residual valve. They are a pretty generic part typically designed for either Drum/Drum, Disc/Drum, or Disc/Disc systems...front/rear respectively. A quick search on ebay will usually find you one for less than $50, I've found it difficult to lookup at local part stores sometimes. Obviously if you are going back with stock stuff, you will need Disc/Drum for a K30.

This is what I have found...seems that it is the combo proportioning valve/residual valve


https://www.ebay.com/itm/32552557136...CPbhbX8AaDRgQk