E-brake different from a 78 to a 80? .also proportioning valve question

[sircrunch]

I'm swapping the frame on a 1978 v8 big 10 shortbed. The donor frame is from a 1980 6 cyl shortbed.

So I'm finishing up and I noticed something strange when trying to put the e-brake cable back together. The ebrake cable part that hangs out of the firewall looks like it mounts to the chassis in a different location on this frame. You can see where the 80 model mounted, but the cable that comes out of the firewall on my 78 cab does not reach this bracket. Any advice?
Also, I'm keeping my Big 10 style brakes front and rear (heavier duty). I'd like to use the same brake lines including proportioning valve and everything from the 6 cyl regular duty brakes. Are they the same?

[sircrunch]

nobody knows either of these questions?

[Keith Seymore]

Sorry - didn't see this until now.

Yes - e brakes are different. Perhaps you could make a little "jumper" connector, out of wire (or with a mechanical bracket of some type), to bridge the extra distance.

We might need more detail on the prop valve/brake cylinder questions. I have the brake engineering release charts at home and will check when I get there, but might need to know (or figure out) JB1/JB3/JB5/JB6 for both the donor and recipient.

K

[Keith Seymore]

Turns out I don't have the '80 brake chart, although I have the '78, '79 and '81. I can use either the '79 or '81 chart as a sub, or - if they are the same - demonstrate the difference on the '78 chart.

Originally Posted by Keith Seymore

We might need more detail on the prop valve/brake cylinder questions. I have the brake engineering release charts at home and will check when I get there, but might need to know (or figure out) JB1/JB3/JB5/JB6 for both the donor and recipient.

But - we need more detail. The '78 Big Ten is pretty straightforward, with a GVW of either 6050 or 6200 lbs. Either of those result in a JB5 brake system.

The 80, however, spans from 4900 lbs to 6000 lbs GVW, which runs the full range of JB1, JB3 and JB5, which makes a pretty big difference in rotors, calipers, foundation brakes, apply system and prop valve.

Any way to determine the GVW rating of the '80 frame you have?

K

[sircrunch]

Neither one of my trucks have the stickers for GVW or RPO codes but I can tell you that the 1980 donor truck was just a very basic 2wd 6 cylinder truck with no air.... auto trans... light duty Springs and such as that it was a regular C10 ...it did have power brakes. Hope tthishelps

[Keith Seymore]

Originally Posted by sircrunch

Neither one of my trucks have the stickers for GVW or RPO codes but I can tell you that the 1980 donor truck was just a very basic 2wd 6 cylinder truck with no air.... auto trans... light duty Springs and such as that it was a regular C10 ...it did have power brakes. Hope tthishelps

Power brakes eliminates JB1, and drops it to either JB3 or JB5.

I'll take a look in a few minutes to see what effect that has.

K