1970 C60 brake concerns

[Nobighurry]

Looking for some input - I purchased a 1970 C60 ex-firetruck last year. It was converted to a flatbed farm vehicle sometime after 2011. The truck is in overall really good shape with only 35k miles. Since purchasing, I gutted the wiring and installed a AAW kit, got everything working (electrically speaking), converted it to HEI, replaced some other engine components to improve its road worthiness. Here's my dilemma, because the brakes are so important, i decided to have them gone through professionally by a big truck service center. They replaced the all 4 rear cylinders, inspected the fronts, shoes were in good shape. Replaced the vacuum booster. The master cylinder was replaced just before I purchased it. So here's the issue, the pedal is still very spongy. It has a very long reach before engaging. Once it engages, the stopping is sure and effective. While I don't expect the pedal to be as responsive as today's vehicles, I would expect it to be better than it is. Can anyone provide insight as to whether the described is accurate performance of the brakes? I appreciate all input

[txagincali]

Man I would be interested in seeing a photo as your truck sounds like it has had a similar life as mine I recently picked up (former fire truck turn utilitiy truck).

My thoughts are, and please confirm, if the master cylinder was replaced, is it still the single line unit? My feeling on those is you have to build up good pressure to the booster before the brakes actually engage, which is why the spongy feeling is there before the stop hits. Is it possible that it could be the wrong bore size?

[Richard2112]

Your brake system should work every bit as well as todays systems although That can't be said with front drums. They leave a bit to be desired. However, I found that on my 70, if the shoes weren't adjusted close, there was a lot of travel in the pedal.

[Nobighurry]

Thanks for the responses. I was thinking about checking the adjustment, but these Dayton wheels are a booger - heavy - to deal with. I really don't want to take it back to the previous shop as they killed me with a $1k bill the first time. I may just have to bite the bullet and pull the wheels.

Once I figure out how to add images, I'll post a few

[Nobighurry]

Here are a couple photos.

[sweetk30]

shoe's not adjusted up correctly ? these old style can have upper AND lower adjustment points .

and lots of guys can miss the bleeder screw on the booster under the cab that's way up top and almost hiding . I know I did the first time I worked on 1 of these units . got lots of air out of it .

some of them have a bleeder on the firewall master that's REAL TINY also .

make sure the vacuum booster supply line from the engine has a good working check valve also . this will give low / crappy brake pedal .

these are the first few things I would look at .

[Nobighurry]

Thanks for input. I'm going to try the check valve you referenced. I'm sure they didn't replace it. If no help, I'll re-bleed the entire system. I hope it's one of those. I really don't want to pull those heavy wheels/drums off.

[sweetk30]

check the drums for a tiny hole in the upper face just before the 90* turn to the surface area .

my truck i worked on had a hole in each drum to let you see the shoes in relation to the drum face to check adjustment . all you had to do was jack up each wheel and rotate to line up and adjust from there as needed.

but this could have been some home brew thing some old timer did way back in the day with a drill .

[Nobighurry]

So did a little inspecting - I don't have the check valve on the main vacuum line coming from the engine. Its a large line - probably 7/16 or 1/2 - from visual inspection. Heck it may be larger than that - memory is going.

[c60clf]

I think the check valve only prevents gas fumes from entering booster and also prevents fumes in cab where vent should be,maybe also check and make sure vacuum hoses are heavy duty and not collapsing.hope this helps

[c60clf]

I think the check valve only prevents gas fumes from entering booster and also prevents fumes in cab where vent should be,maybe also check and make sure vacuum hoses are heavy duty and not collapsing.hope this helps